The Evolutionary Argument Against Naturalism

The Evolutionary Argument Against Naturalism (EAAN) says that if both naturalism (the view that nothing supernatural exists) and evolution are true, we have strong reason to doubt our own minds - and therefore strong reason to doubt naturalism itself. The reasoning: evolution shaped our brains for survival, not truth, so a naturalist who accepts evolution should not trust the very thinking that produced her belief in naturalism. Alvin Plantinga first laid out the argument in his 1993 book Warrant and Proper Function and has refined it for three decades, making it one of the most discussed arguments in recent philosophy of religion. It scores 20/100 for soundness: the EAAN is a clever self-defeat argument that raises a real puzzle, but it rests on questionable assumptions about how evolution shapes cognition and ultimately fails to establish its central claim.

The Core Argument

Plantinga’s argument has a precise formal structure:

1. Let N = naturalism (no supernatural beings exist) and E = evolution (our cognitive faculties arose through natural selection and random genetic variation).
2. The probability that our cognitive faculties are reliable (R), given N&E, is low or impossible to estimate: P(R|N&E) is low or inscrutable.
3. If P(R|N&E) is low or inscrutable, then anyone who accepts both N and E has a defeater for R (a reason to doubt their own minds).
4. A defeater for R is a defeater for any belief produced by our minds - including the belief in N&E itself.
5. Therefore, N&E is self-defeating: accepting it gives you a reason to reject it.
6. Theism doesn’t face this problem, because on theism God designed our minds to be reliable.

The argument doesn’t claim evolution is false or that naturalists are irrational. It claims the combination of naturalism and evolution is internally incoherent - a consistent naturalist who accepts evolution should lose confidence in all her beliefs, including her naturalism.

Why Plantinga Thinks Evolution Cannot Guarantee Truth

Behavior vs. Belief

The central engine of the argument is that natural selection acts on behavior, not on the truth of beliefs. A gazelle that runs from a lion survives. But Plantinga argues that many different belief systems could produce the same fleeing behavior. Maybe the gazelle believes the lion is dangerous and runs away. Or maybe it believes the lion is a friendly creature and is running toward it by a roundabout route. Or maybe it wants to play tag. As long as the behavior is adaptive, selection doesn’t care about the underlying beliefs.

If beliefs are “invisible” to natural selection this way, there’s no evolutionary pressure specifically favoring true beliefs. The probability that our minds reliably produce true beliefs, given only naturalism and unguided evolution, would be no better than chance.

The Probability Claim

Plantinga argues P(R|N&E) - the probability our minds are reliable given naturalism and evolution - is either low or inscrutable (impossible to estimate). He considers several ways beliefs might relate to behavior under naturalism:

• Epiphenomenalism: Beliefs are byproducts of brain states with no effect on behavior. If so, selection can’t shape beliefs at all, and reliability is extremely unlikely.
• Semantic epiphenomenalism: Beliefs cause behavior through their physical brain properties, but their content (what they’re about) doesn’t matter causally. Selection shapes the brain hardware, but truth or falsity plays no role.
• Content-relevant causation: Beliefs cause behavior partly because of their content. Even here, Plantinga argues, false beliefs could produce adaptive behavior just as easily as true ones.

In each case, Plantinga concludes we have no grounds for trusting our minds.

Counterarguments and Rebuttals

Evolution Does Track Truth

The most powerful response is that Plantinga drastically underestimates the link between true beliefs and adaptive behavior. Philosophers like Elliot Sober and Branden Fitelson argue that in practice, the simplest and most reliable way for an organism to behave adaptively is to represent the environment accurately. Plantinga’s alternative scenarios - the gazelle that runs from lions because it finds them sexually attractive - are logically possible but biologically absurd. They require elaborate, jerry-rigged belief-desire systems that are far less likely to arise and far less robust across varied environments than simple truth-tracking systems.

