The Power of Zero

Samuel's picture

The Power of Zero
Category: School, College, Greek

Samuel Thomas Poling, Blog 124, The Power of Zero

This is an essay I turned into my college math instructor last week. She has said "it's an enjoyable read," but hasn't finished it yet, nor commented further.

Samuel Thomas Poling

October 30, 2006 A.D.

Math

The Power of Zero: The Mistake

Math is a world of logic, nothing more. Many contend that logic and math are different things, but math is just a certain area of logic to do with amounts, values, and things around that area. To navigate any mathematical problem you must rely on reasoning. Every theorem and shortcut must be provable within the world of logic. This is math. Anything else, anything else at all, can never be used to support a mathematical idea. Not desire, not how many people believe it, not by who said it to be true – only logic can say what works and what doesn't.

Another thing one must realize about mathematics is that it's simply a language. The sequence 1 + 1 = 2 appears as words in our minds. They are symbols used to represent values and processes. There are not actually any 1s floating around, nor are there any 2s. There isn't a great plus sign in the sky whose power you summon – to satisfy the deity of equals. They don't actually exist, they are just ideas used to make logical statements about amounts and so forth. With another luck we might have evolved to use the label of division in place of addition, or the word three in place of the word four. It doesn't matter; these numbers and sequences are just ways of explaining our reasoning.

One such method of explanation has been the mathematical method of powers. Exponents. You have a base number, like any other number, with another smaller number floating next to it, top right. What does this say to the human race in mathematical language? What did we decide to make that mean? The exponent, the power, the smaller number floating above, is meant to tell you how many times the base number should be multiplied by itself. That's what it means, clear and simple. It's a shorter way of writing something out. Instead of 3 * 3 * 3, you can simply write 3^3. As I type this, I couldn't find the ability to make the exponent float up next to the base on Microsoft word, but fortunately the "^" symbol works in mathematical language as well. 3^3 means 3 to the power of 3. Which means 3 multiplied by itself 3 times. If it were to the power of 4, then it would be 3 multiplied by itself 4 times, or 3^4. It's quite simple.

So following what powers have been made by our human race to represent, we can figured out what 3^3 would be. 3 * 3 * 3 = 27. Ergo, 3^3 = 27. What about 3^2? Easy, it is telling you the number 3 twice, multiplied. 3 * 3. And that is equivalent to 9. How about 3 to the power of 1? Easy again, that's three one time. Having nothing to multiply to, it is just left as three. 3^1 = 3. This is how it is contended by all.

What is a number to the power of zero equal to? Currently mathematicians hold it to be true that it is equal to one. No matter what the base number is, if the exponent is zero, then it is equal to one. However, if you follow the same reasoning of meaning we have given exponents to possess, then we see a different picture. 3^0 would be 3 zero times. Having nothing to multiply to, we are left with zero, and not with one. Following the same pattern, the same meaning, the same logic as we have with 3^2 = 9, and 3^1 = 3, we arrive at 3^0 = 0. Why? 3^2 is two 3s. 3^1 is three 3s. And 3^0 would be no 3s. "To the power" means you multiply the base by itself the number of times shown by the exponent. If you have 3^0, the exponent is telling you that you have no 3s to multiply together. This is just using common sense. To refute this, you need some pretty special and pretty solid evidence.

The math world thinks it has found the evidence. I have scoured online and off, hearing several supposed "solid" proofs for 3^0 = 1, but I have seen flaw in all of them so far. A common flaw at that. It's difficult to explain, but it's there. To show you what I mean, I'll have to first express to you the supposed proofs they have mustered together.

The world of exponents has several short cuts. Short cuts can be found in math all of the time. However, initially they are risky. You see, you have to have proof the shortcut works. You must solve the problems the long, hard, usual, certain way as well as the short cut way, and check them together to make sure they arrive at the same solution. You must not only check these short cuts in many different areas (positive, negative, fraction, decimal, zero, even, odd, ect.) to make sure the cut holds true, but you must also be able to explain why it is a short cut, and how it works the way it does. You must mathematically prove it. This is pretty much been done well with the exponent short cuts, now called exponent "rules."
This leads me directly to the first problem with the evidence asserting a number to the zero power equaling one instead of zero. You must prove a short cut with the long, normal way of doing things, not the other way around. Although the thinking, reasoning, long-cut way of 3^0 claims that it equals zero with common sense and definition of exponent, the short cut says otherwise. It is in the shortcuts where 3^0 will equal one. And only in the short cuts. I would normally expect you to then realize that there is something incomplete with the description of the short cut! However the math world made a mistake and instead of fixing their short cuts, they used the faulty short cuts to change reality.

Let's say I say to you there is a faster way of solving a division problem. I just switch the denominator with the numerator and subtract, and then claim it was just a short cut. You do the long-cut, more difficult (yet more trustworthy) way of dividing something, and you notice we get different answers. But instead of me changing my short cut, I change the usual laws of division. What is my proof to back up my insanity? My short cut. This is, of course, rediculous backwards reasoning.

Yet this is exactly how the mathematicians are trying to prove 3^0 = 1.

They have faulty short cuts, and when it is discovered these short cuts don't work in the case of zero, which many short cuts in math do not, instead of adding it to the rules of exponents, the change the reality.

Here is the most common "proof" of 3^0 equaling 1:

There is an otherwise proven short cut exponent "rule" that says when you are multiplying two numbers of the same base, you can just add the exponents. For example, if you have (3^3) * (3^2). They have the same base, it is 3. Ergo, says the short cut, you can easily add up their exponents and just put it over the base. So (3^3) * (3^2) = 3^5, because 3 + 2 = 5. Would this trick work in the case of (3^3) * (4^3)? No, because, as you can clearly see, the bases are not the same. For this rule to work, the bases must be the same. Base 3 is not the same as base 4; the shortcut does not apply here.

Understand? Alright, so lets get right to it and see how an exponent of zero will play the part. (3^3) * (3^0) will be our problem. It has the same base, doesn't it? They both have the base of three. Ergo, the shortcut says we can go ahead and add the exponents. So we will end up with 3^3, right? Wait, if what I said is true, then we should end up with zero! (3^3) * (3^0) should equal zero, if what I said is true, because 3^0 = 0. And anything by zero will be zero. The shortcut proves me wrong. Or does it? It proves me wrong the same way my example division "short cut" proves division wrong. But let's see, if any number to the zero power does, in fact, equal one, then the short cut isn't broken, because any number, including 3^3, by one should equal itself, as it was shown above to actually happen. The short cut really does work against me well, doesn't it? No wonder so many math experts believe a number to the power of zero equals one.

But again, I assert there is an exception with zero being in one of the powers. There are several mathematical rules and short cuts with exceptions to zero, many of which are other exponent rules themselves. For example, 0^0 can't equal one, can it? There's an exception there, isn't there? The shortcut is incomplete; it needs to add an exception to zero being in one of the powers.

Although, it isn't so much incomplete. Just saying there is an exception to zero would make it easier for students to learn this. The rule, as it stands, already says that (3^3) * (3^0) = 0. You just have to look more closely. Pay attention, this is my trump card. When multiplying two numbers with exponents, you can only use the short cut if both the bases are the same, as I explained earlier. However, in the case of (3^3) * (3^0), the bases are not actually the same. It's an illusion.

Here is the part that is the most difficult to explain. Once this is a shortcut, it can't really prove one way or the other, 3^0 = 1 or 0. Circular reasoning will enter into this if you try to use it to prove one way or the other. But I'm not trying to prove 3^0 = 0 right now, I'm only trying to disprove 3^0 = 1. Show another possibility. So pay attention as I bring this to even ground. If I am right, then 3^0 = 0. In which case the base numbers are not the same and you cannot use the short cut, but the short cuts own rules! "Oh, but both base numbers are 3!" No, they're not. It just appears that way. If I am right, then 3^0 = 0, which is not at all the same base number as 3. Writing it in 3^0 to begin with was a stupid way. If I am right, then 3^0 = 4^0 and any other number you want to put in front of the zero power! (3^3) * (3^0) is really (3^3) * (X^0), X being any integer. Ergo, they do not, in reality, have the same base. And if that isn't good enough for you, then look at another mathematical process. You can write 3^3 out nicely. By the definition of powers, 3^3 is telling you 3 multiplied by itself 3 times. So 3 * 3 * 3. Looking at the definition of powers, 3^0 means 3 multiplied by itself never. So nothing. So multiplying 3 * 3 * 3 by nothing gives you nothing. Ergo, the short cut still doesn't work, in the case of the raw definitions and meanings of powers. What exponents mean testifies against 3^0 = 1, and testifies for what I say to be true.

"But 3^0 doesn't equal 0, it equals 1!" Shouts the mathematician, falling into circular reasoning. They put in (3^3) * (3^0) and get 1 due to the short cut. They take apart the numbers as 3 * 3 * 3 * 1, again getting the solution of 3^3, meaning 3^0 equaling one works! They're using circular reasoning. They are using what they are trying to prove as part of the proof for that thing. They are assuming 3^0 = 1 being true as they are trying to prove it. When you ask them to prove to you 3^0 = 1, and they, in the proof, use 3^0 equaling one, then they are guilty of circulus in demonstrando. Circular reasoning, circular argument. Until they have proven it to you, assert and reassert that as of now 3^0 = ?. And they have to deal with that until they've proven otherwise. They'll slap 3^0 = 1 somewhere in their "proof" but you just snap their attention back to the fact that right now, until they've proven it, 3^0 = ?, not yet 1. Not until they've proven it.

But isn't circular reasoning what I was doing above? I said, "If I'm right," a few times up there, that's true. But as I said, I wasn't trying to prove 3^0 = 0, I was only trying to show that there is not yet any proof that 3^0 = 1. If they can, in their proof, slap in 3^0 = 1, then I can, in my proof, slap in 3^0 = 0. If they attack me on that, I can correctly accuse them of special pleading and hypocrisy.

Where, then, do the tables turn? In the common sense. Where I did in fact prove 3^0 = 0 was much earlier on, with the very simple description of what powers are created to mean. How many of the base numbers are being multiplied together. If there is none, then there is none. There is zero. Following the same reasoning and definitions of all the other exponents, a number to the zero power will be equivalent to zero. This is where the tables turn.

The others "proofs" I've looked at for 3^0 = 1 are other variations of the same one I just destroyed, as common sense can clearly see. Instead of putting in 3^0 = 1 in any of their proofs, go ahead and try 3^0 power, apply my same logic, and you'll see it could work that way to. There is that exception to zero, there is that fact that it isn't actually the same base, and so on. If they say that any number over another number is equal to one, and then put 3^0 over 3^0 on a fraction bar, then just write zero over zero next to that, and ask them if that equals one. (3^0) / (3^0) = 0 / 0, which does not equal 1. Hey, they could assume 3^0 = 1 in their proof, why can't I assume 3^0 = 0 in mine? I also have the bonus of the common sense and the actual meaning of exponents on my side. I'm actually more justified.

There may be evidence that a number to the power of zero is truly one, but my main point here today is that I have not seen it. I heard dozens of experts, viewed several sites, heard my math instructor, herself, explain it to me. However, their evidence is not conclusive. If they are right, they haven't proven it yet. If it does not equal zero, which I very well may not, then that doesn't mean this essay was wrong. I'm pointing out the flaws currently being made. And also pointing out that, as of now, my side is more justified. I also understand that this would change everything greatly, so close mindedness to my entire argument here by mathematicians is unfortunately likely. But their complaining would change anything until they have some conclusive proof.

So, in closing, there is a big mistake. A mistake of circular reasoning, using what you are trying to prove as part of the proof for that thing. A mistake of backwards reasoning, using short cuts to change reality, instead of reality to fix short cuts. There is no proof for 3^0 = 1, that isn't fallacious. My math instructor once told me to take 3^0 = 1 on faith. Only error needs the assistance of faith. If, in math, it's true, it can be proven logically, and, as it is so far, it has not yet been proven to me. Much we can learn from our teachers, more from our colleagues, but the most from our students.
Doubt everything.

Samuel Thomas Poling, Blog 124, The Power of Zero

This is a second response to

This is a second response to BobSpence1:
 

In your attempted

Submitted by BobSpence1 on November 9, 2009 - 5:05pm.




You write:

"For someone who comes across as very insistent on precise definitions, to use such a sloppy and downright wrong definition for exponentiation displays very poor thinking skills."

 

I guess that I am just repeating myself here, but what makes you think that I was using "such a sloppy and downright wrong definition for exponentiation"? I was doing no such thing. I was taking as a premise this "sloppy and downright wrong definition for exponentiation" for an argument which shows the logical consequences of taking this "sloppy and downright wrong definition for exponentiation" as a definition of exponentiation.

(With a little more work at defining what it means to multiply A by itself n times (for n greater than 1, n = 1 and n = 0) (the kind of work that is needed to turn your definition involving repeated multiplication by A and Wikepedias definition into a definition that works for integer n = 1 and n = 0, as well as for any integer n greater than 1) this "sloppy and downright wrong definition could be turned into a correct definition of A^n. Indeed, depending how one defines multiplication of A by itself 0 times, I'm sure that Samuel could come up with a definition for which A^0 = 0. Having such a definition would not make Samuel either sloppy or wrong. It would just mean that he is using a different definition of exponentiation (i.e. a different concept of exponentiation) than mathematician's use. I think that he would probably have a hard time convincing people to study his concept, but he certainly would not be a target for a charge of being sloppy and downright wrong. One cannot be wrong about a technical definition. In making a technical definition one is simply telling everyone how one is using a term. Sloppiness can only be charged when the definition is not determinative of a meaning.)

 

Again, I don't see how you make the step from my using a premise for an argument to getting that I was using the premise as a definition. Apparently, you think that you can make this step; otherwise why would you be carrying on about how sloppy, downright wrong, and even inconsistent I was being?

 

Sincerely,

Dr. John D. McCarthy

 

 

 

BobSpence's picture

Re definition:I apologise I

Re definition:

I apologise I quoted where I was considering the definition of exponentiation, rather than A0 itself.

I should have referred to this post:

 

Exponentiation of A by zero is defined as corresponding to no operation at all, making it consistent with both above definitions, ie, neither multiplication or division is actually involved.

 

Wikipedia wrote:

 

Notice that 31 is the product of only one 3, which is evidently 3.

Also note that 35 = 3·34. Also 34 = 3·33. Continuing this trend, we should have

31 = 3·30.

Another way of saying this is that when n, m, and n − m are positive (and if x is not equal to zero), one can see by counting the number of occurrences of x that

 \frac{x^n}{x^m} = x^{n - m}.

Extended to the case that n and m are equal, the equation would read

 1 = \frac{x^n}{x^n} = x^{n - n} = x^0

since both the numerator and the denominator are equal. Therefore we take this as the definition of x0.

Therefore we define 30 = 1 so that the above equality holds. This leads to the following rule:

> Any number to the power 1 is itself.

> Any nonzero number to the power 0 is 1; one interpretation of these powers is as empty products.

 

 

IOW, the definitions for the cases where n = 1, 0, and negative, (and non-integer, of course), are chosen so as to be as mathematically consistent as possible with the basic definition for non-zero exponents greater than 1.

 

 

Favorite oxymorons: Gospel Truth, Rational Supernaturalist, Business Ethics, Christian Morality

"Theology is now little more than a branch of human ignorance. Indeed, it is ignorance with wings." - Sam Harris

The path to Truth lies via careful study of reality, not the dreams of our fallible minds - me

From the sublime to the ridiculous: Science -> Philosophy -> Theology

BobSpence's picture

You and Samuel are the only

You and Samuel are the only ones who have used the expression "A^n is the result of multiplying A by itself n times.", and it is not valid.

Using that to demonstrate a fallacy is a straw man, and irrelevant to anything I have written.

 

Favorite oxymorons: Gospel Truth, Rational Supernaturalist, Business Ethics, Christian Morality

"Theology is now little more than a branch of human ignorance. Indeed, it is ignorance with wings." - Sam Harris

The path to Truth lies via careful study of reality, not the dreams of our fallible minds - me

From the sublime to the ridiculous: Science -> Philosophy -> Theology

(No subject)

Oops! I left out something

Oops!

I left out something from my definition of a^n (the mathematician's definition) which I had included in my earlier posts.

What I should have written was what I wrote in an earlier post:

DEFINITION: (i) a^0 = 1 for every nonzero real number a

(ii) a^1 = a

(iii) a^{n + 1} = (a^n)(a) for every positive integer n

(iv) a^{-m} = 1/(a^m) for every positive integer m and every nonzero real number a

 

I mistakenly left off the last clause "every nonzero real number a".

