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The Evolutionary argument against naturalism (sometimes abbreviated EAAN) is a philosophical argument that metaphysical naturalism when combined with contemporary evolutionary accounts of the origin of human life is self-defeating. Although C. S. Lewis made somewhat similar observations, the argument as it is commonly presented was first put forward and has mostly been developed by Alvin Plantinga, a contemporary philosopher of religion and epistemology at the University of Notre Dame.

EAAN is considered by by Barbara Forrest and Paul R. Gross to be part of the intelligent design movement's attack on naturalism. Plantinga and Beilby made clear that EAAN is not directed against the theory of evolution.

C. S. Lewis

The general claim that naturalism undercuts its own justification was argued by C. S. Lewis in the third chapter of his book Miracles. Given that "no thought is valid if it can be fully explained as the result of irrational causes," and assuming that evolution is one such cause ("every theory of the universe which makes the human mind as a result of irrational causes is inadmissible, Naturalism, as commonly held, is precisely a theory of this sort"), Lewis concludes that if evolution did give rise to our cognitive faculties, then our thoughts and perceptions would be "the results of irrational causes," which would render them unreliable. Thus the naturalist incurs a logical self-contradiction. This argument is only vaguely similar to Plantinga's, of which it should not be taken as a summary or even a primordial version.

Lewis argued along similar lines in numerous other writings. For instance, in "On Living in an Atomic Age" he claimed that “It is only through trusting our own minds that we have come to know Nature herself. If Nature, when fully known, seems to teach us (that is, if the sciences teach us) that our own minds are chance arrangements of atoms, then the sciences themselves would be chance arrangements of atoms and we should have no reason for believing them.”

Plantinga's Argument

Plantinga's argument attempts to show that to combine naturalism and evolution is self-defeating, because, under these assumptions, the probability that humans have reliable cognitive faculties is low or inscrutable. The full version of the argument was first published in Warrant and Proper Function (1993). It also appears, in reduced form, in the entry on Religion and Science of the Stanford Encyclopedia of Philosophy. A more recent and extensive discussion is found in Naturalism Defeated? (2002), an anthology edited by James K. Beilby, in which Plantinga presents a slightly modified form of the argument, 11 philosophers respond, and Plantinga attempts to rebut their objections.

Plantinga traces his meditations all the way back to Charles Darwin:

With me, the horrid doubt always arises whether the convictions of man's mind, which has been developed from the mind of the lower animals, are of any value or at all trustworthy. Would anyone trust in the convictions of a monkey's mind...?

— Charles Darwin.

Plantinga defines:

• N as naturalism
• E as the belief that we 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 cites a thermometer stuck at 72 degrees placed in an environment which happened to be at 72 degrees as an example of something that is not "reliable" in this sense

and suggests that the conditional probability of R given N and E, or P(R|N&E), is low.

Plantinga's argument begins 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 distinguishes the various theories of mind-body interaction into four jointly exhaustive categories:

1. 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 inscrutable
2. 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. 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.
3. 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.
4. 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. Plantinga points 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 argues, the probability that our minds are reliable under a conjunction of philosophical naturalism and 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 argues, epistemically defeats the belief that naturalistic evolution is true and that ascribing truth to naturalism and evolution is internally dubious or inconsistent.

It must be noted that Plantinga makes it clear he is not attacking the theory of evolution, which only yields the dreaded self-contradiction when connected with philosophical naturalism but is not equally inconsistent with theism. Theism may accept the scientific description of evolutionary processes but also allow for the presence of a God capable of creating a universe whose physical properties produce reliable human cognitive faculties, even though the direct physical cause thereof is undirected (see, for example, the philosophical position known as theistic evolution).

Responses by critics

Fitelson and Sober (1998)

Branden Fitelson of the University of California, Berkeley and Elliott Sober of the University of Wisconsin-Madison criticised the argument in 1998. They attack Plantinga on a number of points. First they criticise his use of a Bayesian framework, suggesting that it would apply equally well to "any non-deterministic theory in the natural sciences." Then they criticise Plantinga's presentation of the mechanisms of evolution and his analysis of the relation between belief and behavior: even though Plantinga may be correct that natural selection only "cares" about behaviour and not about the truth or falsity of beliefs, it still does not follow that true and false beliefs are equally likely to evolve.

