I just realized there is another level of potential confusion here, to do with two distinct uses of 'probability'.

One use is to describe the behaviour of random processes, like the decay of atoms, or processes so sensitive to small variations in various conditions that there behaviour in any one instance is essentially unpredictable, like coin tosses or throws of a dice.

The other is where a particular 'fact' about the universe may well have a quite well-defined value, but we do not have ways to measure or observe it directly enough to establish this value precisely. It may be historical, so we are left to forensically analyse whatever traces it may have left in currently observable data, or very far away, or only measurable thru very indirect means, or the observation is likely to be affected by other factors by an uncertain amount.

In the latter case, we have to evaluate from the limited data we do have what is the most likely value it may have, in our estimation. This requires us to think of what other factors would affect our observations, and what are the probabilities of various combinations of all the things affecting our measurement having just the particular values to give us the value we actually measure.

If we are measuring the intensity of light from a distant star we have to consider allow for the amount of dust and gas that may be between us and the star. We will use other information we may have which estimate the distribution of such dust and gas in that region of space, and our estimate of the distance of the star, to estimate the likely amount of absorption and scattering the light may have suffered on its way to us.

This piling of uncertainty on uncertainty may seem to lead us to total ignorance of the 'true' value of any such measurement. But in fact we are 'saved' by the fact that we have a multitude of measurements of many aspects of the stars and the stellar environment, some of which are relatively well nailed down, and by cross comparing related data we can usually keep the uncertainty within bounds.

Any uncertainty in the 'true' value of a physical measurement is unlikely to be infinite, so we can normally set some upper and lower limit from very crude observations. We were able to devise quite useful electrical equipment without knowing the precise value of the charge of an electron or the exact values of the conductivity of the wires used.

So absence of precise knowledge does not leave us in total ignorance. Call it a false dichotomy, perhaps.

Yes! Lack of proof does not equal lack of evidence. So we have two lines of attack on this notion that, because of the problem of induction, atheists have no more grounds for their position than theists.

1. The problem of induction is a problem in logic, but logic is not sufficient to make inquiries about the natural world. We can "trump" the problem of induction by invoking parsimony and noting that the logical problem never seems to become a real-world problem. The problem of induction would seem to point to a flaw in our thinking, not to any inherent uncertainty in the world.

2. The problem of induction presents a problem only for those seeking mathematical proofs and 100% correct answers. There still exist high levels of certainty (as high as our certainty that the sun will come up, and higher) that, while falling short of the Absolute, are more than convincing enough to motivate all our beliefs and actions. Atheists can claim a much higher level of certainty for the truth of their position than theists can for theirs.

I'd add that 'uncertainty' about the world merely points to uncertainty, not chaos. And uncertainty simply does not open the door to fideism, or any unsubstantiated leap to a 'god', which is infinitely more problematic, to 'solve' the problem. In short, there's no real 'problem' in the sense TAGers think there is, and the existence of a problem in itself does not grant a justification for just assuming there's a magic pixie that mysteriously solves it.

Tagers actually  have no solution at all to the problem...  TAG is an admission that there is no solution. Ask a TAGer how TAG actually provides justification for induction... they can't, because it doesn't. They merely assert that a black box somehow magically melts the problem away.

To deal with a TAGer, give them a logic textbook and ask them to read it. No one can be both a TAGer and informed in logic.

 They can only follow their instincts.

 We can use logic, but at a fundamental level our beliefs come from what we feels to be true, rather than what we deduce to be true.

And neither can you jump from the good effects of ignoring the problem of induction to asserting that you have rational grounds for assuming induction works. 

But what evidence do you have for anything? Nother other than that it feels that way for you. 

Do you not actually understand the problem in question? 

I actually agree, but then the question is "what does point the way to new knowledge?". My answer is that we follow our instincts and intuitions, rather than any rational process. 

And why is it me that needs to learn what logic is in the first place? I seem to be the only one that is saying that we don't use logic  know the world. In fact Topher directed me here because he claimed that you had shown that induction could be logically justified by simply invoking Bayes' Theorem (which would, if it were true, give us a way of knowing the word through logic), which turned out not to be true, as it obviously never was going to be. Now unless you can show that empiricism has some rational justification, you have no right to call yourselves rational, nor can you dismiss others arguments on the basis of not being rational (and the same follows for Christians).