 

I apologize for this oversight.


Sincerely,

Dr. John D. McCarthy

 

This is a response to

This is a response to BobSpence1:

Re definition:I apologise I

Submitted by BobSpence1 on November 9, 2009 - 9:05pm.

 

You quote yourself earlier:

"Exponentiation of A by zero is defined as corresponding to no operation at all, making it consistent with both above definitions, ie, neither multiplication or division is actually involved."

How does this phrase "corresponding to no operation at all" allow you to say "Exponentiation of A by zero is defined as ..."? 

I can understand how someone could say something like "The definition of exponentiation of A by zero shows that exponentiation of A by zero corresponds to no operation at all." Call me slow, if you wish, but I don't understand how one can say that "Exponentiation of A by zero is defined as corresponding to no operation at all".


The best interpretation which I can think of for this statement is "Exponentiation of A by zero is defined so that it corresponds to no operation at all."

Perhaps, you have a different interpretation of this statement than I have been able to get. I would be interested in hearing it.

 

Since I am unable to see how "Exponentiation of A by zero is defined as corresponding to no operation at all", nor how that makes it "consistent with both above definitions, neither multiplication of division is actually involved.", it is my distinct impression that by this statement "Exponentiation of A by zero is defined as corresponding to no operation at all, making it consistent with both above definitions, ie, neither multiplication or division is actually involved." you have not defined A^0.

 

As I said, perhaps you have an interpretation of this statement than I have been able to get. Again, I would be interested in hearing it.

 

By the way, I suppose that I am showing how out of touch I am, but I don't know what "IOW" means.

 

I can see, as I indicated in my earlier post, that the Wikepedia article was careful to define x^0.  I already apologized for not recognizing the care with which Wikepedia handled the definition of x^0.

 

Sincerely,

Dr. John D. McCarthy

 

 

 

This is a response to

This is a response to BobSpence1:

You and Samuel are the only

Submitted by BobSpence1 on November 9, 2009 - 9:11pm.

 

You write:
 

"You and Samuel are the only ones who have used the expression "A^n is the result of multiplying A by itself n times.", and it is not valid."
 

Fair enough. As I said, the mistake I made was in assuming that, since you did not challenge Samuel's definition of A^n, but only went on to give your argument for A^0, I assumed that you were willing to live with Samuel's definition.


I apologize for making this assumption.

 

 

I did not assume that when Samuel said that A^n is the result of multiplying A by itself n times that he meant anything other than that to calculate A^n you take n factors of A and multiply them. It is pretty obvious that that is what Samuel meant since he pointed out that 3 * 3 * 3 = 3^3 and 3 * 3 = 3^2, even though he said "The exponent, the power, the smaller number floating above, is meant to tell you how many times the base number should be multiplied by itself." I gave him the credit that by "how many times the base number should be multiplied by itself" he meant how many times you take the base number as a factor of your product.

I agree with you that this is not using the term "multiplied" correctly.
 

You write;

"Using that to demonstrate a fallacy is a straw man, and irrelevant to anything I have written."

 

I don't believe that I demonstrated a fallacy. The best that I can get out of what I demonstrated is that the premises of my argument have a certain conclusion; a conclusion which is inconsistent with the desirable definition: A^0 = 1 (a definition to which Samuel is apparently not attracted). Perhaps, I'm missing something about my own argument.

 

I have already indicated that the mistake I made was in trying to guess what your definition of A^0 was. Hence, my demonstration is not relevant to what you have written. I have already apologized for having made this guess.

 

Now I wish to return to another issue which I was addressing in my recent posts.

 

How do you get from my using Samuel's definition as a premise for an argument that I was being sloppy, downright wrong, and inconsistent with my own definition of A^n?

How do you get from my using Samuel's definition as a premise for an argument that I was defining A^n as being the result of multiplying A by itself n times?

I made it very clear that that was not my definition of A^n.


So, as they say, "what gives"?


Sincerely,

Dr. John D. McCarthy 

 

 

 

 

BobSpence's picture

BTQ (= By the Way), IOW  =

 

BTW (= By the Way), IOW  = In other words.

And now for your 'argument':

===================

ARGUMENT: Suppose that n is a non-negative integer and two assumptions hold: 


(i) A^n is the result of multiplying A by itself n times. ==> Error: A^n is the result of multiplying A by A n-1 times, where n > 1, eg A x A is multiplying A by itself 1 times and is equivalent/equal to A^2. The cases for n <= 1 are what is being investigated

(ii) B * A^n is the result of multiplying B by A n times

(iii) multiplying B by A zero times is equivalent to not executing the operation of multiplication of B by A.

Then A^0 = A.

PROOF OF ARGUMENT. Let: 

(a) B = A. 

By assumption (i): 

(b) A^0 is the result of multiplying A by itself zero times. ==> Error: not valid, since  n < 1 for this definition - it would require A to be multiplied by A  -1 times, which is certainly not defined, although it could be defined as dividing A by A 1 time.

By assumption (ii),

(c) B * A^0 is the result of multiplying B by A zero times.

By (a) and (c): 

(d) A * A^0 is the result of multiplying A by A zero times.

Since A is equal to itself, (d) implies that: 

(e) A * A^0 is the result of multiplyiing A by itself zero times.

By (b) and (e): 

(f) A^0 = A * A^0.  ==> Error: (b) is not valid for n == 0, so (f) is not valid

Now by (iii): 

(f) the result of multiplying A by itself zero times is A: 

By (e) and (f): 

(g) A * A^0 = A. ==> Error: (f) is not valid, so (g) is not valid


By (f) and (g) and transitivity of equality: 

(h) A^0 = A. ==> Error: (f) and (g) are not valid

END OF ARGUMENT So I have pointed out the original error, and its propagation through the rest of the 'argument'.

 

 

 

 

Favorite oxymorons: Gospel Truth, Rational Supernaturalist, Business Ethics, Christian Morality

"Theology is now little more than a branch of human ignorance. Indeed, it is ignorance with wings." - Sam Harris

The path to Truth lies via careful study of reality, not the dreams of our fallible minds - me

From the sublime to the ridiculous: Science -> Philosophy -> Theology

BobSpence's picture

Ok, but your argument

Ok, but your argument produced a 'wrong' result for A0, because one of the initial assumption was explicitly invalid, and all you had to do was point out to Samuel that point, as I spelled out in my comment on that assumption.

To construct an argument with that initial assumption is like making one of your initial assumptions (in some other argument) something like " 1 == 2". The rest of the 'argument' is a waste of space.

It was certainly not relevant to me, since I never used it.

 

Favorite oxymorons: Gospel Truth, Rational Supernaturalist, Business Ethics, Christian Morality

"Theology is now little more than a branch of human ignorance. Indeed, it is ignorance with wings." - Sam Harris

The path to Truth lies via careful study of reality, not the dreams of our fallible minds - me

From the sublime to the ridiculous: Science -> Philosophy -> Theology

BobSpence's picture

Arrgh - I find it a fun

Arrgh - I find it a fun challenge to try and get people like this to get it...

 

Favorite oxymorons: Gospel Truth, Rational Supernaturalist, Business Ethics, Christian Morality

"Theology is now little more than a branch of human ignorance. Indeed, it is ignorance with wings." - Sam Harris

The path to Truth lies via careful study of reality, not the dreams of our fallible minds - me

From the sublime to the ridiculous: Science -> Philosophy -> Theology

This is a response to: BTQ

This is a response to:

BTQ (= By the Way), IOW  =
Submitted by BobSpence1 on November 10, 2009 - 12:33am.

 
You write:

"ARGUMENT: Suppose that n is a non-negative integer and two assumptions hold:


(i) A^n is the result of multiplying A by itself n times. ==> Error: A^n is the result of multiplying A by A n-1 times, where n > 1, eg A x A is multiplying A by itself 1 times and is equivalent/equal to A^2. The cases for n <= 1 are what is being investigated"


You've gotten off to a poor start here. Once again, you are attempting to show that my argument is erroneous by challenging the premise. This is an attempt to do something which is not possible. The premise of an argument does not have to be valid in order for the argument to be valid. Demonstrating that the premise "x + 1 = x" of the argument "If x + 1 = x, then x + 2 = x + 1." is an erroneous premise in no way undermines the validity of the argument that "If x + 1 = x, then x + 2 = x + 1.". As I pointed out in my previous post, there is a very simple completely logically sound argument that "If x + 1 = x, then x + 2 = x + 1.". Pointing out that x + 1 is not equal to x, in no way undermines the validity of this completely logically sound argument.

Apparently, you think that it does. As I pointed out in my previous email, whether you think that it does or not I don't know (but it certainly appears that you do), does not represent good "thinking skills".


I have already conceded that the premise of my argument is not relevant to what you have written.


I also agree that the premise "(i) A^n is the result of multiplying A by itself n times." has not been defined clearly. But, if this is the problem which you are having with the argument, you could simply ask me how I am defining multiplication of A by itself n times. I really have not attempted to define this phrase, but from what Samuel said about it I assume that he meant that you take 0 factors of A and "multiply" them (whatever that means). Apparently, whatever Samuel understands this to mean something; and, whatever he means by it, I'm wiling to assume that it gives him 0.

 

Again, I understand that this is not relevant to what you have said. I'm sorry to waste your time and mine by giving this argument. I guess that I should have addressed it to Samuel. At least it serves the purpose of showing that two assumptions (i) that A^0 is the result of multiplying A by itself 0 times and (ii) that B * A^0 is the result of multiplying B by A 0 times yield the conclusion that A^0 = A. Hopefully, this would show Samuel that if he wants to have A^0 to be equal to 0 he has to explain how he is interpreting statements (i) and (ii) so that they don't together imply that A^0 = A.


Sincerely,

Dr. John D. McCarthy

 

This is a response to

This is a response to BobSpence1:

 

 

Ok, but your argument

Submitted by BobSpence1 on November 10, 2009 - 12:48am.

 

You write:

"To construct an argument with that initial assumption is like making one of your initial assumptions (in some other argument) something like " 1 == 2". The rest of the 'argument' is a waste of space."

 

Apparently, you don't appreciate the power of a proof that starts with a questionable (or even false) assumption and derives a consequence from it. Such an argument is not "a waste of space". It serves the purpose of demonstrating where the assumption leads.

 

Such arguments are frequently used in proving some of the most famous theorems of mathematics (theorems which you apparently would regard as "a waste of space&quotEye-wink.

 

Now I wish to return to another issue which I was addressing in my recent posts.

 

How do you get from my using Samuel's definition as a premise for an argument that I was being sloppy, downright wrong, and inconsistent with my own definition of A^n?

How do you get from my using Samuel's definition as a premise for an argument that I was defining A^n as being the result of multiplying A by itself n times?

I made it very clear that that was not my definition of A^n.


So, as they say, "what gives"?

 

I must admit, I guess I also am interested in the challenge of trying to get people who make erroneous arguments to get it.


It's one of the things that I am frequently engaged in when teaching my students how to make a rational argument.

 

Sincerely,

Dr. John D. McCarthy 

This is a response to

This is a response to BobSpence1:
 

Arrgh - I find it a fun

Submitted by BobSpence1 on November 10, 2009 - 12:53am.



You write:

"Arrgh - I find it a fun challenge to try and get people like this to get it..."

 

Please don't waste my time and yours with trying to get people like me to "get it".

 

I think my abilities to get it speak for themselves.

 

I think that the judgement of my peers has much more weight than your judgement has shown to have by your reasoning (e.g. the use of a premise in a proof gives you space to say that the person who used the premise in the proof was contradicting himself when elsewhere he accepted somethiing contradictory to that premise).

 

One of my peers, who was given the highly distinguished honor of giving a main address to the International Congress of Mathematicians by demonstrating his ability to get it, said of me that I was the most logical person he had ever met.

 

Another one of my peers, who has received equally prestigious honors for his ability to get it, said of me that "If McCarthy accepts a proof, then it must be correct.". This peer's opinion of me formed part of the basis for my being promoted to Professor of Mathematics.

 

My student comments bear testimony to my ability to get it.

 

Sincerely,

Dr. John D. McCarthy

BobSpence's picture

The logical validity of an

The logical validity of an argument does mean it is telling us anything useful. This is clearly the case in the example you give.

All that really demonstrates is that if you start with a false premise you can come to a false conclusion. I think we already knew that.

The situation with respect to the premise "A^n is the result of multiplying A by itself n times." is not just a matter of it being not defined clearly.

The more I look at it, and taking your description of multiplication as a binary operation, it is actually defined quite well enough, and it is in direct conflict with the basic definition of exponentiation on at least two points. 

1. It does not restrict its domain of validity with respect to the values of n, which at the very least should be for positive integers > 0.

2. It conflicts with the standard basic definition of exponentiation, which requires n factors, not n multiplications.

You have demonstrated that this particular definition allows you to 'conclude' that A0 = 0, which is showing the same thing Samuel did, perhaps more rigorously. Which is of no real assistance in clarifying for Samuel just what his error was.

Ny argument:

Quote:

(i) A^n is the result of multiplying A by itself n times. ==> Error: A^n is the result of multiplying A by A n-1 times, where n > 1, eg A x A is multiplying A by itself 1 times and is equivalent/equal to A^2. The cases for n <= 1 are what is being investigated.

is the sort of argument that would be useful to show his error far more directly. NOTE: this is the sort of thing you manifestly failed to "get". 

Your approach is just as likely to reinforce his erroneous assumption, depending how he reads it.

 

Favorite oxymorons: Gospel Truth, Rational Supernaturalist, Business Ethics, Christian Morality

"Theology is now little more than a branch of human ignorance. Indeed, it is ignorance with wings." - Sam Harris

The path to Truth lies via careful study of reality, not the dreams of our fallible minds - me

From the sublime to the ridiculous: Science -> Philosophy -> Theology

BobSpence's picture

OK, so you were using that

OK, so you were using that to show that that his erroneous assumption lead to his conclusion. But as I pointed out in my previous post, even if this has some mathematical validity, it is probably worse than useless in pointing out his error.

So, whatever your math credentials, you appear to fail miserably in understanding how to approach correcting such misconceptions. Arguing in such subtle and pedantic ways, especially when there is a much more straightforward way to point out the error, as I showed, is not the way to go. 

I suspect now that the level at which you study math is actually hampering you in addressing errors at this level.  Such a style is simply going to go straight over the head of the mathematically naive, who are precisely the people who will make such errors.

It looks like this is at the heart of our disagreements here.

Do you address students who are starting with very little math background? Your approach may well work if your students are already at a relatively advanced level.

Favorite oxymorons: Gospel Truth, Rational Supernaturalist, Business Ethics, Christian Morality

"Theology is now little more than a branch of human ignorance. Indeed, it is ignorance with wings." - Sam Harris

The path to Truth lies via careful study of reality, not the dreams of our fallible minds - me

From the sublime to the ridiculous: Science -> Philosophy -> Theology

This is a response to

This is a response to BobSpence1:

 

OK, so you were using that

Submitted by BobSpence1 on November 10, 2009 - 3:42pm.

 

You write:

"I suspect now that the level at which you study math is actually hampering you in addressing errors at this level.  Such a style is simply going to go straight over the head of the mathematically naive, who are precisely the people who will make such errors."

 

Apparently, from what you tell me about your original argument, I missed what you were doing in your original arguments in response to Samuel. Even now, when I go back and read what you actually wrote, I find it very difficult to believe that you were not doing what I thought you were doing. The arguments which you gave at that point are not presented in the form of a  motivation for defining A^0 to be equal to 1. They are presented as an argument that A^0 is equal to 1. 

 

For instance:

"Multiplying any number A by

Submitted by BobSpence1 on November 6, 2009 - 7:42am.

Multiplying any number A by any number B zero times leaves A unchanged:

A  *  (B0) = A 

Therefore (B0) = A/A = 1."

 

This argument has all the hallmarks of a deduction, not a motivation. The colon indicates an equivalence; what comes before the colon is presented as implying what comes after the colon. It appears as if it is saying:

STATEMENT: Multiplying any number A by any number B zero times leaves A unchanged. That is to say, A  *  (B0) = A.

 

I can believe that this is not what you intended to do; but I think that it is fair to say that it certainly appears that way. If this is not what is being done, then how did you get from what comes before the colon to what comes after the colon?

