Plantinga Pwns, Part VI: The Evolutionary Argument Against Naturalism

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The work of Alvin Plantinga has not garnered much attention outside the world of philosophy.  I thought it worthwhile to spend some time on his work, so that readers could gain an appreciation for some of his arguments and realize the profound influence he has had on Christian philosophy.  While most of his work has not entered the general public's consciousness, one argument has gained the attention of the atheist community, and therefore their ire.  It is known as the Evolutionary Argument Against Naturalism.

While the argument has found serious consideration in the philosophy community, some of the reactions from the outside have been downright vitriolic.  It's a rather curious phenomenon.  Part of it has to do with the fact that Plantinga recently wrote his first popular-level book - Where the Conflict Really Lies, which has found a wider audience than his previous books.

First, we will cover the argument itself, then briefly discuss some of the reactions to it.

The Argument

The argument could be considered a particular version of the Argument from Reason.  In its most basic (and somewhat oversimplified) form, the Argument from Reason asks, as in the words of John Lennox, "If in the end my beliefs, my scientific theories, are the results - ultimately - of the motions of atoms in my brain, produced by an unguided, random, mindless process, why should I believe them?  In other words, it's like someone sitting on the branch of a tree cutting off the branch on which they're sitting."1  The argument was made famous by C.S. Lewis in chapter 3 of his book Miracles (one of my favorites); there are also allusions to the idea in the work of Chesterton, J.B.S Haldane, Darwin, and others.

Plantinga first came up with the EAAN in 1993, and has revised it several times since then.  It begins by defining naturalism as the view that there is no such person as God or anything similar.2  It should be noted that naturalism entails atheism, but atheism does not necessarily entail naturalism.  Naturalism is somewhat stronger due to its "or anything similar" clause mentioned by Plantinga above.  Technically an atheist could believe in some sort of impersonal supernatural force which transcends the laws of nature, while a naturalist could not.  In answer to the question of how our cognitive faculties came about, naturalists look to evolution for an answer.  This conjunction of naturalism and evolution creates a problem.

The problem arises from the fact that the goal of natural selection is the production of faculties which aid in the survival of a species, not the ascertainment of truth.  And if evolution is not guided by an intelligent being, then there is no guarantee of any beliefs that come about being true.  So the issue is the reliability of our cognitive faculties, given naturalism and evolution are true.  To put it in Bayesian notation, the problem is P(R|N&E) - the probability that our cognitive faculties are Reliable given the conjunction of Naturalism and Evolution.  Plantinga's claim is that the probability is either low or - at best - inscrutable.  This provides a defeater to the belief that both naturalism and evolution are true.  So, what Plantinga is doing is taking a widespread belief (or conjunction of beliefs) and turning it on its head.

To quote Plantinga, "The question of the value of P(R|N&E) really turns on the relationship between belief and behavior."3  There are several different theories to explain the nature of this relationship, and each has a slightly different take on the problem.  In epiphenomenalism, mental events - decisions, thoughts, memories - depend on physical events.  They may occur simultaneously, but the physical events occur logically prior to mental events.  Behavior is not caused by beliefs.  Beliefs are just along for the ride, as it were.  But if that is the case, then beliefs would be irrelevant to evolutionary processes, and therefore it seems P(R|N&E) is low.

There are two other options that run contrary to epiphenomenalism.  In the first, beliefs do result in certain behavior, but these behaviors are counterproductive- maladaptive.  It seems pretty obvious that in this case P(R|N&E) would be low.  Few - if any - people take such a position.  The more interesting option is that beliefs do result in behavior, and these behaviors are beneficial (this is the "common sense" view).  Plantinga would argue that in this case false beliefs could nonetheless come about.  "The reason is that if behavior is caused by belief, it is also caused by desire (and other factors - suspicion, doubt, approval, and disapproval - that we can here ignore).  For any given adaptive action, there will be many belief-desire combinations that could produce that action; and very many of those belief-desire combinations will be such that the belief involved is false."4

He gives a rather hilarious example as an illustration of how this could be so.  Say Paul - some primitive homo sapien - actually likes the idea of being eaten by a tiger, but he always runs away to look for a better prospect, because he does not think this tiger will actually eat him.  Or, in another example, Paul may think that the tiger is really cuddly, and he also thinks that the best way to cuddle with it is to run away from it as fast as is humanly possible.  In both cases, from a survival perspective Paul is doing great- he ran away and thus avoided being eaten.  But his beliefs are definitely false.

