Refuting Presuppositionalism

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Refuting Presuppositionalism


Presuppositionalism is one of the strangest, and indeed, one of the most difficult-to-understand approaches to defending the existence of God. The basic idea is that you cannot believe that something (i.e. the uniformity of nature or the reliability of your mind) unless you presuppose the existence of God. The reasoning behind all of this is very peculiar and seldom clearly stated by its proponents.

Are the Laws of Logic Proof of God?

Matt Slick, a well-known supporter of Presuppositionalism, has attempted to break down the line of reasoning behind his form of Presuppositionalism (The Transcendental Argument for the Existence of God, hereafter known as TAG). I think Slick has simplified it about as well as can be done, although I feel he ought to have put it into a standard syllogistic form. I’m going to attempt to do this, as I feel it will make it much easier for us to understand where the argument goes wrong.

Allow me to define some terms before I begin: I’m going to use LA to stand for “logical absolute” by which I mean the Law of non-contradiction (actual contradictions cannot be true), the law of identity (things are what they are and they are not what they are not), the law of excluded middle (something cannot be both true and not true), Etc. By “conceptual” I mean a mental representation of an actual or possible thing. Here is the series of syllogisms which comprise the TAG:

1. LAs do not arise from matter, motion, time, space, etc.
2. Something that does not arise from matter/motion/time/space/etc. is not physical (by definition).
3. Anything that is not physical is conceptual.
4. Therefore, from 1-3, LAs are conceptual.

1. Conceptual Things depend on a mind to exist.
2. LAs are conceptual.
3. Therefore, LAs depend upon a mind to exist.
4. LAs exist.
5. Therefore, one or more mind must be authoring LAs (follows from 1-4).

1. LAs are authored by a mind.
2. Minds are either perfect or they are not.
3. LAs are not authored by a non-perfect mind or mind. Follows from the principle of sufficient reason: A cause cannot be greater than its effect, so a concept could not be more perfect than the mind creating it. Since human minds are universally imperfect, human minds could not create LAs, which are completely perfect.
4. Therefore, LAs are authored by a perfect mind.

1. LAs are authored by an absolute mind.
2. Minds must exist to author concepts.
3. Therefore, the absolute mind authoring LAs exists.

Questionable Premises of TAG

The first questionable premise is A (1). Logical absolutes do not “arise from” physical things, rather logical absolutes are expressed by physical things because everything (whether possible or actual) must follow logical absolutes (for example, all possible or actual things must be what they are and cannot be what they are not). In fact, for something to even be considered “possible” it must, by definition, be in accord with the laws of logic (it must be what it is and not what it is not).
The second questionable premise is A (3). Just because something is not physical does not automatically mean that it is conceptual. Perhaps logical absolutes constitute a category in and of themselves and are not part of the categories of ‘conceptual things’ or ‘physical things’. They aren’t physical. And they are not conceptual: something that is conceptual is a mental representation of an actual or possible thing. But the mental representation of, for example, the law of non-contradiction, is not identical with the law of non-contradiction itself. The law of non-contradiction is an objectively true statement that applies to all possible or actual states of affairs.

A Strange Similarity

While I was thinking about TAG, I noticed that it had a striking resemblance to another argument I had once heard. Alvin Plantingaput it this way:

“[It] seems plausible to think of numbers as dependent upon or even constituted by intellectual activity; indeed, students always seem to think of them as "ideas" or "concepts", as dependent, somehow, upon our intellectual activity. So if there were no minds, there would be no numbers.”

Plantinga goes on to talk about how all numbers are probably not due to human intellectual activity, and so Plantinga draws the conclusion that they must be due to some higher intellectual activity (i.e. God’s intellectual activity) therefore God exists.
This argument is wrong for reasons similar to the reasons that TAG is wrong: It confuses the mental representations of numbers with numbers themselves. Numbers are simply amounts of some type of thing. And the amount of some type of thing is not the same as our mental representation of the amount of that thing. So numbers are fundamentally not conceptual, and since they are not conceptual, we do not need to account for them with a mind. If we do not need to account for them with a mind, then we do not need to account for them with God’s mind.

The Argument from the Uniformity of Nature

Dr. Jason Lisle of Answers in Genesis summed up the argument this way:
1. Science requires uniformity.
2. Uniformity requires a biblical worldview.
3. Therefore, science requires a biblical worldview.
The first premise is definitely true, although I wonder how creationists think they can advocate the uniformity of nature while simultaneously proposing that the rates of radiometric decay were super-fast in the past (to explain away radiometric dates).
The entire argument really hangs on the second premise: Uniformity requires a biblical worldview. The reasoning Lisle offers in support of this is:

“The Christian worldview gives us a reason to expect uniformity: a God who is beyond time, who upholds the universe in a consistent fashion, and who has told us so.”