Consider the evolutionary epistemology literature: organisms with more accurate perceptual systems consistently outcompete those with less accurate ones. The independent evolution of camera-type eyes across many lineages shows natural selection drives hard toward environmental accuracy. Evolution doesn’t produce perfect minds - our many cognitive biases prove that - but it reliably produces minds accurate enough to ground further reasoning.

The Bizarre Belief Scenarios Are Not Equiprobable

Plantinga treats his fanciful alternative belief systems as if they were just as likely as truth-tracking systems. But philosophers like James Beilby point out this ignores the huge space of possible false beliefs compared to the narrow set that would produce adaptive behavior. For any given adaptive behavior, there may be one or a few true belief-desire combinations that produce it, but the false combinations that happen to produce the same behavior are wildly specific and improbable. The chance of evolution stumbling onto a complex system of false beliefs that just happens to generate correct behavior across many environments is tiny compared to the chance of producing roughly true beliefs.

The Self-Defeat Problem Applies to Theism Too

If Plantinga’s skeptical argument is taken seriously, it threatens theistic belief too. How do we know God designed our minds for truth rather than for obedience, worship, or comfort? We’d need reliable minds to evaluate whether our minds were designed for truth - but that’s the very capacity in question. As philosopher Troy Nunley and others have argued, the EAAN creates a universal skepticism that doesn’t selectively spare theism.

Naturalism Can Be Confirmed Empirically

Even if Plantinga is right that P(R|N&E) is initially low, naturalists aren’t trapped. Naturalized epistemology, developed by W.V.O. Quine, holds that we can bootstrap our way to justified confidence in our minds through empirical testing. Science works by making predictions and checking them against observations. The spectacular success of science - landing rovers on Mars, predicting eclipses to the second, curing diseases - is strong evidence that our minds are reliable, regardless of the prior probability set by a philosophical argument. Plantinga’s prior probability calculation is overwhelmed by this real-world evidence.

Historical Background

Plantinga first sketched the EAAN in Chapter 12 of Warrant and Proper Function (1993), though the idea goes back much further. Charles Darwin himself expressed a version of the worry in an 1881 letter: “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.” C.S. Lewis made a related argument in Miracles (1947), arguing that naturalism undermines the rational foundations it needs to support itself.

Plantinga’s distinctive contribution was to formalize the argument using probability theory and embed it within his broader Reformed epistemology framework. He refined the argument in response to critics in Naturalism Defeated? (2002, edited by James Beilby), and again in Where the Conflict Really Lies (2011), where he argued that the real conflict in science and religion is not between theism and science but between naturalism and science.

Modern Developments

The EAAN continues to generate active debate in epistemology and philosophy of religion. Several developments are worth noting:

Bayesian reformulations. Philosophers have tried to formalize Plantinga’s probability claims using Bayesian epistemology. These formalizations have generally been unfavorable to the EAAN, showing that even modest links between true beliefs and adaptive behavior are enough to make P(R|N&E) reasonably high.

Evolutionary debunking arguments. The broader family of evolutionary debunking arguments - which use evolutionary origins to cast doubt on moral, mathematical, or religious beliefs - has grown a lot. Ironically, some are used against theism: if religious beliefs evolved because they were adaptive (promoting group cohesion and cooperation), that gives us reason to doubt their truth, not affirm it.

Cognitive science of religion. Research in the cognitive science of religion suggests humans are naturally wired to detect agency and purpose in the environment - a tendency called the “hyperactive agency detection device.” This cuts both ways: it explains why theistic beliefs are so common (they’re cognitively natural) but also suggests they may be products of cognitive biases rather than accurate perception of reality.

Reliabilism and proper function. Plantinga’s own proper function epistemology holds that beliefs are warranted when produced by minds functioning properly according to a design plan aimed at truth. Naturalists argue that evolution provides exactly such a design plan, making proper function epistemology compatible with naturalism despite Plantinga’s protests.