And who is a TAGer? You're so rehearsed in giving your anti-Christian, rational worldview that you're incapable of seeing arguments or opinions for what they are.

I'm adding in a principle that you have mistakenly left out of your inquiries. Don't thank me, just send money.

By rejecting Occam's Razor you ignore the fact that there are many more erroneous conclusions to be drawn from a given set of data than correct conclusions. This is a mathematical principle, in fact, and the Razor is there to deal with it. Ignoring this principle seems to me to be quite irrational. 

I also thought that this wasn't Philosophy 101 where I'd have to present rational justifications for every well-known and accepted concept I mention. I'd say the onus is on you to tell us why we should throw the idea of parsimony out the window, then explain how you would deal with the fact that there are multiple incorrect answers for every correct one in a condition of incomplete data.

No, we worked out the basic fundamentals of what is true billions of years ago when the earliest life forms found out through trial and error what kept them alive and what killed them. Basic truth, such as the fact that you can safely ignore the problem of induction, has been drummed into us by the very phenomenon we are trying to investigate: the natural world.

You are simply asserting that only logical and mathematical proofs can be associated with reason, and that anything not reducible to them fails the test of rationality. Your definitions of reason and rationality are too narrow and don't reflect how most people use the words.

rational 1. Able to reason. 2. Not foolish or absurd, sensible, reasonable. 

I and many others keep pointing to the other things, like induction, and ways of assessing balance of probabilities, including ways of refining and rendering somewhat more rigorous our somewhat subjective estimates of likelihood of various proposed explanations.

LJoll seems trapped in this very narrow idea of 'rational', and unable to grasp that we have developed new tools of thought in addition to basic logic, which do not contradict that logic, but have greater analytic power.

How is it not 'rational' to act on the probabilistic predictions of these tools, when they continue to power the massive advances in scientific understanding and technological progress we have experienced? 

It would appear that LJoll is only listening to his (uninformed) instincts and intuitions rather than his 'reason'. 

Nice strawman - I never said any such thing 

I can justify my premises by observation. You just dont seem to understand what the word "justfication" actually means. You seem to be confusing it with absolute certainty or logical proof. 

Observation of patterns within the universe and the meta observation that the universe does indeed have order. You observer this and you accept this premis even if you dont wnat to admit it. To even have concepts such as

Object, self, univere, time or pretty much anything an order is implicit. If you deny that there is any order, or suggest that it is irrational to think so then ANYTHING that relies on any of these concepts is also irrational. As everything we cna concvieve of will rest on these then EVERYTHING turns out to be irrational. This renders the term (ir)rational completely meaningless. 

I think you need to have little ponder about what it is to be rational. You seem to be stuck on this idea that rationality can only stem from deductive logic. You are wrong. Most philsophers woudl agree that you are wrong. You need to educate yourself.

Indeed well done thats right. Induction does not follow from logical deduction (I'm not going to say reasoning because there is more to reasoning than just deduction). But so what? You are making the claim that induction is irrational you are not making the claim that deduction is a process not logically deducable.  

Again you are mixing up terms. Now you bringing "knowledge" into it. This is a confusion on your part. I don't know for certain that it will be BUT it is a reasonable assumption based on the evidence from the past. The laws of physics have not changed ever as far as we know. Now they might change - it possible I suppose and your right there is no way of knowing for certain but now we have two possabilities

1- The laws of phsyics will be the same tomorrow (as they have alwasy been)

2- The laws of phsyics will change tomorrow

I have agreed we can not know for certain which of these is true. But which is more likely?  Which is it rational to believe? If you genuinly believe that 2 is just as likely as 1 then you are insane.

So you cant. Right what does this tell you? 

I see so in other words you cant think of a counter argument so you are throwing your toys out of your pram and refusing to play. 

Grow up. Then perhaps we can have a sensible discusion I have no time for children.

I can't be bothered replying to every single post, so how about this. Can anyone explain iin detail how we may obtain knowledge of the future (probabilistic or certain), without making any unjustified assumptions?
 If you can, I'll admit that I'm wrong. All I am arguing is that no objective method follows rationally from something that we can know with certainty.

Another quite point that a few people (or at least one person repeatedly) haave got wrong. Occam's razor does NOT follow mathematically from the fact that there are many more incorrect conclusions than corect ones. Why would it? It is just an intuitive way of viewing data.