 

I think that since this is what this argument appears to be saying, that it does not challenge Samuel at all. I am pretty sure that his reaction to this argument would be the same as his reaction to other "proofs" that A^0 = 1 that he was getting from his instructors and other people he went to in order to find out why A^0 = 1. Namely, he would see this argument of yours as circular reasoning. In order to justify what comes after the colon as following from what comes before the colon you have to assume that multiplication of any number A by B^0 is the same thing as "Multiplying any number A by any number B zero times". I'm pretty confident that Samuel would ask himself the same question that he asked himself about the "proofs" which people offered him. Namely, how are you getting the thing which comes after the colon from the thing which comes before the colon. I'm pretty sure that Samuel would say that this is done by assuming that a pattern which holds for positive integers also holds for the integer 0; an assumption which Samuel rightly points out does not have to be valid. This is one of the germs of truth in Samuel's argument; pattern which hold for positive integers don't have to hold for positive integers and 0. He rightly points out that there are patterns which have exceptions. So why shouldn't the pattern that: 

(1) A * (B^3) is the same thing as multiplying A by B three times,
(2) A * (B^2) is the same thing as multiplying A by B two times,
(3) A * (B) is the same thing as multiplying A by B one time,

break down when we get to multiplication of A by B^0? This is actually a very good question that Samuel asks. Indeed, why shouldn't it break down? Why should we expect anything different than that it might break down? Samuel had seen a number of fallacious attempts at showing that A^0 = 1, all of which were based upon an unwarranted assumption that a certain pattern (which Samuel refers to as "the shortcut&quotEye-wink were sustained when we get to the power of zero. Samuel rightly saw that these arguments were circular reasoning.

 

I don't think that Samuel would have seen your argument as anything different. I think that he would have seen your argument as just another example of circular reasoning; just another example of making an unwarranted assumption about a pattern being sustained.

Hence, unlike your evaluation of my response to Samuel, I think that my response to Samuel was much more to the point. I cleared the mathematician of the false charge by Samuel of circular reasoning, by pointing out that mathematicians do not attempt to prove that A^0 = 1; and explicitly offered a motivation for why mathematicians define A^0 to be equal to 1.

 

In my estimation, my answer to Samuel was much more likely to have a chance of persuading Samuel of the benefits of defining A^0 to be equal to 1; while at the same time clearing mathematicians of Samuel's false charges of circular reasoning.

 

I'm sorry. I simply don't agree with your analysis of whose approach to Samuel's post stood a better chance of convincing Samuel that the more desirable course is to define A^0 to be equal to 1.


I agree that had you couched your argument in the form of a motivation rather than in the form of a proof then you would have come across as doing essentially the same thing I was doing; namely, providing a motivation for defining A^0 to be equal to 1. You may not agree with this, but I think that what you actually said comes across as a proof that A^0 is equal to 1, not as a motivation for defining A^0 to be equal to 1.

 

You write:

 

"Do you address students who are starting with very little math background? Your approach may well work if your students are already at a relatively advanced level."


The lowest level at which I deal with students is at the level of calculus. But some of these students come into my class with poor algebra skills, never mind skills with, say, geometric proofs. (I think that the sort of two-column proofs which I learned as a junior high student have been left out of at least some of these student's pre-college education, if not all of them.)

 

For the last several semesters, I have been teaching first semester freshman calculus. I require the students to justify all of their solutions by giving sound arguments. They are not required to write out detailed arguments, but only to indicate what needs to be done to get a sound argument. Some of my students have told me that this has really helped them to get a hold on the material. Others I think are just bothered by this requirement.

 

So, for the past several semesters, I would not say that I am dealing with students at an advanced level. But I teach them about such things as the direct method of proof of a conditional statement (assume the hypothesis and then deduce the conclusion); the logical fallacy of backwards reasoning (claiming that one has established a conditional statement by assuming the conclusion and deducing the hypothesis); and how to use a theorem (verify the hypotheses of the theorem and then appeal to the theorem to get its conclusion).

 

I have given them challenges to find the error in an argument. For example, I asked them to tell me what is wrong with the following argument:

PROBLEM: Solve the equation x/(x - 1) = 1/(x - 1).
 

ARGUMENT: Suppose that x/(x - 1) = 1/(x - 1). Then, by multiplying both sides of this equation by (x - 1) it follows that 

(x/(x _ 1))(x - 1) = (1/(x - 1))(x - 1). That is to say, x = 1. Hence, x = 1 is the solution of the equation x/(x - 1) = 1/(x - 1).

END OF ARGUMENT

 

With such examples the students are taught the fallacy of backwards reasoning. They find such examples to be quite surprising, since they have been taught in pre-college to use this fallacy to solve equations. I myself was taught to use this fallacy in my earlier education. It is quite common to use this fallacy in arguments.

 

Some of the students just continue to stick to their old habits. Others see the point and change their methodology.

 

Sincerely,

Dr. John D. McCarthy

 

 

 

 

 

 

 

 

 

 

 

This is a second response to

This is a second response to BobSpence1:


 

OK, so you were using that

Submitted by BobSpence1 on November 10, 2009 - 3:42pm.

 

I want to add one more thought about the advantage of my direct approach to responding to Samuel.

 

I was right up front about how mathematicians define A^0 and why they define A^0 this way.

 

I didn't try to claim, as some of those who responded to Samuel have apparently claimed, that Samuel had made a mistake in his argument. I think that Samuel actually showed himself to be an astute observer in seeing the circular reasoning that was involved in the proofs which his instructors and others had used in their attempts to prove that A^0 = 1.

 

The only mistake which I have been able to find in Samuel's post is that he never defined what he meant by multiplying A by itself n times when n is equal to 0 (or even what he meant by this when n is equal to 1). (He did indicate what he meant by this when n is an integer greater than 1; namely, that he meant that one takes n factors of A and multiplies them. This is clear from his examples of 3 * 3 * 3 = 3^3 and 3 * 3 = 3^2. Samuel may not have been using correct terminology here, but he made himself clear as to how he was using the terminology.) As I have said in an earlier post, I am willing to grant that Samuel has a definition of multiplying A by itself 0 times which in fact implies that A^0 is equal to 0.

If Samuel were my student and submitted to me a paper containing the gist of his argument, then the first thing that I would do is I would ask him what does he mean by multiplying A by itself 0 times? If he told me something like what he said in his article,  having no A's to multiply we get zero, I would then ask him what makes him think that we get anything by not doing anything to nothing (i.e. having no A's to multiply, not multiplying "them&quotEye-wink. Hopefully, this would get Samuel to examine the intelligibility of his own approach to exponentiation. This would not necessarily lead Samuel to give up on his course of having A^0 to be equal to 0, but at least it would guide him into being self conscious about his own thoughts and the need to make them precise. If I can get a student to just learn this habit of thought, then I think that I have helped that student, even if he chooses to define exponentiation in a different way than mathematicians define it.

 

Of course, as long as the student is in my class and being tested on exponentiation I will require him to interpret any problem involving exponentiation using the mathematician's definition of exponentiation. After all, that is the concept of exponentiation which we talk about in my class, not whatever is Samuel's concept of exponentiation.

I actually think that this approach is treating Samuel with the respect which he deserves for not accepting circular reasoning as a justification for a position.

 

I should add that at least one person who responded to Samuel's argument by showing that Samuel's definition leads to the conclusion that some huge positive number (I don't recall what was this number) is equal to 0, is convinced that he has properly interpreted what Samuel actually said. This person may be correct in his interpretation of Samuel's meaning. I, for one, have not been able to see how to get from what Samuel actually said about exponentiation to a string of equations like:

 

(I) 3 * 3 * 3 = 3 * 3 * 3 * (13)^0 (since there are no factors of 13 in 3 * 3 * 3)

= 3 * 3 * 3 *  (0) (by Samuel's conclusion about 13^0 being 0)

= 0.

 

This is a distillation of the argument which this person gave. The step in the argument which I have not been able to justify from what Samuel actually said is the first step:
 

(I) 3 * 3 * 3 = 3 * 3 * 3 * (13)^0 (since there are no factors of 13 in 3 * 3 * 3)

 

If this step is in fact a logical consequence of what Samuel actually said, then this argument shows that Samuel's argument is fallacious. As I indicated, perhaps this is a correct response to Samuel. I just have not been able to see this step. Perhaps, I am just missing something.


 

Sincerely,

Dr. John D. McCarthy

pedantic

This is another response to BobSpence1:

OK, so you were using that

Submitted by BobSpence1 on November 10, 2009 - 3:42pm.
You write:

"Arguing in such subtle and pedantic ways, especially when there is a much more straightforward way to point out the error, as I showed, is not the way to go."

I looked up the meaning of the word "pedantic" just to make sure that I understood what you were getting at by styling by argumentation as pedantic.
Synonyms: These adjectives mean marked by a narrow, often tiresome focus on or display of learning and especially its trivial aspects: a pedantic writing style; an academic insistence on precision; a bookish vocabulary; donnish refinement of speech; scholastic and excessively subtle reasoning.

I really don't think that my arguments fit this description. I think that they were pretty straightforward. My first argument with Samuel was (i) mathematicians don't prove that a^0 = 1, they define a^0 to be equal to 1 and (ii) there is a good reason for choosing this definition with an extended explanation of what this reason was. I do think that I could be faulted with being too verbose; that is definitely one of my weaknesses. My wife is an excellent writer, much better than I; she gets right to the point in a concise manner without losing any substance to her writing. I wish that I had her gift. The way I write is the way I think. It's hard for me to do any different. But, I recognize that it gets in the way of effective communication.

I do think that your point however has something to say to me. That is that I need to make sure that my students see that there is a good reason for the type of thinking that I try to instill in them; that it isn't just the product of a "tiresome focus on or display of learning and especially its trivial aspects"; or a mere "academic insistence on precision", or "scholastic and excessively subtle reasoning". Perhaps, this impression is coming across to at least some of my students. One of my students this semester spends a good time of just about every class with his head down on the desk, giving me the strong impression that he can't wait until the class is over. Perhaps, that's because he thinks I'm just, as they say, "constipated".

I really don't want to come across this way. For helping me to make a stronger effort towards removing any such impression on my students, I appreciate your warning against being pedantic.

I've tried for instance, to give my students practical examples of where faulty reasoning can lead people.

But, I'm sure there remains room for improvement.

Sincerely,

Dr. John D. McCarthy

 

BobSpence's picture

Dr, John D. McCarthy

Dr, John D. McCarthy wrote:

This is a response to BobSpence1:

 

OK, so you were using that

Submitted by BobSpence1 on November 10, 2009 - 3:42pm.

 

You write:

"I suspect now that the level at which you study math is actually hampering you in addressing errors at this level.  Such a style is simply going to go straight over the head of the mathematically naive, who are precisely the people who will make such errors."

 

Apparently, from what you tell me about your original argument, I missed what you were doing in your original arguments in response to Samuel. Even now, when I go back and read what you actually wrote, I find it very difficult to believe that you were not doing what I thought you were doing. The arguments which you gave at that point are not presented in the form of a  motivation for defining A^0 to be equal to 1. They are presented as an argument that A^0 is equal to 1. 

 

For instance:

"Multiplying any number A by

Submitted by BobSpence1 on November 6, 2009 - 7:42am.

Multiplying any number A by any number B zero times leaves A unchanged:

A  *  (B0) = A 

Therefore (B0) = A/A = 1."

This argument has all the hallmarks of a deduction, not a motivation. The colon indicates an equivalence; what comes before the colon is presented as implying what comes after the colon. It appears as if it is saying:

STATEMENT: Multiplying any number A by any number B zero times leaves A unchanged. That is to say, A  *  (B0) = A.

 

I can believe that this is not what you intended to do; but I think that it is fair to say that it certainly appears that way. If this is not what is being done, then how did you get from what comes before the colon to what comes after the colon?

It is a deduction, and was meant to be a deduction. I don't quite know what you mean by a "motivation" here. It does require acceptance of the idea that "Multiplying any number A by any number B zero times leaves A unchanged", which in ordinary terms is a perfectly comprehensible statement, whatever technical problems you may have with in the strictest formal mathematical terms.

I then showed that this leads to the conclusion that A0 = 1.

I have already conceded that there some sloppiness there, and presented more carefully expressed arguments in subsequent posts.

I was not trying to address Samuel on the details of his argument, just showing that, unless he could find a logical flaw in that STATEMENT, which there isn't, he has to accept that there must be some flaw in his argument. 

The basic 'assumption' in the STATEMENT is that performing some operation zero times is exactly equivalent to not doing it, just another way of saying the same thing.

Quote:

I think that since this is what this argument appears to be saying, that it does not challenge Samuel at all. I am pretty sure that his reaction to this argument would be the same as his reaction to other "proofs" that A^0 = 1 that he was getting from his instructors and other people he went to in order to find out why A^0 = 1. Namely, he would see this argument of yours as circular reasoning. In order to justify what comes after the colon as following from what comes before the colon you have to assume that multiplication of any number A by B^0 is the same thing as "Multiplying any number A by any number B zero times". I'm pretty confident that Samuel would ask himself the same question that he asked himself about the "proofs" which people offered him. Namely, how are you getting the thing which comes after the colon from the thing which comes before the colon. I'm pretty sure that Samuel would say that this is done by assuming that a pattern which holds for positive integers also holds for the integer 0; an assumption which Samuel rightly points out does not have to be valid. This is one of the germs of truth in Samuel's argument; pattern which hold for positive integers don't have to hold for positive integers and 0. He rightly points out that there are patterns which have exceptions. So why shouldn't the pattern that: 

(1) A * (B^3) is the same thing as multiplying A by B three times,
(2) A * (B^2) is the same thing as multiplying A by B two times,
(3) A * (B) is the same thing as multiplying A by B one time,

break down when we get to multiplication of A by B^0? This is actually a very good question that Samuel asks. Indeed, why shouldn't it break down? Why should we expect anything different than that it might break down? Samuel had seen a number of fallacious attempts at showing that A^0 = 1, all of which were based upon an unwarranted assumption that a certain pattern (which Samuel refers to as "the shortcut&quotEye-wink were sustained when we get to the power of zero. Samuel rightly saw that these arguments were circular reasoning.

The pattern actually breaks down at (3), for n = 1, because the the definition of exponentiation in terms of multiplication operations.

Samuel wrote:

 The exponent, the power, the smaller number floating above, is meant to tell you how many times the base number should be multiplied by itself. 

Samuel wrote:

 "To the power" means you multiply the base by itself the number of times shown by the exponent.

Both of which are incorrect on two counts:

1. Exponentiation is only defined in terms of repeated multiplication for the case of positive integers n > 1, not applicable for n <= 1;

2. For such values of n, the number of multiplication operations implied is n - 1, NOT n.

I will also remind you of this

Dr John D. McCarthy wrote:

Now according to the Wikepedia article, A^n is the result of multiplying A repeatedly by A n times. With this definition, it follows that A^0 is the result of multiplying A by A 0 times.

I pointed out then, and I will repeat, that that is not an accurate description of what that Wikipedia article said.

If the Wiki statement was as you describe it, it would indeed lead to that conclusion, but it does not say that. It says explicitly that An is the result of repeated multiplication, and uses diagrams to show that this involves n instances of A, NOT multiplying n times, for n an integer greater than 0. This conflation is at the core of Samuel's error.

Let me repeat: you are making errors, and you have yet to acknowledge this.

Quote:

I don't think that Samuel would have seen your argument as anything different. I think that he would have seen your argument as just another example of circular reasoning; just another example of making an unwarranted assumption about a pattern being sustained.

He would have no justification for such a conclusion, because I did not base my later argument on any thing about patterns - I based it on that STATEMENT above, that performing an operation zero times is equivalent to not performing it, which I still maintain is logically self-evident. Plus the repeated acknowledgement that ultimately it has been decided to define A0 = 1, chosen because it is consistent with various deductive arguments, and fits the pattern. This could be expressed as the definition being chosen to make that pattern consistent, rather than a unjustified extrapolation from the pattern

Quote:


Hence, unlike your evaluation of my response to Samuel, I think that my response to Samuel was much more to the point. I cleared the mathematician of the false charge by Samuel of circular reasoning, by pointing out that mathematicians do not attempt to prove that A^0 = 1; and explicitly offered a motivation for why mathematicians define A^0 to be equal to 1.

 

In my estimation, my answer to Samuel was much more likely to have a chance of persuading Samuel of the benefits of defining A^0 to be equal to 1; while at the same time clearing mathematicians of Samuel's false charges of circular reasoning.