Relationship to Other Arguments

The EAAN is closely related to the Argument from Reason, which makes a broader case that naturalism undermines the reliability of rational thought. Where the EAAN focuses on the evolutionary origins of cognition, the Argument from Reason (following C.S. Lewis) targets the more general question of whether physical causation can ground rational inference. Both share the same basic strategy - arguing that naturalism is self-defeating - and face many of the same objections.

The Argument from Consciousness offers a complementary approach from a different angle. Rather than asking whether evolved minds can be reliable, it asks whether physical processes can produce conscious experience at all. Together, these three arguments form a cluster of challenges centered on the nature of mind.

The Moral Argument for God uses a parallel structure in ethics: if moral beliefs evolved for survival rather than tracking objective moral truth, then evolutionary naturalism undermines moral realism. All four arguments share the strategy of claiming naturalism can’t ground some important feature of our mental lives - reason, consciousness, morality, or cognitive reliability.

Critics often note that the Burden of Proof Argument applies forcefully here: the EAAN doesn’t provide positive evidence for God’s existence but tries to undermine naturalism, leaving theism as the last option standing. An argument that just weakens the competition, without providing its own evidence, is inherently limited. The Occam’s Razor principle also applies - invoking a supernatural designer to explain cognitive reliability adds complexity that requires justification.

Common Misconceptions

“The EAAN says evolution is false.” It doesn’t. Plantinga accepts evolution. The argument targets the combination of naturalism and evolution, claiming they are jointly self-defeating. Plantinga believes evolution is true but guided by God.

“The EAAN proves God exists.” The argument is defensive, not constructive. Even if fully successful, it would only show naturalism is self-defeating - it wouldn’t positively establish God’s existence. Other non-naturalist worldviews (panpsychism, idealism, neutral monism) would also escape the self-defeat charge.

“Plantinga claims we can’t trust science.” His claim is conditional: if naturalism is true, then we can’t trust our minds. He believes we can trust our minds because he believes theism (not naturalism) is true. The argument is an attack on naturalism, not on science or evolution.

Our Scoring

The soundness score of 20 reflects that the EAAN, while cleverly built, rests on a deeply questionable central premise - that natural selection cannot produce reliable minds. The argument’s fanciful scenarios of false beliefs producing adaptive behavior are logically possible but biologically implausible. Evolutionary epistemology gives strong reasons to think truth-tracking is the most efficient and robust cognitive strategy for surviving in complex environments, and the success of science is overwhelming real-world evidence that our minds are substantially reliable. The argument also faces a bootstrapping objection: its skeptical conclusion, if taken seriously, would undermine the very reasoning used to build the argument, creating a self-referential paradox. Most philosophers working in epistemology and philosophy of mind see the EAAN as interesting but ultimately unsuccessful.

The Creator score of 50 is the highest, tied with Higher Power, because the EAAN - if sound - most directly suggests our minds were designed for truth by an intelligent being. A designer who built minds to be reliable maps naturally onto a Creator concept. However, the argument doesn’t specify what kind of creator or provide evidence of specific creative acts, which limits the score.

The Higher Power score of 50 matches the Creator score because the argument equally supports a vaguer idea of some rational principle or consciousness behind reality that ensures our minds can track truth. A Higher Power that grounds the rational order of the universe would meet the argument’s requirements without needing to be a personal being with specific attributes.

The Personal God score of 45 is slightly lower because the EAAN, even if sound, establishes only that something designed our minds for reliability - not that this designer is all-knowing, all-good, or personally invested in human affairs. The gap between “a rational designer ensured cognitive reliability” and “the God of classical theism who hears prayers and intervenes in history” is large. Plantinga himself bridges this gap through his broader Reformed epistemology, but the EAAN alone doesn’t provide the resources to do so. The score is still moderate because a personal God who cares about a truthful relationship with humans would have strong motivation to give us reliable minds.