If I may summarize, I would say that for a given situation in which a conscious human might find herself, there is a very narrow range of beliefs that - in conjunction with some desire - would be basically true or very close to the truth.  And for that same situation there are a seemingly infinite possibilities of belief-desire combinations where the belief is far from the truth, or the complete opposite, or utterly ridiculous, and yet the belief-desire combination tends towards survival.  If the cognitive faculties of this human are to be reliable, they must hit the bulls-eye or come very close for every belief-forming situation.  But if the processes of evolution that lead to the belief-forming faculties is unguided and random, it seems the odds of landing on a true belief every time are low.

What if you are skeptical of all this?  What if you see Plantinga's point, but are unsure that we can say positively that the probability that our faculties are reliable is low?  Then agnosticism is a reasonable position; in such a case the probability is inscrutable.  So, either P(R|N&E) is low or it is inscrutable.

Here's the upshot: if the argument is right, then it seems that the reliability of our cognitive faculties is either low or inscrutable.  In other words, the argument "gives the naturalist-evolutionist a defeater5 for R."6  Now, in some instances it is possible to defeat a defeater - a defeater-defeater.  But in this case, a defeater-defeater would require an argument that involves another belief, and that belief will be subject to the original defeater.  So, the defeater for R is basically invincible.  This all means that the conjunction of naturalism and evolution is self-defeating.

Here's a final twist.  If naturalism is true, evolutionary almost certainly is as well.  When it comes to finding a naturalistic explanation for the existence of all the various species, evolution is really the only game in town.  And if that's the case, then naturalism by itself is self-defeating.


The EAAN has caused quite a stir, both in the philosophical community and outside it.  There's a book dedicated to the critiques of 11 philosophers, with Plantinga's responses.  Some of the critiques are very intriguing, and I won't be able to cover them.  Rather, I thought I'd cover some of the rebuttals that are clearly off-base, as a way of elaborating and clarifying the argument itself.  You will find that misunderstandings abound.

"The evolutionary argument against naturalism (EAAN), by Alvin Plantinga is perhaps the most original and tangled argument for God to have arose since the middle ages."7  I rather doubt the EAAN is an original and tangled argument for the existence of God primarily because it is not an argument for the existence of God.  It is an argument against naturalism; I thought that might be clear from the name.  It does not in any way seek to prove God exists.  If naturalism is defeated by the argument, that does not mean that super-naturalism wins by default.  An argument must be put forth for the existence of God for super-naturalism to succeed.  If the arguments for the existence of God fail, then the proper position to take is agnosticism.

Some object that the EAAN misses the point.  When it comes to the reliability of our cognitive faculties, we must look to empirical measurement - to science - to determine if our faculties or those of another species are reliable.  Some esoteric argument is irrelevant.  Unfortunately, it is this objection that misses the point.  Empirical measurements can only look at actions, and any beliefs and desires of subjects can only be reported by those subjects- they cannot be measured.  The inner workings of the mind are not directly measurable.  So even if the language and actions of a subject suggest they correctly understand a situation, the content of their beliefs may still be false.  But let us even grant that the argument has no say on the reliability of our cognitive faculties, and that the reliability of subjects can somehow be directly measured.  The results of the experiment presuppose that the cognitive faculties of the scientists is reliable.  If they were not, the experiment would not be able to get off the ground.

Another objection is that because the EAAN calls the reliability of our cognitive faculties into question, we should also call the EAAN into question because we rely on our faculties to understand the argument.  This is a simple misunderstanding of how an argument works.  The argument does not conclude that our faculties are unreliable.  It concludes that naturalism is false.  The argument is somewhat like a reductio ad absurdum.  The assumed premise is that N&E is true (or just N is true).  We also assume implicitly that our cognitive faculties are reliable, or this whole exercise couldn't go anywhere (nor any mental exercise).  Based on the assumed premise and through the course of the argument, we conclude that our cognitive faculties are not reliable.  But this contradicts one of our premises (that they are reliable), and therefore the assumed premise - that N&E (or just N) is true - must be false.

1.  The God Delusion Debate, October 3, 2007, at the Alys Stephens Centre, Birmingham, Alabama.  YouTube link to the debate.
2.  In other words, the argument uses a definition of metaphysical naturalism, as opposed to methodological naturalism.  Some objections to the argument do not take this into account; methodological naturalism is not relevant to the EAAN.
4.  Ibid., p. 9
5.  A defeater is a belief that either undercuts or opposes another belief
6.  Naturalism Defeated, p. 12
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1 comment :

  1. A pretty good summary! (Though, I think it would have been better to focus on Plantinga's more recent formation found in "Where the Conflict...")

    A minor complaint: you said

    "The argument does not conclude that our faculties are unreliable. It concludes that naturalism is false."

    But that isn't really accurate. The EAAN does not conclude that N is false. The conclusion is that the reflective N cannot rationally accept N&E.