I'm going to go out on a limb here and assume that you will agree that modes of thought which allow us to think and react to our environment, and thereby preserve our lives, are "justified" along rational lines. I hope you will agree that modes of thought which, if followed, would result in mental paralysis and death are absurd and nonsensical. I want to clear this up, because we are having a tough time pinning you down to exactly what you mean by "rational" and "justified."

If you are talking only about justification through pure logical deduction, the point has been made several times that you are applying logic inappropriately, and brushing aside other methods of reasoning that are equally valid.

You say it is invalid to assume that things that were true in the past will be true in the future. What if we look at ourselves in the past and examine what would have happened if we employed that mode of thought? For instance, instead of sticking your keys into your car to start it in the morning, assuming that it would work as it had before, you instead did a complete check of the engine to make sure it wasn't going to explode on ignition. We can see that the consequence of that would be that you would have lost your job by now, having never arrived before noon each day. Today, this morning, you are faced with the same problem. Check the engine, or just try to start the car? In light of what you know the consequence of checking the engine will be, does it make more sense to focus on the fact that you have no logical proof that the engine will work, or does it make sense to make a pragmatic concession that your action is logically flawed but you are going to try it anyway? At one level, yes, you are acting without regard for logic. At the larger, and I would say more relevant level, you are taking the more rational approach in light of the big picture. Your action is justified, because it results in the outcome you want. 

Occam's Razor is justified the same way. You walk into your house and see the newspaper that you left on the kitchen table is now lying on the floor. There is one correct explanation for it, and myriad incorrect ones that still fit the available data. But if you stand there examining and eliminating all the alternative theories rather than choosing the simplest one and going forward, you will be dead of starvation before you decide that the cat probably knocked it off. Embracing a mode of thought that allows you to think and act is much more rational than insisting on a logical purity that leaves you paralyzed.

And I'm not talking about specific beliefs, but rather about rules for creating beliefs. What we all need is a functioning belief-creating system that delivers the results we need to stay alive. Logic is very much a second-order aspect of that system, one that is invented only after the fact to help us conduct discourse.  

You are being sloppy with your terms again. I am saying that only rational explanations have a hope of being valid. I am also saying that we do not necessarily need to discard our rational conclusions if we are unable to defend them using deductive logic. There are other ways to be rational than deductive logic alone, including inductive logic.

The contingent belief that the engine won't explode is not arrived at "instinctively." It is arrived at by analyzing past data, comparing it to present data, identifying similar patterns and assigning a probability that a pattern of events will be repeated based on the observation that certain events do tend to repeat under certain similar conditions. This is a highly rational process. In fact, if one used only logic to arrive at the conclusion that you aren't sure that the engine is safe, you would be acting irrationally.

I think this is what is getting you into trouble here: you keep swapping "logic," "rationality" and "justification" around as if they are interchangeable. Open the dictionary. These words all have distinct meanings.   

Ok you need to understand what it means to justify something.

Justfication basically comes from observation of the world. That is what we mean when we say something is justified. Think about it for a momment. Think about how you use the word "justify".

If we see that some thing (B) always happens when another thing happens (A)then when we observe A we are justfied in believing that B will also happen. So looking at the world around us we observe that the past resembles the present and hence we can inductivly deduce that the future will continue to obey the same laws. The premises that THIS observation relies upon is that our observations of the universe are actually a reflection of the universe itself AND that there is an external universe indapendant of our mind.

 So in order to make the inductive argument that the past will resemble the future we need to "assume" the following two beleifs

1) Our observations of the universe reflect the actual universe.

2) There is a mind indapendant universe "out there"

If these two things are true then our inductive reasoning is a valid and justfied. So the discusion now actually shifts to an arguemnet between transendental idealism and the varous forms of realism.

Lets take 1 to begin with.

Do our observations reflect the actual universe (if it exists)? Well this is a somewhat tricky subject but I think the most likely explanation is that they do. I need you to note at this stage that our obseravtions do not need to be entirely accurate only that they do generally reflect what is really going on "out there". The reason I say that it is the most likely explanation is as follows.