Finally, they suggest that Plantinga does not show that proponents of metaphysical naturalism should a priori doubt all of their beliefs. This is because the argument rests in part on the idea that E&N together defeat proposition R (i.e., that evolution combined with philosophical naturalism make it unlikely that the great bulk of our beliefs are true). From this defeater Plantinga concludes that proponents of E&N should not have confidence in any of their beliefs, including their belief in E&N. But "ven if E&N defeats the claim that 'at least 90% of our beliefs are true,' it does not follow that E&N also defeats the more modest claim that 'at least 50% of our beliefs are true'." In other words, according to Fitelson and Sober, Plantinga needs to show not only that our beliefs could be false but adaptive, but that they could be pervasively so.

Robbins (1994) and Fales (1996)

Indiana University South Bend Professor of Philosophy J. Wesley Robbins contends that Plantinga's argument applies only to Cartesian philosophy of minds but not to pragmatist philosophies of mind. Robbins' argument, stated roughly, is that while in a Cartesian mind beliefs can be identified with no reference to the environmental factors that caused them, in a pragmatic mind they are identifiable only with reference to those factors. That is to say, in a pragmatic mind beliefs would not even exist if their holder had not come in contact with external belief-producing phenomena in the first place.

Philosopher of science Evan Fales argues along the same lines. Take a mental representation, of heat, for example. Only so long as it is really caused by heat can we call it a mental representation of heat; otherwise, it is not at all a mental representation, of heat or of anything else: "so long as representations are causally linked to the world via the syntactic structures in the brain to which they correspond , this will guarantee that syntax maps onto semantics in a generally truth-preserving way." This is a direct response to one of Plantinga's scenarios where, according to Plantinga, false-belief generating mechanisms may have been naturally selected.

Naturalism Defeated? (2002)

The volume, edited by James K. Beilby, contains responses by 11 philosophers to EAAN..

• William Ramsey argues that Plantinga “overlooks the most sensible way . . . to get clear on how truth can be a property of beliefs that bestows an advantage on cognitive systems”. He also argues the commonsensical point that since some of our cognitive faculties are slightly unreliable, isn't E&N better suited than theism to explain this imperfection?
• Jerry Fodor argues that there is a plausible historical scenario according to which our minds were selected because their cognitive mechanisms produced, by and large, adaptive true beliefs.
• Evan Fales argues that Plantinga has not demonstrated that the reliability of our cognitive faculties is improbable, given Neo-Darwinism, and emphasizes that “if Plantinga’s argument fails here, then he will not have shown that is probabilistically incoherent.” Also, given how expensive (in biological terms) our brain is, and considering we are rather unremarkable creatures apart from our brains, it would be quite improbable that our rational faculties be selected if unreliable. "Most of our eggs are in that basket," says Fales.
• Michael Bergmann suggests that Thomas Reid offers the resources for a commonsense (Reidian) defense of naturalism against EAAN.
• Ernest Sosa draws on features of Descartes’ epistemology to argue that while “ssues of circularity do arise as to how we can rationally and knowledgeably adopt view about our own epistemic powers,” nonetheless, “these problems are not exclusive to naturalism.”
• James Van Cleve suggests that even if the probability thesis is true, this need not deliver an undefeated defeater to R, and that even if one has a defeater for R, why does it follow that one has a defeater for everything?
• Richard Otte thinks the argument “ignores other information we have that would make R likely.”
• William Talbott suggests that “Plantinga has misunderstood the role of undercutting defeaters in reasoning.”
• Trenton Merricks says that “in general, inferences from low or inscrutable conditional probability to defeat are unjustified.”
• William Alston argues that the claim that P(R/N&E) is low is poorly supported; if, instead, it is inscrutable, this has no clear relevance to the claim that (1) is a defeater for N&E.