 

I'm sorry. I simply don't agree with your analysis of whose approach to Samuel's post stood a better chance of convincing Samuel that the more desirable course is to define A^0 to be equal to 1.


I agree that had you couched your argument in the form of a motivation rather than in the form of a proof then you would have come across as doing essentially the same thing I was doing; namely, providing a motivation for defining A^0 to be equal to 1. You may not agree with this, but I think that what you actually said comes across as a proof that A^0 is equal to 1, not as a motivation for defining A^0 to be equal to 1.

You write:

 

"Do you address students who are starting with very little math background? Your approach may well work if your students are already at a relatively advanced level."


The lowest level at which I deal with students is at the level of calculus. But some of these students come into my class with poor algebra skills, never mind skills with, say, geometric proofs. (I think that the sort of two-column proofs which I learned as a junior high student have been left out of at least some of these student's pre-college education, if not all of them.)

 

For the last several semesters, I have been teaching first semester freshman calculus. I require the students to justify all of their solutions by giving sound arguments. They are not required to write out detailed arguments, but only to indicate what needs to be done to get a sound argument. Some of my students have told me that this has really helped them to get a hold on the material. Others I think are just bothered by this requirement.

 

So, for the past several semesters, I would not say that I am dealing with students at an advanced level. But I teach them about such things as the direct method of proof of a conditional statement (assume the hypothesis and then deduce the conclusion); the logical fallacy of backwards reasoning (claiming that one has established a conditional statement by assuming the conclusion and deducing the hypothesis); and how to use a theorem (verify the hypotheses of the theorem and then appeal to the theorem to get its conclusion).

 

I have given them challenges to find the error in an argument. For example, I asked them to tell me what is wrong with the following argument:

PROBLEM: Solve the equation x/(x - 1) = 1/(x - 1).
 

ARGUMENT: Suppose that x/(x - 1) = 1/(x - 1). Then, by multiplying both sides of this equation by (x - 1) it follows that 

(x/(x _ 1))(x - 1) = (1/(x - 1))(x - 1). That is to say, x = 1. Hence, x = 1 is the solution of the equation x/(x - 1) = 1/(x - 1).

END OF ARGUMENT

 

With such examples the students are taught the fallacy of backwards reasoning. They find such examples to be quite surprising, since they have been taught in pre-college to use this fallacy to solve equations. I myself was taught to use this fallacy in my earlier education. It is quite common to use this fallacy in arguments.

 

Some of the students just continue to stick to their old habits. Others see the point and change their methodology.

 

Sincerely,

Dr. John D. McCarthy

Curious. I see no "fallacy of backwards reasoning" in that example.

Multiplication of both sides by the same factor is valid, as long as that factor is non-zero. Since it turns out to be zero for the apparent solution, that shows that in this case that solution is not valid.

If you reduce the equation by subtracting both sides by 1/(x - 1), you get  (x - 1)/(x - 1) = 0 which implies that (x - 1), and therefore x, is what we describe in computing as NaN (Not a Number).

 

Favorite oxymorons: Gospel Truth, Rational Supernaturalist, Business Ethics, Christian Morality

"Theology is now little more than a branch of human ignorance. Indeed, it is ignorance with wings." - Sam Harris

The path to Truth lies via careful study of reality, not the dreams of our fallible minds - me

From the sublime to the ridiculous: Science -> Philosophy -> Theology

BobSpence's picture

I think I need to address

I think I need to address this argument in more detail:

Dr John D. McCarthy wrote:

 

Let's follow your definition of multiplying B by A^0, which is multiplying B by A 0 times. 

According to your argument against Samuel, the result of this multiplying of B by A 0 times is B. Indeed, unless this is the result, your argument against Samuel that A^0 is equal to 1, falls to the ground. Your argument requires that multiplying B by A 0 times is equal to B. That's how you are attempting to argue that A^0 is equal to 1. Your reasoning is that since B times 1 is equal to B and multiplying B by A 0 times is equal to B, therefore A^0 is equal to 1. I believe that this is a fair representation of the "gist" of your argument against Samuel.

My argument is based on the basic assumption that performing some operation zero times is exactly equivalent to not doing it, ie just another way of saying the same thing, AND the first IF statement below.

Here is yet another version of my argument:

IF multiplying B by A^0 is equivalent to multiplying B by A 0 times;

AND multiplying B by A 0 times is equivalent to not performing any operation on B, which I maintain is self-evident;

THEN multiplying B by A^0 leaves B unchanged

THEREFORE B x (A^0) = B

Which for non-zero B, dividing both sides by B, leaves us with

(A^0) = 1

I do not start with "since B times 1 is equal to B", that comes at the end.

And I keep acknowledging that the potential hole here is in the first IF statement, which is a reasonable if not mathematically defined extrapolation from the definition that A^n for positive n is a repeated multiplication expression with n factors all equal to A, and the observation that removing a factor in a multiplication is equivalent to replacing it by 1.

Quote:


So, now let's let B be equal to A. Now, we have agreed that multiplying B by A zero times is equal to B. Therefore, it follows, that multiplying B, A, by A 0 times is equal to B, A. 

Now according to the Wikepedia article, A^n is the result of multiplying A repeatedly by A n times. With this definition, it follows that A^0 is the result of multiplying A by A 0 times.

Which is the chief error on your part, as I said in the previous post - that is not what Wiki says. There is no multiplication for any n less than 2. A naive extrapolation of the Wiki definition to n = 0 would be that A^0 is the result of 'multiplying' A by A '-1' times, which could plausibly be interpreted as reverse multiplication, ie division by A, which result is 1.

Quote:

By your observation about the result of multiplying B (in this case, A) by A  0 times, I demonstrated, in the second to last paragraph, that the result of multiplying A by A 0 times is equal to A. 


After all, if it's "good" for any B, then it's "good" for B, when B is equal to A.

Which is based on the assumption that "A^n is the result of multiplying A repeatedly by A n times.", which neither I, nor Wiki, nor you accept as correct.

Quote:

Hence, we have just proven, on the basis of your observation about the effect of multiplying B by A 0 times and the Wikepedia's definition of a6n,  that A^0 is equal to A. 

We have just proved that an invalid definition can lead to an invalid conclusion.

Your continued incorrect assumption about Wikipedia's definition of a^n is troubling, I have pointed this out to you several times now. 



I think that I much prefer the mathematician's definition of A^0 to the Wikepedia article's definition of A^0, with which latter definition you apparently agree.

 

The definition of A^0, in both cases, is simply A^0 = 1.

Are you referring to the justification for that definition? Or did you mean to refer to Wikipedia's definition of A^n? Because you have a persistent misconception of what Wiki's definition of A^n is.

 

 

Favorite oxymorons: Gospel Truth, Rational Supernaturalist, Business Ethics, Christian Morality

"Theology is now little more than a branch of human ignorance. Indeed, it is ignorance with wings." - Sam Harris

The path to Truth lies via careful study of reality, not the dreams of our fallible minds - me

From the sublime to the ridiculous: Science -> Philosophy -> Theology

This is a response to

This is a response to BobSpence1:

 

I think I need to address

Submitted by BobSpence1 on November 11, 2009 - 4:31am.

 

You write:

"My argument is based on the basic assumption that performing some operation zero times is exactly equivalent to not doing it, ie just another way of saying the same thing, AND the first IF statement below."


When you gave your argument you did not have "the first IF statement below. If you had had "the first IF statement below", then it would have been much more clear to me that your argument was intended to be a motivation for defining A^0 = 1 rather than what it appeared to be; namely, a conclusion that A^0 = 1. Again, your use of the term "therefore" in the context of the argument which you actually gave gave the distinct impression that you were arguing that A^0 = 1, not that you were arguing something along the line: "If multiplication B by A^0 has the same result as multiplying B by A zero times, which seems a desirable condition to have satisfied by a reasonable definition of A^0, then the following shows that A^0 = 1. In other words, A^0 = 1 is the only definition of A^0 which has this desirable property." If you had actually presented your argument in this, or a similar form, then I would not have had the distinct impression that you were attempting to prove that A^0 =1 . 

 

Here is yet another version of my argument:

"IF multiplying B by A^0 is equivalent to multiplying B by A 0 times;

AND multiplying B by A 0 times is equivalent to not performing any operation on B, which I maintain is self-evident;

THEN multiplying B by A^0 leaves B unchanged

THEREFORE B x (A^0) = B

Which for non-zero B, dividing both sides by B, leaves us with

(A^0) = 1"

 

I think that to say that this is "yet another version of my argument" is not in accords with what you actually said in your argument. I am quite willing to concede that this is what you intended by your argument, but I think that this is not
"another version" of your argument; unless, all that you mean by "another version" is something like "a variation on a theme". If by "another version" you mean a rephrasing of the argument which you actually gave in an equivalent form, then I would say that this is not an accurate reflection of what you actually said. Again, I am willing to concede that what you actually said was not what you actually intended.

 

You write:

"I do not start with "since B times 1 is equal to B", that comes at the end."

 

I'm not sure what your concern is with this statement. In my mind, it does not matter whether you start with this statement or end with this statement. The use of a previously established statement is a valid step in a proof at any stage of the proof; beginning, middle, or just before the end (when the conclusion is reached). You could have started your proof with the observation: "Note that, as previously established, B times 1 is equal to B.

 

If I mistakenly said that you started with "since B times 1 is equal to B" when you actually did not appeal to this previously established result until later in your argument, then I apologize. But, as I said, I don't think that it makes any difference whether you started with this or did not bring it in until towards the end. Your proof is not compromised in any way relative to the point at which you bring this verity into your argument.

You write:

"And I keep acknowledging that the potential hole here is in the first IF statement, which is a reasonable if not mathematically defined extrapolation from the definition that A^n for positive n is a repeated multiplication expression with n factors all equal to A, and the observation that removing a factor in a multiplication is equivalent to replacing it by 1."

 

Perhaps, this is something that I have simply not been getting. If I have missed your acknowledging of this point, I apologize for not reading your post more careful.


In addition, I don't believe that I have ever claimed that your extrapolations of patterns are not reasonable extrapolations. The only thing that I have been pointing out that is relevant to this issue is that making an extrapolation without pointing out that this extrapolation is being taken as a definition fails to define the thing you are defining by making this extrapolation. The reader of a definition should not be left with having to make the same extrapolation for himself. As I have pointed out in a previous post, any finite pattern extends in infinitely many distinct ways to a larger pattern. This is actually a mathematical theorem. For instance, given any finite sequence, a(1),....,a(n) of n > 0 numbers one can try to find a polynomial p(x) whose values at 1,...,n are a(1),...,a(n). Finding such a polynomial, one could then extrapolate that a(n + 1) = p(n + 1). It is a mathematical theorem that there exist infinitely many such polynomials p(x) all of which satisfy p(i) = a(i) for i = 1,...,n but for which no two of these infinitely many values have the same value at n + 1. Each of these polynomials can be said to give a reasonable extrapolation of the pattern, a(1),...,a(n). This shows that extrapolation does not yield a well-defined definition. If you explicitly state which of the infinitely many extrapolations you are using, then this gives a definition.

 

You write:

"Which is the chief error on your part, as I said in the previous post - that is not what Wiki says. There is no multiplication for any n less than 2. A naive extrapolation of the Wiki definition to n = 0 would be that A^0 is the result of 'multiplying' A by A '-1' times, which could plausibly be interpreted as reverse multiplication, ie division by A, which result is 1."


Again, I don't believe that I have ever claimed that this is not a plausible interpretation of A^{-1}. As I have pointed out, it is in fact what mathematicians take as a definition of A^{-1}. Again, my point has been that until you define A^{-1} by explicitly poiinting out your chosen interpretation you have not defined A^{-1}. Why should the reader be left with having to agree with your "plausible interpretation" in order to know what is your definition of A^{-1}? This becomes especially relevant to the discussion with Samuel, when one of the valid hallmarks of Samuel's argument against mathematicians is that they are assuming that a (plausible) extrapolation of a pattern for positive exponents holds for the "power of zero".

You write:

"and the observation that removing a factor in a multiplication is equivalent to replacing it by 1."


Again, this is an observation which Samuel and everyone else who has spoken in this thread can check when there are at least two factors, a situation in which all contending definitions of A^n agree. But, as Samuel rightly asks, why should this pattern hold when there are no factors (or even only one factor)? Again, until it is explicitly stated that this particular extrapolation is being taken as the basis for a definition for A^0 and the resulting definition is taken, a definition of A^0 has not been given and, consequently, how is anyone able to check assertions about A^0?

 

You write, quoting from one of my posts:

"Quote:


So, now let's let B be equal to A. Now, we have agreed that multiplying B by A zero times is equal to B. Therefore, it follows, that multiplying B, A, by A 0 times is equal to B, A. 

Now according to the Wikepedia article, A^n is the result of multiplying A repeatedly by A n times. With this definition, it follows that A^0 is the result of multiplying A by A 0 times.

Which is the chief error on your part, as I said in the previous post - that is not what Wiki says. There is no multiplication for any n less than 2. A naive extrapolation of the Wiki definition to n = 0 would be that A^0 is the result of 'multiplying' A by A '-1' times, which could plausibly be interpreted as reverse multiplication, ie division by A, which result is 1."

I explicitly acknowledge here and now that the Wiki definition does not speak in terms of "multiplying A by A n times". This has been at best very confusing. My mistake has been in sticking to Samuel's description of "multiplying A by itself n times". By this phrase, for integers greater than 1, Samuel clearly meant nothing different than what the Wiki definition describes: namely, multiplication of n factors of A. I think that this is very clear from Samuel's examples: 3 * 3 * 3 = 3^3 and 3 * 3 = 3^2. I concede that the language: "multiplying A by itself n times" is a misspeak. But I have been willing to use Samuel's language since it was clear to me what Samuel meant (when n is an integer greater than 1). Where I questioned Samuel is in regards to what Samuel means by multiplying A by itself n times when n = 1 or, more relevantly to Samuel's post, when n = 0.

 

I apologize for clouding the discussion by not replacing Samuel's language by more accurate language. I should have been just as precise about Wiki's definition as I was about the mathematician's definition. I meant no disrespect to Wiki.

 

I believe that the only issue which I have taken with Wiki's definition is with regards to exponentiation to the power 1, when it speaks of 3^1 as being the "product" of only one 3 and says that this is evidently 1.

 

You write:

"Which is based on the assumption that "A^n is the result of multiplying A repeatedly by A n times.", which neither I, nor Wiki, nor you accept as correct."

At the risk of repeating myself, I have already acknowledged that I was wasting your time as well as my time by giving an argument that was not relevant to what you had said about exponentiation. As I explained earlier, this was grounded in my guessing that you were willing to work with Samuel's definition (with the understanding of it that I have explained above). I have already apologized for making this presumption.

 

I agree that neither you nor Wiki accept this as correct. I would also agree that it is not correct, but if Samuel had used this phrase instead of his phrase "A^n is the result of multiplying A by itself n times" I would have understood him as meaning the same thing, multiplying n factors of A. Why would I have done this? Because, as I said, I think that he made this clear when he gave his examples: 3 * 3 * 3 = 3^3 and 3 * 3 = 3^2. Again, I would have still asked him, in either phraseology, what he meant by multiplying A by itself n times when n = 1 or n = 0.


Again, I apologize for clouding the discussion by not replacing this inaccurate phraseology by accurate phraseology. It is not been my focus on the particular phraseology that has been used to describe multiplying n factors of A. My focus has been on what does this mean when n =1 or n = 0?

 

You write:

"We have just proved that an invalid definition can lead to an invalid conclusion."


I really don't understand why you keep making this observation. It gives me the distinct impression that you do not believe that anything more is accomplished by showing that an invalid definition leads to an invalid conclusion than showing that an invalid definition can lead to an invalid conclusion (something which, as you have rightly pointed out, we already know). Perhaps, this is not what you are attempting to communicate by this observation, but if this is not your point, then what is your point? 

If this is your point, then I think that you should realize that your point dismissed a major portion of the mathematical industry, an industry which took us to the moon. A major portion of the body of theorems that has been developed by mathematicians relies specifically on making such arguments; arguments which start with an invalid premise and lead to an invalid conclusion.

 

Again, I disagree with your characterization of the alternative definition as being invalid; accept insofar as it is not well-defined; that is, except insofar as it still needs to be made precise.