If we compare the idealist position with the realist positon which is actually consistent with what we experiance? If our observations and experiances are not linked or do not reflect the real world then how is this explained? The realist position is simply explained in that there is phsyical link between our brains and the world our there. Some complex kind of "mapping" of reality is going on which means that our experiances more or less correspond to reality. They may be distorted or twisted in various ways but the will be an imperfect reflection none the less. But how do we explain the idealist position? If our obseravtions really do not tell us anything about what is really happening out there then what is it that we observe? Why do we have such a remarkable correlation between the observations of different minds? Why do our obseravtion more often than not concur with each other? How is this possible? I can't think of any suitable answers to these questions. Hence on the balance of reason I would reject idealism as far less likely than realism.

Next lets take 2. 2 is vital for 1 in fact as well as for the inductivly gleamed notion that the furure resembles the past. So is there a mind indapendant uninverse? Again we need to look at what is more likely given our observations. We have two competing ideas.

1) That the universe is entirely a creation of our minds. That there is no physical reality merely a mental construct.

2) That there is a real mind indapentdant phsyical universe.

Again I would say that 2 is far more likely given the availbale evidence. If we want to accept 1 we need to explain

a) Why the universe appears to be indpaendant of our minds?

b) How is this mental construct created?

c) Why is there correlation between different minds as to the nature of reality?

d) How do we account for that fact that we sometimes get things wrong about the universe and managed to acknowledge this error?

There are other problems but these should be enough I think to indicate that the most likely explanation of the observed phenomona is that there is a mind indapendant universe.

Soooooo

If we accept (for the reasons above)that 

1) Our observations of the universe reflect the actual universe.

2) There is a mind indapendant universe "out there"

Then our observations tell us that the past resembles the future and alwasy has done. This being the case then the principle of induction is a valid method of reasoning.

You need to get away from this obsesion with "certainty". The rational man will deal with the most likely explanations. If we limit ourselves to only certain things then there aint a lot we can discuss about anything really. 

This is a reasonable start, at least it actually attempts to show that we can have reason for believing that induction works, rather that just saying "you'd be dead if you didn't believe in induction", which would be true, but doesn't really show why induction must be (or probably is true).

I have no problem with accepting that the outside world exist or that it is mind independent. I'm not sure that you actually have shown these things to be true, but lets just assume they are for the time being.

So now your argument is that the the laws that govern the universe at a given time have always been the same as the laws governing the universe at a time preceding it. From that you conclude that the same will probably be true in the future. Without assuming induction to be true in the first place, I can only assume you used reasoning similar to this: every observation we have made is evidence of the underlying principle that the laws of nature are uniform. I briefly thought similar reasoning may be some sort of answer, but I quickly realized that it wasn't satisfactory. The same observations are also what you'd expect to see if the laws of nature were uniform until next thursday. In fact the observations support an infinite number of theories, so how do you determine which is correct. Occam's razor? Yet the value Occam's razor is not a mathematical law, it must be justified itself. Now how can Occam's razor be justified without alreaqdy assuming it to be true or for induction to hold?

Sorry. I did not mean certainty. I just meant something that we do not instinctively feel to be true.

 We seem to agree on the most part, except from whether Occam's razor can be rationally justified. Occam's razor feels like it should be true. It is aesthetically pleasing. It appears to have worked in the past (although we can't use this without begging the question0. But how can we use rational methods to show that it must be true. What you've done is show the unpleasing consquences for rational methods that arise if we cannot shoe that occam's razor is true. I do not believe that we can show that rationally, so I have given up trying to have beliefs that are truly rational. Try to show why occam's razor is true if you wish.

What criteria do you think a belief must fulfill to be considered rational? 

Indeed 

I supose so 

Indeed 

I think we can we can look at what it would mean if it where not a valid method fro determining which competing beliefs we shoudl hold. If occams razor is denied as a valid deciding method then we are left with some crazy and indeed absurd conclusions.

The pink pixie theory of the universe is as valid as the relasit one. As is the blue unicorn distupting our minds with its magic horn, the evil scientist with his brain in a vat and any other crazy far feteched scenario that would fit in with the observations. If reasoning or justfication is to mean anything then occams razor must stay.

Indeed rationality and reason itslef crumbles away BUT, and heres the rub, you are using reason to form the agrument against occams razor's validity. 

Again we must not get caught up "tuth" or "certanties". Occams razor is a vital part of rational thought. Without it any explanation we care to imagine no matter how contrived has equal worth. Ponder this scenario

The univers is actually ordered with constant laws

But there are manevolant pixies that muddle the mindss of people and put doubts in there minds that make them doubt sound principles like occams razor.

