The evolutionary argument against naturalism (EAAN) is a philosophical argument asserting a problem with believing both evolution and philosophical naturalism simultaneously. The argument was first formally proposed by Alvin Plantinga in 1993. The EAAN argues that the combined belief in both evolutionary theory and naturalism is epistemically self-defeating. The argument states that if both evolution and naturalism are true, then the probability of having reliable cognitive faculties is low, which then destroys any reason to believe in evolution or naturalism in the first place, as the cognitive faculties one used to deduce evolution or naturalism as logically valid are no longer reliable. The argument "raises issues of interest to epistemologists, philosophers of mind, evolutionary biologists, and philosophers of religion".Beilby(2002) p vii It comes as an expansion of the argument from reason, although the two are separate philosophical arguments.
Development of the idea The idea that "naturalism" undercuts its own justification was put forward by Arthur Balfour.Victor Reppert, C.S. Lewis's Dangerous Idea, In Defense of the Argument from Reason (2003) p 46 C. S. Lewis popularised it in the first edition of his book Miracles in 1947. Similar arguments were advanced by Richard Clyde Taylor in Metaphysics,Beilby(2002) p ix as well as by Stephen Clark,Arthur Balfour, The Foundations of Belief: Notes Introductory to the Study of Theology, 8th ed. Rev. with a new introduction and summary (1906) pp 279–285 Richard PurtillRichard Purtill, Reasons to Believe (1974) pp 44–46 and J. P. Moreland.J. P. Moreland, "God and the Argument from Mind", in Scaling the Secular City (1978) pp 77–105 In 2003 Victor Reppert developed a similar argument in detail in his book C.S. Lewis's Dangerous Idea, In Defense of the Argument from Reason. Contemporary philosophers who have employed a similar argument against physical determinism are James Jordan and William Hasker.Victor Reppert, C.S. Lewis's Dangerous Idea, In Defense of the Argument from Reason (2003) pp 204–275
Plantinga proposed his "evolutionary argument against naturalism" in 1993. In the twelfth chapter of his book Warrant and Proper Function, Plantinga developed Lewis' idea, and constructed two formal arguments against evolutionary naturalism. He further developed the idea in an unpublished manuscript entitled "Naturalism Defeated" and in his 2000 book Warranted Christian Belief, and expanded the idea in Naturalism Defeated?, a 2002 anthology edited by James Beilby. He also responded to several objections to the argument in his essay "Reply to Beilby's Cohorts" in Beilby's anthology.Beilby(2002) p 2
In the 2008 publication Knowledge of God Plantinga presented a formulation of the argument that solely focused on semantic epiphenomenalism instead of the former four jointly exhaustive categories.Alvin Plantinga, Michael Tooley, Knowledge of God (2008) pp 31–51
Plantinga repeats the argument in his 2011 book Where the Conflict Really Lies: Science, Religion, and Naturalism.
Plantinga's 1993 formulation of the argument Plantinga argues that combining naturalism and evolution is self-defeating, because, under these assumptions, the probability that humans have reliable cognitive faculties is low or inscrutable. He claimed that several thinkers, including C. S. Lewis, had seen that evolutionary naturalism seemed to lead to a deep and pervasive skepticism and to the conclusion that our unreliable cognitive or belief-producing faculties cannot be trusted to produce more true beliefs than false beliefs. He claimed that "Darwin himself had worries along these lines" and quoted from an 1881 letter:Beilby p 3
In the letter, Darwin had expressed agreement with William Graham's claim that natural laws implied purpose and the belief that the universe was "not the result of chance", but again showed his doubts about such beliefs and left the matter as insoluble. Darwin only had this doubt about questions beyond the scope of science, and thought science was well within the scope of an evolved mind. Michael Ruse said that by presenting it as "Darwin's doubt" that evolutionary naturalism is self-defeating, Plantinga failed to note that Darwin at once excused himself from philosophical matters he did not feel competent to consider. Others, such as Evan Fales, agreed that this citation allowed Plantinga to call the source of the problem EAAN addresses Darwin's Doubt.Beilby p 46 Also, contrary to Ruse's claim, Plantinga gave the name "Darwin's Doubt" not to the idea that the conjunction of naturalism and evolution is self-defeating, but rather to the view that given naturalism and evolution our cognitive faculties are unlikely to be reliable. Plantinga asserts that "this doubt arises for naturalists or atheists, but not for those who believe in God. That is because if God has created us in his image, then even if he fashioned us by some evolutionary means, he would presumably want us to resemble him in being able to know; but then most of what we believe might be true even if our minds have developed from those of the lower animals."