 

A definition cannot be said to be invalid (accept insofar as it is imprecise or ambiguous). A definition simply tells the listener how the term is being used. If someone explains what is meant by "multiplying A by A n times" in such a way that it agrees with Samuel's definition and even has as a consequence that A^0 = 0, it cannot be said that his definition is invalid. All that can be said about it is that it defines a different concept.

 

You write:

"Your continued incorrect assumption about Wikipedia's definition of a^n is troubling, I have pointed this out to you several times now."
 

Again, I apologize for clouding the discussion by not being careful to state Wikepedia's definition accurately. I should have abandoned phraseology similar to Samuel's phraseology early on. I could have simply said that I understood Samuel's definition
"A^n is the result of multiplying A by itself n times" as meaning "A^n is the result of multiplying n factors of A". This is indeed how I understood Samuel, for reasons which I have explained above. But, by continuing to use this phraseology, I definitely was confusing. For this, I apologize. I was trying not to be picky about the words that were being used. I only was interested in having a definition which was unambiguous. I believe that Samuel removed the inaccuracy of his language for the case where n is an integer greater than 1 by his examples: 3 * 3 * 3 = 3^3 and 3 * 3 = 3^2. I don't believe that he removed the ambiguity in his definition for the case where n = 1 or n = 0.

 

You write:


"I think that I much prefer the mathematician's definition of A^0 to the Wikepedia article's definition of A^0, with which latter definition you apparently agree."


I'm a bit confused by this last sentence. Is this a quote from me? It was not written out in your post, like the other quotes from me, as a quote from me. At the risk of confusing things, I'm going to assume that it is a quote from me.


I have already apologized (I think more than once) for failing to take notice of Wikepedia's care in defining x^0. I'm not sure what else I can do to rectify this failure.

 

You write:

"The definition of A^0, in both cases, is simply A^0 = 1.

Are you referring to the justification for that definition? Or did you mean to refer to Wikipedia's definition of A^n? Because you have a persistent misconception of what Wiki's definition of A^n is."

 

I have already apologized (I think more than once) for failing to take notice of Wikepedia's care in defining x^0. I'm not sure what else I can do to rectify this failure.

 

I hope that this has cleared up to some extent what has transpired in this thread.


Sincerely,


Dr. John D. McCarthy

 

 

 

 

 

 

 

 

 



"Suppose

 

BobSpence's picture

Looking back, I would say I

 

Looking back, I would say I have presented two basic arguments against Samuel's post.

The first one was based on the proposition that 

"Removing a factor in a chain of multiplications is equivalent to replacing it with unity"'

which directly addressed a key part of his argument, where he ultimately assumed that an empty expression is equivalent to 0, which is simply not true - it is totally undefined.

Using such an assumption, the argument can be taken all the way down to zero A's , if you start with an expression with 2 or more A's - you never have to deal with an empty expression or one with just one factor.

If we assume that a chain of multiplication with n factors = A and m factors = 1, where  m+ n >= 2 (so we always have at least one multiplication operation)

is equivalent to A^n, which does admittedly go beyond the basic positive integer definition of A^n,

but does allow us to derive a value for A^0.

Expressed that way, it is NOT based on a pattern observation, and avoids having to make any assumptions about an expression with only one factor.

I would say it is up to you to point out what are the clear problems with my assumptions, which I see as prima facie quite logical, and reasonable, which I feel is all that is necessary to show Samuel his error.

=================

You said above that 

Quote:

I believe that the only issue which I have taken with Wiki's definition is with regards to exponentiation to the power 1, when it speaks of 3^1 as being the "product" of only one 3 and says that this is evidently 1.

What Wiki actually said is

Wikipedia wrote:

Notice that 3is the"product" of only one 3, which is defined to be 3.

(my highlighting and underlining)

Was that a simple typo in your statement or did you read the value "1" somewhere else in the Wikipedia article?

===============================

 

I then presented the second argument based on the assumption that performing some operation zero times is exactly equivalent to not doing it.

When I said "version" I was referring to the progressive refinement I made to minimize jumps in logic and hidden assumptions.

===============================

 

When I said that '"We have just proved that an invalid definition can lead to an invalid conclusion." 

I do realize that useful arguments can be based on assuming an invalid proposition, but typically based on the argument leading to a clear contradiction, the standard "Reductio ad Absurdum".

However, your argument just lead to "A^0 = A", which was the result in dispute, NOT an explicit basic contradiction, such as "1 = 0", so it really does not serve any useful point  in this context.

==============================

Quote:

"I think that I much prefer the mathematician's definition of A^0 to the Wikepedia article's definition of A^0, with which latter definition you apparently agree."

I'm a bit confused by this last sentence. Is this a quote from me? It was not written out in your post, like the other quotes from me, as a quote from me. At the risk of confusing things, I'm going to assume that it is a quote from me. 

It is a direct copy/paste from one of your posts about half way down the first page of this thread.

 

I hope this further clarifies things.

 

 

Favorite oxymorons: Gospel Truth, Rational Supernaturalist, Business Ethics, Christian Morality

"Theology is now little more than a branch of human ignorance. Indeed, it is ignorance with wings." - Sam Harris

The path to Truth lies via careful study of reality, not the dreams of our fallible minds - me

From the sublime to the ridiculous: Science -> Philosophy -> Theology

This is a response to

This is a response to BobSpence1: 

Looking back, I would say I

Submitted by BobSpence1 on November 11, 2009 - 5:15pm.

 

 

You write, concerning one of the arguments which you gave in response to Samuel's post:

"The first one was based on the proposition that 

"Removing a factor in a chain of multiplications is equivalent to replacing it with unity"'

which directly addressed a key part of his argument, where he ultimately assumed that an empty expression is equivalent to 0, which is simply not true - it is totally undefined." 


I agree totally with your assessment of Samuel's assumption. This is what prompted me to ask the question as to why one would assume that one got anything from doing nothing to nothing. 

 

Since you are talking at this point in your post about your first argument, I assume that you are, at this point in your post, discussing the following argument:

"If we look at the sequence

Submitted by BobSpence1 on October 13, 2008 - 6:39pm.

 

If we look at the sequence of expressions, the 'problem' arises because you omitted the implied '1' in the 0 case.  Removing a factor in a chain of multiplications is NOT equivalent to replacing it with zero, it is equivalent to replacing it with unity. Replacement by zero would apply to removing an element in a chain of additions.

3 ^ 3 = 3 X 3 X 3

3 ^ 2= 1 X 3 X 3

3 ^ 1 = 1 X 1 X 3

3 ^ 0 = 1 X 1 X 1

3  ^ (-1) = 1 x 1 X 3^(-1)

3 ^ (-2) = 1 X 3^(-1) X 3^(-1)" 

You write: 

"Using such an assumption, the argument can be taken all the way down to zero A's , if you start with an expression with 2 or more A's - you never have to deal with an empty expression or one with just one factor.

If we assume that a chain of multiplication with n factors = A and m factors = 1, where  m+ n >= 2 (so we always have at least one multiplication operation)

is equivalent to A^n, which does admittedly go beyond the basic positive integer definition of A^n,

but does allow us to derive a value for A^0.

Expressed that way, it is NOT based on a pattern observation, and avoids having to make any assumptions about an expression with only one factor." 

 

This is confusing me. This looks like it is related to your second argument: 

"Multiplying any number A by

Submitted by BobSpence1 on November 6, 2009 - 7:42am.

 

Multiplying any number A by any number B zero times leaves A unchanged:

A  *  (B0) = A 

Therefore (B0) = A/A = 1

Whereas Adding B to A zero times leaves B unchanged:

A + (B * 0) = A

Therefore (B * 0) = A - A  = 0"

 

Even then, I am confused, since in this second argument you multiplied by B^n, with n = 0, not by A^n. 

 

At the risk of wasting both of our time, I will try to address your question as best as I can, not fully understanding to what argument of yours you are referring. 

 

Do you mean to say m > = 1 and n > = 1 or just that m + n > = 2?

 

At the risk of wasting both of our time, I'm going to assume that you only meant that m + n > = 2. (After all, this would, as you indicate, leave us with having at least one multiplication operation). 

I think that everyone, including Samuel, is using some definition of A^n which can be easily verified to have the property that (A^n)(1^m) = A^n provided n and m are both positive integers.

Assuming, as everyone is assuming, that A^0 is a number, this equation also holds when n = 0 and m > = 2. 


I don't see how you are getting this equation, (A^n)(1^m) = A^n, to hold when n > = 2 and m = 0, without assuming that multiplication by 1^0 is the same thing as multiplying A by 1 zero times (i.e. not executing the operation of multiplication by 1), or assuming that 1^0 = 1 (i.e. without assuming one of the other of these two assumptions). 

 

I don't think that my analysis of your argument requires you to be working with an expression with only one factor. You can repeat your second argument with (A * A) * (B^0) = (A * A) instead of A * (B^0) = A, so that you have at least one multiplication operation; namely A * A.  I still have the same question. How would you be getting that (A * A) * B^0 =

(A * A) without assuming something about the pattern (A * A) * (B^3) = (A * A) * (B * B * B) = ((((A * A) * B) * B) * B), the result of multiplying A * A by B three times, etc., etc.   

I'm sorry if I'm being slow, but I don't see how this is obtained without making some assumption about multiplication by B^0. Perhaps, whatever is your assumption it is not based upon a pattern. If not, then what is it based upon? 

 

Likewise, regarding your first argument, 

"3 ^ 3 = 3 X 3 X 3

3 ^ 2= 1 X 3 X 3

3 ^ 1 = 1 X 1 X 3

3 ^ 0 = 1 X 1 X 1"

you could write:

"(A * A) * (3^3) = ((((A * A) * 3) * 3) * 3), etc."

so that you would always have at least one multiplication. But, I would still have the same question. How would you get to the step: 

STEP: (A * A) * (3^0) = ((((A * A) * 1) * 1) * 1)?

This STEP appears to be relying on the continuance of a pattern. Perhaps, you are relying upon something else. If so, upon what are you relying? 

 

You write: 

"I then presented the second argument based on the assumption that performing some operation zero times is exactly equivalent to not doing it.

When I said "version" I was referring to the progressive refinement I made to minimize jumps in logic and hidden assumptions." 

Thank you for this explanation; in that sense, your later argument is a version of the original argument. 

 

You write:

"When I said that '"We have just proved that an invalid definition can lead to an invalid conclusion." 

I do realize that useful arguments can be based on assuming an invalid proposition, but typically based on the argument leading to a clear contradiction, the standard "Reductio ad Absurdum".

However, your argument just lead to "A^0 = A", which was the result in dispute, NOT an explicit basic contradiction, such as "1 = 0", so it really does not serve any useful point  in this context."

 

I agree that my argument has not lead to an absurdity. You are correct about this.

However, I still think that it serves a "useful point in this context". At the very least it demonstrates that two usages of the phrase "multiply A by itself n times" and "multiply A by A (i.e. itself) n times" one of which is Samuel's usage (i.e A^n is the result of multiplying A by itself n times, in which Samuel apparently means, on the basis of his explicit examples, to take n factors of A and multiply them) and another usage of this phrase which means to start with A and multiply A by A repeatedly n times (i.e. take (n + 1) factors of A and multiply them), if taken without explicitly distinguishing each of the meanings of this phrase, leads to something that even Samuel doesn't want; namely that A^0 = A. If, at the very least, this could cause Samuel to define what he means by multiplying A by itself n times and, more importantly, what he means by multiplying A by itself n times when n = 1 or n = 0, this would represent some progress in the discussion.

 

You write: 
 

"Quote:

 

"I think that I much prefer the mathematician's definition of A^0 to the Wikepedia article's definition of A^0, with which latter definition you apparently agree."

I'm a bit confused by this last sentence. Is this a quote from me? It was not written out in your post, like the other quotes from me, as a quote from me. At the risk of confusing things, I'm going to assume that it is a quote from me. 

 

 

It is a direct copy/paste from one of your posts about half way down the first page of this thread."


Fair enough. I can only hope that I wrote this before I confessed my fault in not observing Wikepedia's care in defining x^0. If I wrote this after this point, then I cannot explain why. I did at one point become aware of Wikepedia's care in defining x^0, and I tried not to repeat my failure in observing this. 

 

 

 

 

You write:

 

"You said above that 

 

Quote:

 

I believe that the only issue which I have taken with Wiki's definition is with regards to exponentiation to the power 1, when it speaks of 3^1 as being the "product" of only one 3 and says that this is evidently 1.

 

 

What Wiki actually said is

 

Wikipedia wrote:

 

Notice that 3is the"product" of only one 3, which is defined to be 3.

 

 

(my highlighting and underlining)

Was that a simple typo in your statement or did you read the value "1" somewhere else in the Wikipedia article?"Wikipedia wrote:

 

 

What I found in an earlier post is:

 

"Wikipedia wrote:

Notice that 31 is the product of only one 3, which is evidently 3." 

 

By "highlighting" are you referring, in particular, to the quotation marks around "product"? Apparently, these quotation marks do not appear in the original Wikepedia article. 

 

Thank you for catching this. Yes, it was a simple typo. I had no intention of accusing Wikepedia of making such a blatantly obvious departure from the standard definition of exponentiation. It was never my impression that Wikepedia was attempting to give a different definition of exponentiation than the standard one. I only questioned whether Wikepedia had made this definition explicit (such as, for example, with reference to this "product" issue). 
 

My wife asked me the following question. Has Samuel paid any attention to any of this? 

 

I only now noticed that Samuel's article was posted in 2007. Perhaps, I have not been helping Samuel at all. There's no sign of his presence, other than his blog on logical fallacies. 

 

Sincerely,


Dr. John D. McCarthy  



 

 

 

 

 

This is a further response

This is a further response to BobSpence1:

 

Looking back, I would say I

Submitted by BobSpence1 on November 11, 2009 - 5:15pm.

 

You write:

"Expressed that way, it is NOT based on a pattern observation, and avoids having to make any assumptions about an expression with only one factor."

 

Perhaps, I am making too much of what you say here, but it appears that you are making a claim that you have given a motivation for defining A^0 to be equal to 1 which is "NOT based on a pattern observation".

 

 

If you have actually done this, then this is, as far as I know, quite novel.


You will note that not even the Wikepedia article, which you seem to find one of the most dependable sources of information regarding exponentiation, claims to do this. The Wikepedia's article is pretty explicit about assuming that the pattern:
"A^{n - m} = A^n/(A^m)", which is fairly easily established (by induction) for the situation where m, n, and n - m are all integers greater than 1, holds when m is an integer greater than 1 and n = m.

 

Frankly, I know of no one besides yourself who has claimed to give a motivation for defining A^0 to be equal to 1 which motivation does not rely on some presumed pattern. Of course, even if no one besides yourself has claimed to do this, that does not imply that you have not done this.

 

But it does make me want to put your argument under very careful scrutiny.

 

I have asked you a question about this argument in my previous post. I look forward to your response.


Sincerely,

Dr. John D. McCarthy 

 

BobSpence's picture

Dr. John D. McCarthy

Dr. John D. McCarthy wrote:

This is a response to BobSpence1: 

Looking back, I would say I

 

Submitted by BobSpence1 on November 11, 2009 - 5:15pm.

 

 

You write, concerning one of the arguments which you gave in response to Samuel's post:

"The first one was based on the proposition that 

"Removing a factor in a chain of multiplications is equivalent to replacing it with unity"'

which directly addressed a key part of his argument, where he ultimately assumed that an empty expression is equivalent to 0, which is simply not true - it is totally undefined." 


I agree totally with your assessment of Samuel's assumption. This is what prompted me to ask the question as to why one would assume that one got anything from doing nothing to nothing. 

I never made any arguments where I assumed anything about "doing nothing to nothing. "

The above argument was the initial one, based on the proposition I stated there, that "Removing a factor in a chain of multiplications is equivalent to replacing it with unity".

It did not involve the other proposition I used in my second approach, that "multiplying by 1 is equivalent to doing nothing".

 

Since you are talking at this point in your post about your first argument, I assume that you are, at this point in your post, discussing the following argument:
 

"If we look at the sequence

Submitted by BobSpence1 on October 13, 2008 - 6:39pm.

 

If we look at the sequence of expressions, the 'problem' arises because you omitted the implied '1' in the 0 case.  Removing a factor in a chain of multiplications is NOT equivalent to replacing it with zero, it is equivalent to replacing it with unity. Replacement by zero would apply to removing an element in a chain of additions.