This scenario is equally likely if we do indeed reject occams razor.  

It must be justfied and be the most likely explanation.

In order to bejustfied it must fit with the observations.

In order to be the most likely it must utlise the least number of assumptions.

The realist position is almost always the winner in this contest. The notion that the laws of the uinverse change makes many additional assumptions over and above the realist position (as outlined above) hence it is less likely and hence in a straight fight it losses. 

Occam's Razor is not true or false. It is not a logical proposition. It is a pragmatic concession to the fact that we never have all the data. THAT DOES NOT MAKE IT LESS NECESSARY OR FUNDAMENTAL TO REASON.

We do not embrace Occam's Razor because we want to, or out of instinct. We embrace Occam's Razor because we have to in order to think. If you wish to assault Occam's Razor, the onus immediately shifts to you to defeat all the possible theories that would support Occam's Razor.

You: I don't think Occam's Razor is valid.

Me: Yes it is, because a purple martian who knows everything told me it is.

You: Come on, that's ridiculous.

Me: OK, tell me why it's ridiculous without using Occam's Razor.

You: I have here a complete history of every millisecond of your life. As you can see, at no time did you talk to a purple martian.

Me: Oh, I forgot to mention that the martian communicates telepathically.

You: Ok, here's a complete history of all the activity in your language centres along with a translation of that activity into thoughts. Still no record of the communication.

Me: Silly me. I neglected to mention that the martian teleported me into a timeless extradimensional space to give me the message, then sent me back to within one Planck-instant of the time I left so that the interval won't show up on your scans.

You: OK, I want the Razor back.

You see? No argument, no theory, no matter how well supported, can survive without the Razor. That includes your own theory that the Razor is unnecessary.

The Razor is a fundamental principle of reason.

Ok. Now this is at least interesting. You seem to be justifying the use of Occam's razor on the grounds that rejecting it would give us no rational grounds for rejecting clearly ridiculous beliefs, such as that there are no pixies that disappear whenever someone looks in their direction. What, then, do you use to show that the belief in pixies is ridiculous? You cannot use Occam's razor, as that is what you're trying to justify in the first place. We can just know intuitively that pixies don't exist. It is this same intuitive sense that gives us the conclusions that Occam's razor formalises and that also tells us that god doesn't exist and that the laws governing the universe tomorrow will be the same as today.

I do not deny all reason. I just deny that most of are conclusions are fundamentally rational.

Not necessarily. The fact that we cannot rationally show one conclusion to be more probable than another does not make both conclusions equally valid. In fact, that seems to be the mistake of many post-modern philosophers.

I don't think this is a very good explanation of what it means for something to be rational. As I mentioned before, there are an infinite amount of explanations that fit the same observations. You cannot judge a theory simply in terms of the amount of assumptions it makes. It is easy to put forward a simple argument such as the malign demon or brain in a vat, which make hardly any assumptions, yet would not be considered likely.

I don't think this is really an explanation of what it means to be rational at all. You're just giving some examples of what you think it's rational to believe.

That's exactly what the Razor does. The principle is that the theory with the fewest unobserved elements is more likely to be true, given competing theories that explain the data equally well. If you discard the Razor, you cannot even defend the theory that the Razor isn't valid without actually collecting data and assigning mathematical probabilities to each hypothetical alternate theory.

But you have a bigger problem. I said that Occam's Razor can be used to support the validity of induction. You said that Occam's Razor itself isn't valid. I pointed out that you can't say that without using Occam's Razor. You have come back and said that you can, because Occam's Razor can be replaced with...induction (assigning probabilities). So now your point that Occam's Razor is not a valid support for induction is supported by induction. So I guess induction wins either way. But you have said that induction amounts to nothing more than wishful thinking. So I guess your whole point rests only on wishful thinking. In other words, we are expected to accept your point that induction is not supported by Occam's Razor only because you want us to and you feel very strongly that this is the case. Sorry, but I need a better rationale than that. Once again, you've sawn off the branch you are sitting on.  

On the other hand, if you, like me, would accept that logical induction is a valid tool for making conclusions, you would also support Occam's Razor because we can observe that it is certainly more probable that a theory with fewer unobserved elements is true. Or, if you, like me, agreed that Occam's Razor is a valid tool for making conclusions, you would support induction because the theory that things that have always been the same will not change requires fewer unobserved elements than the theory that they will change. It's only when you insist that only deduction can tell us anything valid that you are stuck in this quagmire of making statement after statement that is, by your own measure, invalid.