How would a God beyond time give us reason to expect uniformity? I suppose that Lisle might be thinking that since physical laws are changeless they must have come from something changeless (like a changeless God). But what about all the things that God allegedly made which can change? Did changing things come from a changeless God? If so, then it seems that there is no reason to expect uniformity on the basis that there exists a timeless God.

Besides, I would claim that one can be completely justified in believing the uniformity of nature without reference to a Creator. Ask yourself: Is uniformity simpler than variety? Is it simpler for things to behave the same way throughout all time rather than behaving several different ways over the course of time? It certainly is, and since Occam’s razor tells us that “the simplest explanation is most probably correct” then it follows that certain regularities in the behavior of matter that we observe today were very probably the same in the past, and very probably will be the same in the future.
This brings us to another question: atheists and agnostics may be justified in believing that nature is uniform because of their experience, but wouldn’t it still be true that theists have a reason to expect a uniform universe in advance while atheists do not? Perhaps so, but then again there is no more reason to presuppose that a consistent God exists (prior to examining the real world) than there is to suppose that a consistent universe exists (prior to examining the universe).
Lisle’s third point, that he has reason to expect a uniform universe because God told him so, is simply ridiculous. The men who wrote the Bible would have been perfectly aware that the universe exhibits some regularity (as all people are) and so sticking such a thing in there is not really a sign of divine inspiration.

Bertrand Russell mentions further problems with Lisle’s argument:

“[W]here you can get down to any knowledge of what atoms actually do, you will find they are much less subject to law than people thought, and that the laws at which you arrive are statistical averages of just the sort that would emerge from chance. There is, as we all know, a law that if you throw dice you will get double sixes only about once in thirty-six times, and we do not regard that as evidence that the fall of the dice is regulated by design; on the contrary, if the double sixes came every time we should think that there was design. The laws of nature are of that sort as regards a great many of them. They are statistical averages such as would emerge from the laws of chance; and that makes this whole business of natural law much less impressive than it formerly was.”

Must We Presuppose the Existence of God Before We Can Trust Our Own Thoughts?

C.S. Lewis once asked, “If thought is the undesigned and irrelevant product of cerebral motions, what reason have we to trust it?” Well, perhaps because the process of natural selection has, in a sense, ‘designed’ our brain and nervous system to give us accurate information about the world.
Alvin Plantinga has attempted to resuscitate this argument by arguing that unguided evolution probably will not produce a reliable brain. Plantinga says,

“Perhaps Paul [a prehistoric hominid] very much likes the idea of being eaten, but when he sees a tiger, always runs off looking for a better prospect, because he thinks it unlikely the tiger he sees will eat him. This will get his body parts in the right place so far as survival is concerned, without involving much by way of true belief. ... Or perhaps he thinks the tiger is a large, friendly, cuddly pussycat and wants to pet it; but he also believes that the best way to pet it is to run away from it. ... Clearly there are any number of belief-cum-desire systems that equally fit a given bit of behaviour.”[i]

But wouldn’t natural selection favor reliable and accurate memory? Does accurate memory not increase an organism’s chances of survival? Wouldn’t our prehistoric hominid Paul eventually realize that running away from the tiger is not the best way to pet it (since he could remember how things turned out the last time he ran away from the tiger)? A plethora of other problems exist which completely undermine the plausibility of Plantinga’s argument, which I do not see the need to go into here, since they’ve been covered elsewhere.[ii]


Presuppositionalist arguments are often difficult to refute on the spot if you’ve never heard them before. Chances are you haven’t heard them before, because Presuppositionalism represents a minority view that has only recently made a splash on the scene of Christian apologetics. I suspect that Christians are now using these arguments precisely because of their obscurity: the rarity and complexity of these arguments are such that many atheists won’t be able to respond to these arguments immediately, whereas more traditional arguments like the first cause argument and the argument from design are arguments that practically every atheist can immediately tear down (because atheists have heard these arguments used so much). However, once presuppositionalist arguments are carefully examined, they can quickly be shown to be fallacious and invalid. So my advice to fellow atheists and agnostics who frequently argue with Christians is this: be familiar with these arguments and be prepared to expose the errors in them whenever you hear them. Chances are that sooner or later you will come across someone in person or on the internet who uses these arguments. Please take my advice and arm yourself in advance.


[i] Alvin Plantinga, Warrant and Proper Function, (New York: Oxford University Press, 1993), pp.225-226.

[ii] See Stephen Law, "Plantinga's Belief-Cum-Desire Argument Refuted" forthcoming in "Religious Studies". Also: Paul Draper "In Defense of Sensible Naturalism"

And Section III.9 of Sense & Goodness Without God: A Defense of Metaphysical Naturalismby Richard Carrier.