3 ^ 3 = 3 X 3 X 3

3 ^ 2= 1 X 3 X 3

3 ^ 1 = 1 X 1 X 3

3 ^ 0 = 1 X 1 X 1

3  ^ (-1) = 1 x 1 X 3^(-1)

3 ^ (-2) = 1 X 3^(-1) X 3^(-1)" 

I then developed that line of reasoning to the one you refer to in the following:

Dr. John D. McCarthy wrote:

 

You write: 

 

 

"Using such an assumption, the argument can be taken all the way down to zero A's , if you start with an expression with 2 or more A's - you never have to deal with an empty expression or one with just one factor.

If we assume that a chain of multiplication with n factors = A and m factors = 1, where  m+ n >= 2 (so we always have at least one multiplication operation)

is equivalent to A^n, which does admittedly go beyond the basic positive integer definition of A^n,

but does allow us to derive a value for A^0.

Expressed that way, it is NOT based on a pattern observation, and avoids having to make any assumptions about an expression with only one factor." 

This is confusing me. This looks like it is related to your second argument: 
 

"Multiplying any number A by

Submitted by BobSpence1 on November 6, 2009 - 7:42am.

 

Multiplying any number A by any number B zero times leaves A unchanged:

A  *  (B0) = A 

Therefore (B0) = A/A = 1

Whereas Adding B to A zero times leaves B unchanged:

A + (B * 0) = A

Therefore (B * 0) = A - A  = 0"

 

Even then, I am confused, since in this second argument you multiplied by B^n, with n = 0, not by A^n. 

Are you serious that you are confused by my accidentally swapping the roles of A and B?

That aside, the first argument is NOT explicitly related to my 2nd. It is a separate approach, as I have described in detail.

Dr. John D. McCarthy wrote:

At the risk of wasting both of our time, I will try to address your question as best as I can, not fully understanding to what argument of yours you are referring. 

 

Do you mean to say m > = 1 and n > = 1 or just that m + n > = 2?

 

At the risk of wasting both of our time, I'm going to assume that you only meant that m + n > = 2. (After all, this would, as you indicate, leave us with having at least one multiplication operation). 

I meant what I said, that m + n > = 2, for just the reason you refer to above. I could have added m >= 0, n >= 0, but I just relied on the assumption that in ordinary terms, when referring to a chain of multiplied factors, that "-1" occurrences of any particular factor doesn't quite make sense. 0 or greater occurrences of a particular factor in the chain is perfectly understandable by mere mortals. A bit sloppy, sorry, but really no ambiguity.

Dr. John D. McCarthy wrote:

I think that everyone, including Samuel, is using some definition of A^n which can be easily verified to have the property that (A^n)(1^m) = A^n provided n and m are both positive integers.

Assuming, as everyone is assuming, that A^0 is a number, this equation also holds when n = 0 and m > = 2. 


I don't see how you are getting this equation, (A^n)(1^m) = A^n, to hold when n > = 2 and m = 0, without assuming that multiplication by 1^0 is the same thing as multiplying A by 1 zero times (i.e. not executing the operation of multiplication by 1), or assuming that 1^0 = 1 (i.e. without assuming one of the other of these two assumptions). 

I repeatedly clarified that I was indeed making the assumption that multiplication by B^0 is the same thing as multiplying A by B zero times, for any non-zero value of  B, not just 1.

Dr. John D. McCarthy wrote:

I don't think that my analysis of your argument requires you to be working with an expression with only one factor. You can repeat your second argument with (A * A) * (B^0) = (A * A) instead of A * (B^0) = A, so that you have at least one multiplication operation; namely A * A.  I still have the same question. How would you be getting that (A * A) * B^0 =

(A * A) without assuming something about the pattern (A * A) * (B^3) = (A * A) * (B * B * B) = ((((A * A) * B) * B) * B), the result of multiplying A * A by B three times, etc., etc.   

I'm sorry if I'm being slow, but I don't see how this is obtained without making some assumption about multiplication by B^0. Perhaps, whatever is your assumption it is not based upon a pattern. If not, then what is it based upon? 

According to my first argument, I would start with A * A * B * B =  A * (B * B) = A * A * (B2)

I would then replace both B's on the LHS by 1, and decrement the exponent of B on the RHS by 2, in accord with the key assumptions of my 1st approach, that replacing a factor in a multiplication by 1 is equivalent to deleting the factor from the chain, and that the exponent is a count of the number of factors of that value being grouped together under the exponentiation expression.

A * A * 1 * 1 = A * A * (B0)

which clearly is reducible to

1 * 1 = (B0),

or B0 = 1;

I recognise some definitional problems with this, but it is not really based on any inference from patterns with greater that 2 occurrences of A or B.

Dr. John D. McCarthy wrote:

Likewise, regarding your first argument, 

 

"3 ^ 3 = 3 X 3 X 3

3 ^ 2= 1 X 3 X 3

3 ^ 1 = 1 X 1 X 3

3 ^ 0 = 1 X 1 X 1"

you could write:

"(A * A) * (3^3) = ((((A * A) * 3) * 3) * 3), etc."

so that you would always have at least one multiplication. But, I would still have the same question. How would you get to the step: 

STEP: (A * A) * (3^0) = ((((A * A) * 1) * 1) * 1)?

This STEP appears to be relying on the continuance of a pattern. Perhaps, you are relying upon something else. If so, upon what are you relying? 

I wouldn't. I just described my approach in this first argument in the text above.

Now to concentrate on my second argument:

Dr. John D. McCarthy wrote:

You write: 

"I then presented the second argument based on the assumption that performing some operation zero times is exactly equivalent to not doing it.

When I said "version" I was referring to the progressive refinement I made to minimize jumps in logic and hidden assumptions." 

Thank you for this explanation; in that sense, your later argument is a version of the original argument. 

 

You write:

"When I said that '"We have just proved that an invalid definition can lead to an invalid conclusion." 

I do realize that useful arguments can be based on assuming an invalid proposition, but typically based on the argument leading to a clear contradiction, the standard "Reductio ad Absurdum".

However, your argument just lead to "A^0 = A", which was the result in dispute, NOT an explicit basic contradiction, such as "1 = 0", so it really does not serve any useful point  in this context."

 

I agree that my argument has not lead to an absurdity. You are correct about this.

However, I still think that it serves a "useful point in this context". At the very least it demonstrates that two usages of the phrase "multiply A by itself n times" and "multiply A by A (i.e. itself) n times" one of which is Samuel's usage (i.e A^n is the result of multiplying A by itself n times, in which Samuel apparently means, on the basis of his explicit examples, to take n factors of A and multiply them) and another usage of this phrase which means to start with A and multiply A by A repeatedly n times (i.e. take (n + 1) factors of A and multiply them), if taken without explicitly distinguishing each of the meanings of this phrase, leads to something that even Samuel doesn't want; namely that A^0 = A. If, at the very least, this could cause Samuel to define what he means by multiplying A by itself n times and, more importantly, what he means by multiplying A by itself n times when n = 1 or n = 0, this would represent some progress in the discussion.

[ I agree with your analysis of Samuel's error, but I still don't see your presentation of that argument as being the best way of demonstrating his error to him.

Dr. John D. McCarthy wrote:

You write: 
 

"Quote:

 

"I think that I much prefer the mathematician's definition of A^0 to the Wikepedia article's definition of A^0, with which latter definition you apparently agree."

I'm a bit confused by this last sentence. Is this a quote from me? It was not written out in your post, like the other quotes from me, as a quote from me. At the risk of confusing things, I'm going to assume that it is a quote from me. 

 

 

It is a direct copy/paste from one of your posts about half way down the first page of this thread."


Fair enough. I can only hope that I wrote this before I confessed my fault in not observing Wikepedia's care in defining x^0. If I wrote this after this point, then I cannot explain why. I did at one point become aware of Wikepedia's care in defining x^0, and I tried not to repeat my failure in observing this. 

 

 

You write:

 

"You said above that 

 

Quote:

 

I believe that the only issue which I have taken with Wiki's definition is with regards to exponentiation to the power 1, when it speaks of 3^1 as being the "product" of only one 3 and says that this is evidently 1.

 

 

What Wiki actually said is

 

Wikipedia wrote:

 

Notice that 3is the"product" of only one 3, which is defined to be 3.

 

 

(my highlighting and underlining)

Was that a simple typo in your statement or did you read the value "1" somewhere else in the Wikipedia article?"Wikipedia wrote:

 

 

What I found in an earlier post is:

 

"Wikipedia wrote:

Notice that 31 is the product of only one 3, which is evidently 3." 

 

By "highlighting" are you referring, in particular, to the quotation marks around "product"? Apparently, these quotation marks do not appear in the original Wikepedia article. 

That quote from Wikipedia still appears in my browser exactly as I quoted, with the quotes around the word product. I added the underlining, and the bolding of the digit '3' for emphasis.

Dr. John D. McCarthy wrote:

Thank you for catching this. Yes, it was a simple typo. I had no intention of accusing Wikepedia of making such a blatantly obvious departure from the standard definition of exponentiation. It was never my impression that Wikepedia was attempting to give a different definition of exponentiation than the standard one. I only questioned whether Wikepedia had made this definition explicit (such as, for example, with reference to this "product" issue). 
 

My wife asked me the following question. Has Samuel paid any attention to any of this? 

 

I only now noticed that Samuel's article was posted in 2007. Perhaps, I have not been helping Samuel at all. There's no sign of his presence, other than his blog on logical fallacies. 

Sincerely,


Dr. John D. McCarthy  

I strongly suspect that is the case. 

I have found this discussion of interest, in refining my skills and understanding of the subject, as well as (hopefully) refining the clarity with which I convey my personal insights.

Favorite oxymorons: Gospel Truth, Rational Supernaturalist, Business Ethics, Christian Morality

"Theology is now little more than a branch of human ignorance. Indeed, it is ignorance with wings." - Sam Harris

The path to Truth lies via careful study of reality, not the dreams of our fallible minds - me

From the sublime to the ridiculous: Science -> Philosophy -> Theology

This is a response to: Dr.

This is a response to:

Dr. John D. McCarthy
Submitted by BobSpence1 on November 12, 2009 - 7:08am.


You quote from one of my previous posts:

"You write, concerning one of the arguments which you gave in response to Samuel's post:

"The first one was based on the proposition that

"Removing a factor in a chain of multiplications is equivalent to replacing it with unity"'

which directly addressed a key part of his argument, where he ultimately assumed that an empty expression is equivalent to 0, which is simply not true - it is totally undefined."


I agree totally with your assessment of Samuel's assumption. This is what prompted me to ask the question as to why one would assume that one got anything from doing nothing to nothing."

And then you write:

"I never made any arguments where I assumed anything about "doing nothing to nothing. ""


When I spoke about asking "the question as why one would assume that one got anything from doing nothing to nothing" I was referring to my response to Samuel. I would have hoped that this was clear from my saying that "I agree totally with your assessment of Samuel's assumption." Samuel had said, concerning A^0 (or maybe it was just 3^0), something like "having nothing to multiply to we get 0". At this point, Samuel was talking about having no A's (3's?) (and nothing else). So Samuel was talking about having nothing (no A's and nothing else) and not multiplying (and, hence, doing nothing). Samuel then concluded that he got zero. So I asked him why he would assume that one got anything from doing nothing to nothing.


My comment about "doing nothing to nothing" was not addressing your first argument. Rather it was addressing your
statement about Samuel's argument: "where he ultimately assumed that an empty expression is equivalent to 0, which is simply not true - it is totally undefined."


My comment about "doing nothing to nothing" was addressing your point that "it is totally undefined". The "it" that "is totally undefined", I understood to be the "it" that Samuel apparently thinks that you get when you take nothing (i.e. no factors) and do nothing to it (i.e.don't multiply).


I hope that this makes it clear to what I was referring when I spoke of "doing nothing to nothing".

 

You write:

 

"Are you serious that you are confused by my accidentally swapping the roles of A and B?"

 

If I had realized that you had accidentally swapped the roles of A and B, then I might have been able to come to the conclusion about which argument you were referring to, the first one or the second one. My confusion was over not being able to decide to which argument you were referring. I thought that perhaps I had missed something. 

 

You write:

"I meant what I said, that m + n > = 2, for just the reason you refer to above. I could have added m >= 0, n >= 0, but I just relied on the assumption that in ordinary terms, when referring to a chain of multiplied factors, that "-1" occurrences of any particular factor doesn't quite make sense. 0 or greater occurrences of a particular factor in the chain is perfectly understandable by mere mortals. A bit sloppy, sorry, but really no ambiguity."

I didn't assume that you were allowing m or n to be negative. I assumed that you were talking about m >= 0 and n >= 0.

I just wanted to make sure that you were not requiring m >= 1 and n >= 1. I guess that if you had been doing that you probably wouldn't have bothered to say m + n >=2.

 

You write:

"I repeatedly clarified that I was indeed making the assumption that multiplication by B^0 is the same thing as multiplying A by B zero times, for any non-zero value of  B, not just 1."

 

In my mind, this confirms what I was saying about your argument relying upon a pattern. In this case, the pattern of which I speak is this pattern:

(i) A * (B^3) = A * (B * B * B) = (((A * B) * B) * B) so that multiplication of A by B^3 is the same thing as multiplying A by B three times

(ii) A * (B^2) = A * (B * B) = ((A * B) * B) so that multiplication of A by B^2 is the same thing as multiplying A by B two times

(iii) A * (B^1) = A * B so that multiplication of A by B^1 is the same thing as multiplying A by B one time

Now the assumption that multiplication by B^0 is the same thing as multiplying A by B zero times is, in my mind, the assumption that the pattern in (i) through (iii), where n = 3, 2, and 1, continues to hold when n = 0. I agree that you never appealed to this pattern. Nevertheless, I think that your assumption amounts to the assumption that this pattern still holds when n = 0.

 

You write:

"According to my first argument, I would start with A * A * B * B =  A * (B * B) = A * A * (B2)

I would then replace both B's on the LHS by 1, and decrement the exponent of B on the RHS by 2, in accord with the key assumptions of my 1st approach, that replacing a factor in a multiplication by 1 is equivalent to deleting the factor from the chain, and that the exponent is a count of the number of factors of that value being grouped together under the exponentiation expression.

A * A * 1 * 1 = A * A * (B0)

which clearly is reducible to

1 * 1 = (B0),

or B0 = 1;

I recognise some definitional problems with this, but it is not really based on any inference from patterns with greater that 2 occurrences of A or B."


In this case, the pattern which I see you using is expressed in your words, "replacing a factor in a multiplication by 1 is equivalent to deleting the factor from the chain, and that the exponent is a count of the number of factors of that value being grouped together under the exponentiation expression". The statement contained in these words can be verified when the number p of a given factor, say B, is at least 2, before you proceed to replace one of the factors of B by 1, (even with Samuel's definition (as clarified by his explicit examples)).

Assuming that these words still hold when p = 1 is, in my mind, assuming that a previously established pattern for p >=2 still holds when p = 1. 

 

I hope that this helps to clarify where I see you assuming that certain observable patterns still hold when, for example, n = 0.

 

You write:

 

Dr. John D. McCarthy wrote:

Likewise, regarding your first argument, 

 

"3 ^ 3 = 3 X 3 X 3

3 ^ 2= 1 X 3 X 3

3 ^ 1 = 1 X 1 X 3

3 ^ 0 = 1 X 1 X 1"

you could write:

"(A * A) * (3^3) = ((((A * A) * 3) * 3) * 3), etc."

so that you would always have at least one multiplication. But, I would still have the same question. How would you get to the step: 

STEP: (A * A) * (3^0) = ((((A * A) * 1) * 1) * 1)?

This STEP appears to be relying on the continuance of a pattern. Perhaps, you are relying upon something else. If so, upon what are you relying? 

I wouldn't. I just described my approach in this first argument in the text above."

Call me slow, but I don't understand what you mean by "I wouldn't." in response to my question, "If so, upon what are you relying?"

Are you saying that you are not relying on anything? If you are not relying on anything, then how are you predicating anything? I'm confused.

 

You write:

"That quote from Wikipedia still appears in my browser exactly as I quoted, with the quotes around the word product. I added the underlining, and the bolding of the digit '3' for emphasis."

 

I can't explain why your browser is different from mine but what follows is a direct cut and paste from my browser:

"

Exponentiation of A by zero is defined as corresponding to no operation at all, making it consistent with both above definitions, ie, neither multiplication or division is actually involved.

Wikipedia wrote:

Notice that 31 is the product of only one 3, which is evidently 3.