Not difficult...impossible. Every single one of your arguments on this board depends on the use of Occam's Razor as a fundamental assumption. These include any deductive arguments. 

Yes, Occam's Razor does point to a problem with rational argument, namely, that it always occurs in a condition of incomplete information. But this problem exists and must be dealt with. Even basic logical axioms can be refuted by the proposition that you are really a brain in a vat in a universe that works quite differently, but are being fed information that makes the universe seem to work the way it does.

Everything starts with empirical sensation, and the Razor is a basic tool of our consciousness that makes sensation digestible. It is before logic, and logic is contingent upon it. 

You missed the point that Occam's Razor is neither 'true' or 'false'. The proper question is whether it is a useful principle to decide between various theories or propositions which are all 'logically' consistent with other relevant, accepted data.

So the theory that minimises the number of additional assumed entities, attributes, otherwise unsupported ideas appeals to us, of course. This approach minimises the complexity of the total set of explanations we need to provide useful explanations of 'reality'.

By useful, I mean they allow us to design stuff which works, predict the way various things, processes, etc will change over time to an adequate degree of precision, as confirmed by repeated tests and/or observations. So we can design and construct ever more complex artefacts, and explore the Universe in ever more detail.

Of course, in principle, some alternative, vastly more complex, set of theories may prove to be equally 'accurate' and useful, and may even conceivably more accurately reflect 'ultimate reality', but that is really academic. Until a more complex idea can be devised which actually provides better more useful descriptions and predictions, it is eminently rational to run with the simpler set, if only because it is easier to manage and reason with.

There are rational reasons to reject theories that introduce more independent entities and properties that are not otherwise observable, because we have no independent way investigate those extra items.

If we assume intelligent agents like pixies or gods, then we have destroyed, in principle, any useful predictive power of the 'theory' until we come with an exhaustive psychological profile of such agents, IOW yet another theory is required, leading to a version of the 'infinite regress' problem. So in the absence of evidence pro or con these entities we are rationally justified in discarding theories with such elements, really because they are actually more complicated because 'agents' introduce a whole new layer of extra properties, ie those of the agents themselves. It is tempting foe Theists to see God as a 'simpler' explanation, but all they have done is wrap all the complexities inside a convenient label without actually explaining any of them, so it superficially looks like they are proposing 'one' entity.

So we don't actually require our theories to accurately describe ultimate reality, just that they reflect those aspects of Truth that affect us sufficiently well, even if only by analogy, to be 'useful' to us, in manipulating and exploring the world, and also to suggest ways to further refine the theories themselves. And of course not explicitly contradict some well-established observation.

So the 'problem' of whether a theory is ultimately 'true' we can safely leave to the philosophers. The simpler one, with equal explanatory power, is the one which will be more productive because it is easier to work with, why make it harder than necessary to make practical progress?

WTF is 'irrational' about this approach?

Your arguments do not have a rational basis either. I'm just admitting that mine don't. Your most important beliefs were formed instinctively and you've just tried to give it a rational structure to justify it.

Instinct is far better than reason in a civilized society. If we lose our instincts and have to rely on reason we'd be blind. Every direction would look the same. 

The fact that babies don't diffrentiate between opposing theories doesn't stop it being instinctive. Our instincts develop.

 Common sense is not Occam's razor. They just happen to give similar results. 

Well I didn't say that exactly, but the point is that I don't need an algorithm to asign probabilities. 

 Yes. I trust my instincts.

You've misunderstood me. I'm not trying to put forward a rational argument showing that occam's razor is untrue. I'm trying to show that occam's razor cannot be shown to be true (or probable) from a rational argument. 

You really have. I simply don't hold the views you are presenting as my own.

Now distinguish between 'truth' and 'Truth'. This is quite important, because if your 'truth' isn't reallt 'True', why should we care about it?

Well you're both wrong. 

Then your argument is clearly circular. You used examples of absurd things to show that occam's razor is untrue and you used occam's razor to show that the same things are absurd. 

I can agree that it's usually useful. I can't agree that you have any way of showing that arguments that make less assumptions are more likely to be true than similarly supported arguments that make more assumptions. That, you just feel to be true.