Plantinga defined: N as naturalism, which he defined as "the idea that there is no such person as God or anything like God; we might think of it as high-octane atheism or perhaps atheism-plus." E as the belief that human beings have evolved in conformity with current evolutionary theory R as the proposition that our faculties are "reliable", where, roughly, a cognitive faculty is "reliable" if the great bulk of its deliverances are true. He specifically cited the example of a thermometer stuck at placed in an environment which happened to be at 72 °F as an example of something that is not "reliable" in this sense
and suggested that the conditional probability of R given N and E, or P(R|N&E), is low or inscrutable.
Plantinga's argument began with the observation that our beliefs can only have evolutionary consequences if they affect behaviour. To put this another way, natural selection does not directly select for true beliefs, but rather for advantageous behaviours. Plantinga distinguished the various theories of mind-body interaction into four jointly exhaustive categories:
epiphenomenalism, where behaviour is not caused by beliefs. "if this way of thinking is right, beliefs would be invisible to evolution" so P(R|N&E) would be low or inscrutableBeilby(2002) p 6 Semantic epiphenomenalism, where beliefs have a causative link to behaviour but not by virtue of their semantic content. Under this theory, a belief would be some form of long-term neuronal event.Beilby(2002) pp 6–7. Here Plantinga cites Robert Cummins as suggesting that this is the "received view" However, on this view P(R|N&E) would be low because the semantic content of beliefs would be invisible to natural selection, and it is semantic content that determines truth-value. Beliefs are causally efficacious with respect to behaviour, but maladaptive, in which case P(R|N&E) would be low, as R would be selected against. Beliefs are causally efficacious with respect to behaviour and also adaptive, but they may still be false. Since behaviour is caused by both belief and desire, and desire can lead to false belief, natural selection would have no reason for selecting true but non-adaptive beliefs over false but adaptive beliefs. Thus P(R|N&E) in this case would also be low.Beilby(2002) pp 8–9 Plantinga pointed out that innumerable belief-desire pairs could account for a given behaviour; for example, that of a prehistoric hominid fleeing a tiger: Perhaps Paul 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.
Thus, Plantinga argued, the probability that our minds are reliable under a conjunction of philosophical naturalism and naturalistic evolution is low or inscrutable. Therefore, to assert that naturalistic evolution is true also asserts that one has a low or unknown probability of being right. This, Plantinga argued, epistemically defeats the belief that naturalistic evolution is true and that ascribing truth to naturalism and evolution is internally dubious or inconsistent.Beilby p 1
Responses
Fitelson and Sober's response In a 1998 paper Branden Fitelson of the University of California, Berkeley and Elliott Sober of the University of Wisconsin–Madison set out to show that the arguments presented by Plantinga contain serious errors. Plantinga construed evolutionary naturalism as the conjunction of the idea that human cognitive faculties arose through evolutionary mechanisms, and naturalism which he equated to atheism. Plantinga tried to throw doubt on this conjunction with a preliminary argument that the conjunction is probably false, and a main argument that it is self-defeating; if you believe it you should stop believing it.
First, they criticised Plantinga's use of a Bayesian framework in which he arbitrarily assigned initial probabilities without empirical evidence, predetermining the outcome in favor of traditional theism, and described this as a recipe for replacing any non-deterministic theory in the natural sciences, so that for example a probable outcome predicted by quantum mechanics would be seen as the outcome of God's will. Plantinga's use of R to mean that "the great bulk" of our beliefs are true fails to deal with the cumulative effect of adding beliefs which have variable reliability about different subjects. Plantinga asserted that the traditional theist believes being made in God's image includes a reflection of divine powers as a knower, but cognitive science finds human reasoning subject to biases and systematic error. Traditional theology is not shown to predict this varying reliability as well as science, and there is the theological problem of the omnipotent Creator producing such imperfection. They described how Plantinga set out various scenarios of belief affecting evolutionary success, but undercut the low probability he previously required when he suggested an "inscrutable" probability, and by ignoring availability of variants he fails to show that false beliefs will be equally adaptive as his claim of low probability assumes. Even if his claims of improbability were correct, that need not affect belief in evolution, and they considered it would be more sensible to accept that evolutionary processes sometimes have improbable outcomes.