Also note that 35 = 3·34. Also 34 = 3·33. Continuing this trend, we should have

31 = 3·30.

Another way of saying this is that when n, m, and n − m are positive (and if x is not equal to zero), one can see by counting the number of occurrences of x that

 \frac{x^n}{x^m} = x^{n - m}.

Extended to the case that n and m are equal, the equation would read

 1 = \frac{x^n}{x^n} = x^{n - n} = x^0

since both the numerator and the denominator are equal. Therefore we take this as the definition of x0.

Therefore we define 30 = 1 so that the above equality holds. This leads to the following rule:

> Any number to the power 1 is itself.

> Any nonzero number to the power 0 is 1; one interpretation of these powers is as empty products.

 

IOW, the definitions for the cases where n = 1, 0, and negative, (and non-integer, of course), are chosen so as to be as mathematically consistent as possible with the basic definition for non-zero exponents greater than 1."

 

Is this what my department's computer technician would call "computer voodoo"? 


Sincerely,

Dr. John D. McCarthy

 

 

 

 

 

BobSpence's picture

Dr. John D. McCarthy

Dr. John D. McCarthy wrote:

 

You write:

 

Dr. John D. McCarthy wrote:

Likewise, regarding your first argument, 

 

"3 ^ 3 = 3 X 3 X 3

3 ^ 2= 1 X 3 X 3

3 ^ 1 = 1 X 1 X 3

3 ^ 0 = 1 X 1 X 1"

you could write:

"(A * A) * (3^3) = ((((A * A) * 3) * 3) * 3), etc."

so that you would always have at least one multiplication. But, I would still have the same question. How would you get to the step

STEP: (A * A) * (3^0) = ((((A * A) * 1) * 1) * 1)?

This STEP appears to be relying on the continuance of a pattern. Perhaps, you are relying upon something else. If so, upon what are you relying? 

I wouldn't. I just described my approach in this first argument in the text above."

Call me slow, but I don't understand what you mean by "I wouldn't." in response to my question, "If so, upon what are you relying?"

Are you saying that you are not relying on anything? If you are not relying on anything, then how are you predicating anything? I'm confused.

I was responding to your question contained in my quote from your post, starting at the words "How would you get to the step:" - underlined, hope it shows up in your browser.

The argument I was referring to was immediately above that section of text; I will re-post it here:

Quote:

 

According to my first argument, I would start with A * A * B * B =  A * (B * B) = A * A * (B2)

I would then replace both B's on the LHS by 1, and decrement the exponent of B on the RHS by 2, in accord with the key assumptions of my 1st approach, that replacing a factor in a multiplication by 1 is equivalent to deleting the factor from the chain, and that the exponent is a count of the number of factors of that value being grouped together under the exponentiation expression.

A * A * 1 * 1 = A * A * (B0)

which clearly is reducible to

1 * 1 = (B0),

or B0 = 1;

 

Regarding 'patterns' - it is arguable that the patterns were at least suggestive of the conclusion, but my argument did not logically rely on extrapolating from the pattern, only from the first member of the sequence.

Favorite oxymorons: Gospel Truth, Rational Supernaturalist, Business Ethics, Christian Morality

"Theology is now little more than a branch of human ignorance. Indeed, it is ignorance with wings." - Sam Harris

The path to Truth lies via careful study of reality, not the dreams of our fallible minds - me

From the sublime to the ridiculous: Science -> Philosophy -> Theology

 This is a response to

 This is a response to BobSpence1: 

 

Dr. John D. McCarthy

Submitted by BobSpence1 on November 12, 2009 - 8:42pm.

 

 

 

You write:

"According to my first argument, I would start with A * A * B * B =  A * (B * B) = A * A * (B2)

I would then replace both B's on the LHS by 1, and decrement the exponent of B on the RHS by 2, in accord with the key assumptions of my 1st approach, that replacing a factor in a multiplication by 1 is equivalent to deleting the factor from the chain, and that the exponent is a count of the number of factors of that value being grouped together under the exponentiation expression.

A * A * 1 * 1 = A * A * (B0)

which clearly is reducible to

1 * 1 = (B0),

or B0 = 1;"

 

I assume that by "the chain" you are referring to the sequence of equations:

 

(2) (((A * A) * B) * B) = (A * A) * (B2)

PROOF OF (2): ((A * A) * B) * B) = (A * A) * (B * B) = (A * A) * (B2).

(1) (A * A) * B) * 1) = (A * A) * (B1)

PROOF OF (1): ((A * A) * B) * 1) = (A * A) * (B * 1) = (A * A) * B = (A * A) * (B1).

(0) (((A * A) * 1) * 1) = (A * A) * (B0)

 

Or are you referring to some other chain?

 

You write:

"According to my first argument, I would start with A * A * B * B =  A * (B * B) = A * A * (B2)

I would then replace both B's on the LHS by 1, and decrement the exponent of B on the RHS by 2, in accord with the key assumptions of my 1st approach, that replacing a factor in a multiplication by 1 is equivalent to deleting the factor from the chain, and that the exponent is a count of the number of factors of that value being grouped together under the exponentiation expression."

 

Assumption 1: replacing a factor in a multiplication by 1 is equivalent to deleting the factor from the chain.

 

Assumption 2: the exponent is a count of the number of factors of that value being grouped together under the exponentiation expression.

 

My understanding of Assumption 1: replacing D * E * F with D * E is the same thing as replacing D * E * F with D * E * 1. 

 

If this is a correct understanding of Assumption 1, then Assumption 1 is well-established. It follows from the fact that

G * 1 = G for every real number, G (the so-called multiplicative identity axiom). 

 

My understanding of Assumption 2: In X * Y^n, where X and Y are real numbers and n is a nonnegative integer, then n stands for the number of factors of Y being grouped together under the exponent n. 

 

So far, my understanding of Assumption 2 is only an observation about the notational usage of n in Y^n. 

 

If I want to compute X * (Y^n), (such as for example I might want to do if I were trying to check the veracity of some equation such as, for example, Z = X * (Y^n)), then I need to know what number is being represented by the notation Y^n. 

 

Everyone is agreed about what number is being represented by the notation Y^n, when Y is a real number and n is a positive integer. The disagreement has been about what number is being represented by the notation Y^n, when Y is a real number and n is a positive integer. 

 

I don't see how to verify the veracity of Step (0) in the above sequence: 

(2) (((A * A) * B) * B) = (A * A) * (B2)

(1) (A * A) * B) * 1) = (A * A) * (B1)

(0) (((A * A) * 1) * 1) = (A * A) * (B0)

 

The fact that the 0 in B0  is a count of the number of factors of B being grouped together under the exponent 0 does not tell me what number is being represented by (B0).

 

Hence, how am I able to verify Step (0) in Steps (2), (1), and (0) above?

It seems to me that in order to verify Step (0) I need to know something more about B0  than that 0 is a count of the number of factors of B being grouped together under the exponent 0.

 

Perhaps, you can tell me some other things than what I can think of at the moment that would allow me to verify step (0). I can come up with two things right now: 

(I) a definition of B^0 as being equal to 1

 

(II) an assumption that the pattern found in Steps (2) and (1), (a pattern which can be established by the agreed upon definition of B^n when B is a real number and n is a positive integer, as I did in the proofs of Steps 2 and 1), continues to hold in Step (0). 

 

As I said, perhaps you have yet another thing that would allow me to verify Step (0).

 

If so, then I would be interested in hearing what is this other thing (or things).


Sincerely,


Dr. John D. McCarthy 
  


 

 

BobSpence's picture

Dr. John D. McCarthy

Dr. John D. McCarthy wrote:

 This is a response to BobSpence1: 

 

 

Dr. John D. McCarthy

Submitted by BobSpence1 on November 12, 2009 - 8:42pm.

 

 

 

 

 

You write:
 

"According to my first argument, I would start with A * A * B * B =  A * (B * B) = A * A * (B2)

I would then replace both B's on the LHS by 1, and decrement the exponent of B on the RHS by 2, in accord with the key assumptions of my 1st approach, that replacing a factor in a multiplication by 1 is equivalent to deleting the factor from the chain, and that the exponent is a count of the number of factors of that value being grouped together under the exponentiation expression.

A * A * 1 * 1 = A * A * (B0)

which clearly is reducible to

1 * 1 = (B0),

or B0 = 1;"

 

 

I assume that by "the chain" you are referring to the sequence of equations:

Or are you referring to some other chain?

NO.

I was referring to the chain of factors in any one repeated multiplication expression.

Quote:
 

 

 

You write:

"According to my first argument, I would start with A * A * B * B =  A * (B * B) = A * A * (B2)

I would then replace both B's on the LHS by 1, and decrement the exponent of B on the RHS by 2, in accord with the key assumptions of my 1st approach, that replacing a factor in a multiplication by 1 is equivalent to deleting the factor from the chain, and that the exponent is a count of the number of factors of that value being grouped together under the exponentiation expression."

 

 

Assumption 1: replacing a factor in a multiplication by 1 is equivalent to deleting the factor from the chain.

 

Assumption 2: the exponent is a count of the number of factors of that value being grouped together under the exponentiation expression.

 

My understanding of Assumption 1: replacing D * E * F with D * E is the same thing as replacing D * E * F with D * E * 1. 

 

If this is a correct understanding of Assumption 1, then Assumption 1 is well-established. It follows from the fact that

G * 1 = G for every real number, G (the so-called multiplicative identity axiom). 

 

My understanding of Assumption 2: In X * Y^n, where X and Y are real numbers and n is a nonnegative integer, then n stands for the number of factors of Y being grouped together under the exponent n. 

 

So far, my understanding of Assumption 2 is only an observation about the notational usage of n in Y^n. 

 

If I want to compute X * (Y^n), (such as for example I might want to do if I were trying to check the veracity of some equation such as, for example, Z = X * (Y^n)), then I need to know what number is being represented by the notation Y^n. 

 

Everyone is agreed about what number is being represented by the notation Y^n, when Y is a real number and n is a positive integer. The disagreement has been about what number is being represented by the notation Y^n, when Y is a real number and n is a positive integer. 

That statement must be a typo.

You just said "Everyone is agreed about                "what number is being represented by the notation Y^n, when Y is a real number and n is a positive integer".

And then said "The disagreement has been about "what number is being represented by the notation Y^n, when Y is a real number and n is a positive integer"

The two underlined sections are identical....

Quote:

I don't see how to verify the veracity of Step (0) in the above sequence: 

(2) (((A * A) * B) * B) = (A * A) * (B2)

(1) (A * A) * B) * 1) = (A * A) * (B1)

(0) (((A * A) * 1) * 1) = (A * A) * (B0)

 

The fact that the 0 in B0  is a count of the number of factors of B being grouped together under the exponent 0 does not tell me what number is being represented by (B0).

Hence, how am I able to verify Step (0) in Steps (2), (1), and (0) above?

Dividing both sides of equation (0) by (A * A) shows precisely what (B0)  must be for that equation to be valid. "The fact that the 0 in B is a count of the number of factors of B being grouped together under the exponent 0" is not intended to tell you "what number is being represented by (B0).", the solution of the equation formed with the help of that assumption is intended to do that.

Quote:

It seems to me that in order to verify Step (0) I need to know something more about B0  than that 0 is a count of the number of factors of B being grouped together under the exponent 0.

Perhaps, you can tell me some other things than what I can think of at the moment that would allow me to verify step (0). I can come up with two things right now: 

(I) a definition of B^0 as being equal to 1

That sequence of equations leading to (0) is simply one way to calculate what a plausible and consistent value of B0 would be.

It does not require any assumption about the value of B0, it proceeds to calculate it.

Quote:

(II) an assumption that the pattern found in Steps (2) and (1), (a pattern which can be established by the agreed upon definition of B^n when B is a real number and n is a positive integer, as I did in the proofs of Steps 2 and 1), continues to hold in Step (0). 

As I said, perhaps you have yet another thing that would allow me to verify Step (0).  

If so, then I would be interested in hearing what is this other thing (or things).

Sincerely,

Dr. John D. McCarthy 
 

 

Favorite oxymorons: Gospel Truth, Rational Supernaturalist, Business Ethics, Christian Morality

"Theology is now little more than a branch of human ignorance. Indeed, it is ignorance with wings." - Sam Harris

The path to Truth lies via careful study of reality, not the dreams of our fallible minds - me

From the sublime to the ridiculous: Science -> Philosophy -> Theology

This is a response to

This is a response to BobSpence1:

Dr. John D. McCarthy

Submitted by BobSpence1 on November 13, 2009 - 2:51pm.

 

You write, regarding my inquiry concerning a "chain", which I thought referred to a chain (sequence) of equations:

 

"NO.

I was referring to the chain of factors in any one repeated multiplication expression."


Thank you for clearing me up on that.

 

You write:

 

"That statement must be a typo.

You just said "Everyone is agreed about                "what number is being represented by the notation Y^n, when Y is a real number and n is a positive integer".

And then said "The disagreement has been about "what number is being represented by the notation Y^n, when Y is a real number and n is a positive integer"

The two underlined sections are identical.."


You're correct about this; it's another unfortunate typo. So much for cut and paste. I meant to replace "and n is a positive integer" with "and n is equal to 0".

 

You write:

"Dividing both sides of equation (0) by (A * A) shows precisely what (B0)  must be for that equation to be valid. "The fact that the 0 in B is a count of the number of factors of B being grouped together under the exponent 0" is not intended to tell you "what number is being represented by (B0).", the solution of the equation formed with the help of that assumption is intended to do that."

 

I assume that you are indicating here that the assumption that the 0 in B is a count of the number of factors of B being grouped together under the exponent 0 helps you to form the equation in Step (0), the equation which you use to calculate that B0 = 1.

How does the assumption that the 0 in B is a count of the number of factors of B being grouped together under the exponent 0 help you to arrive at Step (0)?


I was inquiring into how one arrives at Step (0) and how someone else can verify that Step (0) was arrived at before one uses Step (0) to deduce that B0 = 1. Some one else who is trying to follow your argument will want to verify that Step (0) was arrived at before they move onto the next step in your argument (i.e. the calculation of B0 ).

 

Some one who is following this sequence: 

(2) (((A * A) * B) * B) = (A * A) * (B2)

(1) (A * A) * B) * 1) = (A * A) * (B1)

(0) (((A * A) * 1) * 1) = (A * A) * (B0)

 

needs to be able to verify that each step in this sequence has been arrived at. How is someone else able to follow the sequence from the already arrived at Steps (2) and (1) to Step (0) without having some additional information about what number the notation B0 represents or some additional assumption about the evident pattern in Steps (2) and (1) holding when we pass to Step (0)? 

 

From what you have told me about what you are doing, I assume that you would not use the equation B0 = 1 to arrive at Step (0). So, then, what are you using to arrive at Step (0)?

 

You write:

"That sequence of equations leading to (0) is simply one way to calculate what a plausible and consistent value of B0 would be.

It does not require any assumption about the value of B0, it proceeds to calculate it."

I have two questions.

 

First of all, how does the sequence of equations lead to (0)? I can follow Steps (2) and (1). Why can I do this? Because I can verify Steps (2) and (1) as a consequence of what everyone agrees about the meaning of B^2 and B^1. But I don't follow Step (0).

 

How is the sequence of equations "leading to (0)"? How are you leading us to Step (0) without either assuming some value for B0, or presuming that a pattern is holding from the established Steps (2) and (1) to Step (0)?

 

Perhaps, I'm being a bit slow here. I don't follow the sequence from the established Steps (2) and (1) to Step (0).

 

You say that "it proceeds to calculate it". The calculation which you are doing to get that B0 = 1 uses Step (0). So your argument depends upon arriving at Step (0). How are you arriving at Step (0)?  I don't see how to do this without assuming something about the value of B0 or presuming some pattern is holding from the established Steps (2) and (1) to Step (0).

 

I think that I will be able to follow you in making your calculation, once you tell me how it is you are getting Step (0). Perhaps, you have already told me this and I missed your telling me this. If so, would you kindly repeat how you are getting Step (0)? If not, would you kindly tell me anyhow? I don't see how to do this without assuming something about the value of B0 or presuming some pattern is holding from the established Steps (2) and (1) to Step (0).


Sincerely,

 

Dr. John D. McCarthy

 

 

Wonderist's picture

Holy overblown verbiage, Bat

Holy overblown verbiage, Bat Man!

It's not "A times itself n times," it's "1 times A, n times."

The first definition fails because A^2 = A * A is not A times itself 2 times, it's only A times itself 1 time. Multiplication is a binary operation, remember.