Plantinga's replies

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Naturalism Defeated? also included Plantinga's replies to both the critical responses contained in the book and to some objections raised by others, including Fitelson & Sober:

• Plantinga expounds the notion of Rationality Defeaters in terms of his theory of warrant and proper function and distinguishes between Humean Defeaters and Purely Alethic Defeaters, suggesting that although a Naturalist will continue to assume R "but (if he reflects on the matter) he will also think, sadly enough, that what he can't help believing is unlikely to be true."
• Plantinga argues that semantic epiphenomenalism is very likely on N&E because, if materialism is true, beliefs would have to be neurophysiological events whose propositional content cannot plausibly enter the causal chain. He also suggests that the reliability of a cognitive process requires the truth of a substantial proportion of the beliefs it produces, and that a process which delivered beliefs whose probability of truth was in the neighbourhood of 0.5 would have a vanishingly unlikely chance of producing (say) 1000 beliefs 75% of which were true.
• In The conditionalisation problem, Plantinga discusses the possibility that N i.e. "Naturalism plus R," could be a basic belief thus staving off defeat of R, suggesting that this procedure cannot be right in general otherwise every defeater could automatically be defeated, introducing the term "defeater-deflector " and initially exploring the conditions under which a defeater-deflector can be valid.

See also

• Problem of mental causation

Notes

1. Alvin Plantinga in Beilby(2002) p p
2. Intelligent Design Creationism and Its Critics, Chapter 5
3. Beilby(2002) p1
4. C.S. Lewis, Miracles, 1947, p. 26-7
5. Plantinga, Alvin. Warrant and Proper Function. New York: Oxford University Press, 1993. Print ISBN-10: 0-19-507864-0 Print ISBN-13: 978-0-19-507864-0 <http://dx.doi.org/10.1093/0195078640.001.0001>
6. Letter to William Graham, Down, July 3, 1881. In The Life and Letters of Charles Darwin Including an Autobiographical Chapter, ed. Francis Darwin (London: John Murray, Albermarle Street, 1887), Volume 1, pp. 315-316.
7. Beilby(2002) p 2.
8. Beilby(2002) p 6
9. Beilby(2002) pp 6-7. Here Plantinga cites Robert Cummins as suggesting that this is the "received view"
10. Beilby(2002) pp8-9
11. Plantinga, Warrant and Proper Function, pp. 225-226 <http://dx.doi.org/10.1093/0195078640.001.0001>
12. Beilby(2002) p1
13. Fitelson, Branden (1998). "Plantinga's Probability Arguments Against Evolutionary Naturalism" (PDF). Pacific Philosophical Quarterly. 79 (2): 115–129. doi:10.1111/1468-0114.00053. Retrieved 2007-03-06. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |quotes= ignored (help)
14. J. Wesley Robbins, "Is Naturalism Irrational?" in Faith and Philosophy, Vol. 11, No. 2, April 1994, pp. 255-259).
15. Evan Fales, "Plantinga’s Case against Naturalistic Epistemology," in Philosophy of Science 63, no. 3 (1996): 432-451.
16. Summarised, unless otherwised referenced, from the review by John F Post
17. Beilby(2002) p 211
18. Beilby(2002) pp211-213 - he says that these arguments are "related in ways that are not entirely clear to arguments made by Jaegwon Kim in Mind in a Physical World
19. ie something that prevents D (a supposed Defeater) from being a defeater in the first place, as opposed to a defeater-defeater which defeats D Beilby(2002) p224.

References

• Beilby, James K. (ed) (April 2002). Naturalism Defeated?: Essays on Plantinga's Evolutionary Argument Against Naturalism. Cornell University Press. p. 283 pages. ISBN 0801487633. {{cite book}}: |first= has generic name (help); Cite has empty unknown parameter: |coauthors= (help)

External links

• Plantinga's paper: "Naturalism Defeated" (pdf)
• Naturalism Defeated? reviewed by John F. Post at Notre Dame Philosophical Reviews
• Evil and Evolution (The Great Debate) a debate between philosopher Paul Draper, who was one of the first to argue that the cruelty and suffering in evolution is not compatible with theism, and Alvin Plantinga, who responds that evolution is rather in conflict with naturalism based on the argument in this article.

• Misplaced Pages articles that are too technical from January 2008
• Philosophical arguments
• Epistemology
• Philosophy of religion
• Naturalism