Try this. Copy the following Javascript code into your browser's address bar. The first is 3^3, the next 3^2, then 3^1, then 3^0. (Copy the entire line. Sorry, couldn't make them URLs.)

javascript: function exp(a, n) { val = 1; while(n-- > 0) val *= a; return val;} exp(3,3);

javascript: function exp(a, n) { val = 1; while(n-- > 0) val *= a; return val;} exp(3,2);

javascript: function exp(a, n) { val = 1; while(n-- > 0) val *= a; return val;} exp(3,1);

javascript: function exp(a, n) { val = 1; while(n-- > 0) val *= a; return val;} exp(3,0);

 

Wonderist on Facebook — Support the idea of wonderism by 'liking' the Wonderism page — or join the open Wonderism group to take part in the discussion!

Gnu Atheism Facebook group — All gnu-friendly RRS members welcome (including Luminon!) — Try something gnu!

This is a response to:  Dr,

This is a response to:
 

Dr, John D. McCarthy

Submitted by BobSpence1 on November 11, 2009 - 3:36am.

 

You write, quoting me and then responding to the quote:

BEGINNING OF QUOTE OF ME:

"For instance:

"Multiplying any number A by

Submitted by BobSpence1 on November 6, 2009 - 7:42am.

Multiplying any number A by any number B zero times leaves A unchanged:

A  *  (B0) = A 

Therefore (B0) = A/A = 1."

This argument has all the hallmarks of a deduction, not a motivation. The colon indicates an equivalence; what comes before the colon is presented as implying what comes after the colon. It appears as if it is saying:

STATEMENT: Multiplying any number A by any number B zero times leaves A unchanged. That is to say, A  *  (B0) = A.

 

I can believe that this is not what you intended to do; but I think that it is fair to say that it certainly appears that way. If this is not what is being done, then how did you get from what comes before the colon to what comes after the colon?"

END OF QUOTE FROM ME


YOUR RESPONSE TO THIS QUOTE FROM ME:

"It is a deduction, and was meant to be a deduction. I don't quite know what you mean by a "motivation" here. It does require acceptance of the idea that "Multiplying any number A by any number B zero times leaves A unchanged", which in ordinary terms is a perfectly comprehensible statement, whatever technical problems you may have with in the strictest formal mathematical terms."

END OF YOUR RESPONSE.

By a motivation, I mean the sort of thing that the Wikepedia article does:

"Wikipedia wrote:

Notice that 31 is the product of only one 3, which is evidently 3.

Also note that 35 = 3·34. Also 34 = 3·33. Continuing this trend, we should have

31 = 3·30.

Another way of saying this is that when n, m, and n − m are positive (and if x is not equal to zero), one can see by counting the number of occurrences of x that

 \frac{x^n}{x^m} = x^{n - m}.

Extended to the case that n and m are equal, the equation would read

 1 = \frac{x^n}{x^n} = x^{n - n} = x^0

since both the numerator and the denominator are equal. Therefore we take this as the definition of x0."

 

In this article from Wikepedia, an exponential law that holds "when n, m, and n − m are positive (and if x is not equal to zero)" is used as a motivation for defining x^0 to be equal to 1. The article does not deduce the equation:

 1 = \frac{x^n}{x^n} = x^{n - n} = x^0

from the preceding equation:
 

 

 \frac{x^n}{x^m} = x^{n - m}.
which at this point in the Wikepedia's article has only been established "when n, m, and n − m are positive (and if x is not equal to zero)". Instead it discusses what would happen if one were to continue "this trend" (i.e. this pattern) or how the equation "would read" if one took the equation "Extended to the case that n and m are equal".

This is what I mean by a motivation. The Wikepedia article does not present the argument as a deduction that x^0 = 1, except insofar as the argument appeals to what follows from an assumption that a pattern continues.

The essence of the argument is this: If "this trend" continues or if the equation is "Extended to the case that n and m are equal", then it follows that 1 = ... = x^0.

In other words, the essence of the argument is that: Assuming that "this trend" continues or the equation is "Extended to the case that n and m are equal, then it follows that 1 = .... = x^0.

Or to put it differently, the essence of the argument is that: Assuming that a certain pattern continues, then it follows that 1 = .... = x^0. The argument demonstrates that the assumption that a certain pattern continues implies that x^0 = 1.

The argument uses this demonstration to motivate the definition that x^0 = 1: "Therefore we take this as the definition of x^0."

This is what I mean by using the term "motivation".

Again, regarding your argument:

"Multiplying any number A by any number B zero times leaves A unchanged:

A  *  (B0) = A 

Therefore (B0) = A/A = 1."

you write:

"It is a deduction, and was meant to be a deduction. I don't quite know what you mean by a "motivation" here. It does require acceptance of the idea that "Multiplying any number A by any number B zero times leaves A unchanged", which in ordinary terms is a perfectly comprehensible statement, whatever technical problems you may have with in the strictest formal mathematical terms."

 

I'm missing the deduction. I have elsewhere freely granted that "Multiplying any number A by any number B zero times leaves A unchanged" is evident. The question is how does that imply that "A * (B^0) = A". It would appear that such an implication would depend upon establishing that multiplication of A by B^0 is the same thing as multiplying A by B zero times. Otherwise, I don't see any connection between the premise "Multiplying any number A by any number B zero times leaves A unchanged" and the statement that you are claiming to deduce from the premise:  "A * (B^0) = A".

How are you getting that multiiplication of A by B^0 is the same thing as multiplying A by B zero times? What definition of B^0 are you using at the point where you deduce that multiiplication of A by B^0 is the same thing as multiplying A by B zero times? You must be using something about B^0 to make this deduction. What is it about B^0 that you are using to make this deduction?

 

You write:

"I was not trying to address Samuel on the details of his argument, just showing that, unless he could find a logical flaw in that STATEMENT, which there isn't, he has to accept that there must be some flaw in his argument."

Here, when you refer to "that STATEMENT", I assume that you are referring to your statement:

"STATEMENT: Multiplying any number A by any number B zero times leaves A unchanged. That is to say, A  *  (B0) = A."

I'm pretty sure that Samuel would have no problem with the first part of this STATEMENT: "Multiplying any number A by any number B zero times leaves A unchanged." I have not noticed any one in this thread challenging that part of this STATEMENT.

But I wonder whether Samuel, like myself, might ask you how are you getting from the first part of this STATEMENT to the second part of this STATEMENT: "That is to say, A * (B^0) = A."? 

I'm not following the deduction here.

You write:

"The basic 'assumption' in the STATEMENT is that performing some operation zero times is exactly equivalent to not doing it, just another way of saying the same thing."

Again, just so you don't misunderstand me here, I have no problem with this "basic 'assumption' in the STATEMENT (i.e. the first part of the STATEMENT). What I am not following is how you get from the first part of the STATEMENT to the second part of the STATEMENT.

Quoting again from a post of mine and responding you write:

QUOTE FROM ME:

"So why shouldn't the pattern that: 

(1) A * (B^3) is the same thing as multiplying A by B three times,
(2) A * (B^2) is the same thing as multiplying A by B two times,
(3) A * (B) is the same thing as multiplying A by B one time,

break down when we get to multiplication of A by B^0? This is actually a very good question that Samuel asks. Indeed, why shouldn't it break down? Why should we expect anything different than that it might break down? Samuel had seen a number of fallacious attempts at showing that A^0 = 1, all of which were based upon an unwarranted assumption that a certain pattern (which Samuel refers to as "the shortcut" were sustained when we get to the power of zero. Samuel rightly saw that these arguments were circular reasoning."

END OF QUOTE FROM ME.

YOUR RESPONSE TO THIS QUOTE FROM ME:

"The pattern actually breaks down at (3), for n = 1, because the the definition of exponentiation in terms of multiplication operations."

 

There appears to be a typo in (3). I meant to write:

"(3) A * (B^1) is the same thing as multiplying A by B one time"

Since there has been no disagreement here over whether B^1 = B or not, I think that the pattern holds up at (3). If someone was using a different definition of B^1 than that B^1 = B, then I could see that the pattern might break down at (3).

Just to be clear, the pattern to which I am referring is this pattern: A * (B^n) is the same thing as multiplying A by B n times, a pattern which is illustrated by (1), (2), and (3).

You write, beginning with a couple of quotes from Samuel:

 

"Samuel wrote:

 The exponent, the power, the smaller number floating above, is meant to tell you how many times the base number should be multiplied by itself. 

Samuel wrote:

 "To the power" means you multiply the base by itself the number of times shown by the exponent.

Both of which are incorrect on two counts:

1. Exponentiation is only defined in terms of repeated multiplication for the case of positive integers n > 1, not applicable for n <= 1;

2. For such values of n, the number of multiplication operations implied is n - 1, NOT n.

I will also remind you of this

Dr John D. McCarthy wrote:

Now according to the Wikepedia article, A^n is the result of multiplying A repeatedly by A n times. With this definition, it follows that A^0 is the result of multiplying A by A 0 times.

I pointed out then, and I will repeat, that that is not an accurate description of what that Wikipedia article said.

If the Wiki statement was as you describe it, it would indeed lead to that conclusion, but it does not say that. It says explicitly that An is the result of repeated multiplication, and uses diagrams to show that this involves n instances of A, NOT multiplying n times, for n an integer greater than 0. This conflation is at the core of Samuel's error.

Let me repeat: you are making errors, and you have yet to acknowledge this."

I have previously pointed out what I was doing at this point; namely, I was sticking to the terminology that Samuel had used, understanding that by multiplying "the base by itself the number of times shown by the exponent" he meant to take n factors of the base and multiplying them. I explained that I thought that this was clearly what Samuel meant by the explicit examples which he gave: 3 x 3 x 3 = 3^3 and 3 x 3 = 3^2.

In addition, I have elsewhere apologized to sticking to Samuel's terminology, recognizing that I clouded the discussion by doing so.

You write quoting from me and responding:

QUOTE FROM ME:

I don't think that Samuel would have seen your argument as anything different. I think that he would have seen your argument as just another example of circular reasoning; just another example of making an unwarranted assumption about a pattern being sustained.

END OF QUOTE FROM ME


YOUR RESPONSE TO THIS QUOTE FROM ME:

He would have no justification for such a conclusion, because I did not base my later argument on any thing about patterns - I based it on that STATEMENT above, that performing an operation zero times is equivalent to not performing it, which I still maintain is logically self-evident. Plus the repeated acknowledgement that ultimately it has been decided to define A0 = 1, chosen because it is consistent with various deductive arguments, and fits the pattern. This could be expressed as the definition being chosen to make that pattern consistent, rather than a unjustified extrapolation from the pattern.

 

END OF YOUR RESPONSE.

 

First of all, had you stated, in language similar to the way that Wikepedia argued, that you were extending or continuing an established pattern to see where it lead and then said something like "Therefore we define B^0 = 1." then there definitely would be no justification for Samuel to charge you, as he charged the mathematician, with circular reasoning. Why not? Because there is nothing circular about investigating the consequences of an assumption and then deciding to define A^0 in a certain way motivated by these consequences.

The germ of truth in Samuel's charge was that he had heard arguments from those he regarded as mathematical authorities which purported to deduce that A^0 is equal to 1.

Again, I don't think anyone has challenged whether "performing an operation zero times is equivalent to not performing it". I'll grant you that this is "logically self-evident". The question remains, however, how do you get from this part of the STATEMENT (i.e. the first part of the STATEMENT) to the second part of the STATEMENT (i.e. A * (B^0) = A)?

I think that it is at this step, going from the first part of the STATEMENT to the second part of the STATEMENT, that Samuel is going to be looking for justification.

How do you get from the first part of the STATEMENT to the second part of the STATEMENT without using either that B^0 = 1 or that a certain pattern continues to hold when n = 0? I'm at a loss to provide a justification for this step without using one or the other of these two things. If you have an alternative justification, then I would be interested in hearing about it.

You write, quoting me and then responding:
 

QUOTE FROM ME:

"ARGUMENT: Suppose that x/(x - 1) = 1/(x - 1). Then, by multiplying both sides of this equation by (x - 1) it follows that 

(x/(x _ 1))(x - 1) = (1/(x - 1))(x - 1). That is to say, x = 1. Hence, x = 1 is the solution of the equation x/(x - 1) = 1/(x - 1).

END OF ARGUMENT

 

With such examples the students are taught the fallacy of backwards reasoning. They find such examples to be quite surprising, since they have been taught in pre-college to use this fallacy to solve equations. I myself was taught to use this fallacy in my earlier education. It is quite common to use this fallacy in arguments."

END OF QUOTE FROM ME

YOUR RESPONSE TO THIS QUOTE FROM ME:

"Curious. I see no "fallacy of backwards reasoning" in that example."

END OF YOUR RESPONSE

This is the backwards reasoning to which I am referring.

Consider again the ARGUMENT:

ARGUMENT - PART I: Suppose that x/(x - 1) = 1/(x - 1). Then, by multiplying both sides of this equation by (x - 1) it follows that 

(x/(x _ 1))(x - 1) = (1/(x - 1))(x - 1). That is to say, x = 1.

END OF ARGUMENT - PART I

What does this ARGUMENT - PART I prove? It proves the following conditional statement:

CONDITIONAL STATEMENT 1: If x/(x - 1) = 1/(x -1), then x = 1.


Since a conditional statement is logically equivalent to its contrapositive, CONDITIONAL STATEMENT 1 is logically equivalent to the following conditional statement:

CONDITIONAL STATEMENT 1': If x is not equal to 1, then x/(x - 1) is not equal lto 1/(x - 1).

 

In other words, the ARGUMENT - PART I proves that if a number is not equal to 1, then it is not a solution of the equation x/(x - 1) = 1/(x - 1).

Let's break down CONDITIONAL STATEMENT 1 into its skeletal form:

CONDITIONAL STATEMENT 1: If P, then Q.

P: x/(x - 1) = 1/(x - 1).

Q: x = 1.

 

Now let's look at what the person who wrote this ARGUMENT said followed from this ARGUMENT:
 

ARGUMENT - PART II: Hence, x = 1 is the solution of the equation x/(x - 1) = 1/(x - 1).

END OF ARGUMENT - PART II


What does the conclusion of ARGUMENT - PART II mean? That is, what does it mean to say that x = 1 is the solution of the equation x/(x - 1) = 1/(x - 1)? More specifically, what does it mean to say that x = 1 is a solution of the equation

x/(x - 1) = 1/(x - 1)?

 

It means nothing more, nothing less, than this:

CONDITIONAL STATEMENT 2: If Q, then P.

Q: x = 1.


P: x/(x - 1) = 1/(x - 1).


Thus, the "Therefore, ...." in ARGUMENT - PART II is the claim that having proven that "If P, then Q." it follows that "If Q, then P."

This is what I am referring to by the phrase "backwards reasoning"; the idea that I can establish "If Q, then P." by proving "If P, then Q.".

This idea is a common logical fallacy. It is commonly taught to students in pre-college algebra classes. Students are taught to start with the desired conclusion and reason to the given hypothesis; and then conclude that they have "solved" the algebraic problem. They have done no such thing at that point. All they have done is they have proven something like "If x is not equal to 1, then x/(x - 1) = 1/(x - 1)." when what they have to show in order to show that x = 1 is a solution is "If x = 1, then x/(x - 1) = 1/(x - 1)."; which, of course, cannot be shown.

This logical fallacy is commonly referred to as backwards reasoning. It takes some doing to cure my students of this fallacy. They wonder why they get the wrong answers. The reason for this is that they are engaging in this sort of backwards reasoning. 

You write:

"Multiplication of both sides by the same factor is valid, as long as that factor is non-zero. Since it turns out to be zero for the apparent solution, that shows that in this case that solution is not valid."

I nowhere challenged the validity of ARGUMENT - PART I. ARGUMENT - PART I is a completely logically valid demonstration of CONDITIONAL STATEMENT 1:

CONDITIONAL STATEMENT 1: If P, then Q.

P: x/(x - 1) = 1/(x - 1).

Q: x = 1.

 

The backwards reasoning occurs in ARGUMENT - PART II.

You write:

"If you reduce the equation by subtracting both sides by 1/(x - 1), you get  (x - 1)/(x - 1) = 0 which implies that (x - 1), and therefore x, is what we describe in computing as NaN (Not a Number)."

I suspect that there is a typo here. It's not clear to me what you were intending to say here.


Sincerely,

Dr. John D. McCarthy