Can Atheism Trust the Mind? The Argument from Reason

The Question

Can a Blind Universe Trust the Mind?

• We use reason to figure out what is true, including big claims about reality.
• But what if every thought is just the product of physics and natural selection?
• Could a process aimed only at survival also be trusted to aim at truth?
• The Argument from Reason presses exactly this worry about naturalism.

The worry: It asks whether naturalism can justify the very reasoning used to defend it.

Key Terms

Naturalism and Two Kinds of Cause

• Naturalism, here, is the view that physical nature is all there is.
• On it, every belief has a purely physical cause — ultimately blind matter in motion.
• A ‘rational’ cause is one where a belief is held because of good reasons.
• A ‘non-rational’ cause, like a neuron firing, need not track truth at all.

The Argument

Lewis States the Case

• C. S. Lewis argued that naturalism has a self-undermining tendency.
• If reasoning is only the by-product of non-rational causes, its conclusions carry no rational authority.
• That would include the reasoning by which someone concludes naturalism is true.
• So, Lewis said, naturalism quietly saws off the branch it sits on.

Self-undermining: The charge is that naturalism cannot vouch for the mind that argues for it.

Source: C. S. Lewis, Miracles (1947), ch. 3

The Argument

Plantinga Sharpens It

• Alvin Plantinga recast the worry in terms of probability.
• Ask: given naturalism and evolution, how likely is it that our faculties are reliable?
• He argues that probability is low or inscrutable — written P(R | N&E).
• If so, you inherit a defeater for all your beliefs, naturalism included.

Where it’s argued: Plantinga’s Evolutionary Argument Against Naturalism appears in Warrant and Proper Function.

Source: Alvin Plantinga, Warrant and Proper Function (1993), ch. 12

Why Think It?

Survival, Not Truth

• Natural selection preserves behavior that helps an organism survive and reproduce.
• It rewards useful action, and a false belief can prompt useful action just as well.
• If a belief’s content doesn’t drive behavior directly, truth may be invisible to selection.
• This ‘semantic’ worry is the engine behind Plantinga’s low probability estimate.

The gap: Selection can see what you do, the objection says, but not what your belief means.

The Objections

The Naturalist Replies — At Full Strength

• Many able philosophers judge the argument unsound, and their case is strong.
• True beliefs generally guide action better than false ones, so selection should favor them.
• Daniel Dennett argues that true belief usually pays, with adaptive errors the rare exception.
• Jerry Fodor adds that fitness also depends on which variations are even available to selection.

Widely contested: The Argument from Reason is disputed; many naturalists find the replies decisive.

Source: Daniel Dennett & Alvin Plantinga, Science and Religion: Are They Compatible? (2011)

The Objections

Content, Behavior, and Anscombe

• Critics argue that belief content and behavior are linked, so tracking one tends to track the other.
• If so, selection for successful action would, over time, favor true belief.
• Elizabeth Anscombe’s 1948 critique also pressed Lewis on his key terms.
• She distinguished ‘non-rational’ from ‘irrational,’ prompting him to rewrite the chapter.

The Anscombe debate: After her 1948 Socratic Club paper, Lewis revised the third chapter of Miracles.

Source: G. E. M. Anscombe, ‘A Reply to Mr C. S. Lewis’ (Socratic Club, 1948)

The Replies

The Argument Answers Back

• Defenders reply that ‘usually adaptive’ is not the same as ‘reliably truth-tracking.’
• A firm content–behavior link, they say, is exactly what naturalism struggles to guarantee.
• The worry targets our high-level theorizing, not quick survival reflexes.
• Whether the reply succeeds is still genuinely disputed among philosophers.

An open question: Both sides have serious defenders; this is a live debate, not a settled rout.

Honest Limits

What It Can and Can’t Show

• At most, the argument concludes that reason needs grounding beyond blind matter.
• That is a long way from the full Christian God of the creeds.
• It might point toward theism, or some mind behind the cosmos, but no further on its own.
• Plantinga presents it as a defeater for naturalism, not a proof of Christianity.

Modest conclusion: Even if sound, it unsettles naturalism — it does not by itself establish theism.

Clearing It Up

It Is Not an Insult

• The argument does not claim that atheists are bad at reasoning.
• Plainly, naturalists reason brilliantly, and the argument assumes as much.
• The point is about worldview coherence, not any individual’s competence.
• It asks whether naturalism can justify the trust we all already place in reason.

Common misreading: ‘Atheists can’t think’ is not the claim — the target is naturalism, not people.

Why It Matters

Trusting the Tool You Reason With

• Every worldview has to account for the reliability of human reason.
• Naturalists offer accounts; theists offer accounts; the debate is which fits better.
• The argument makes that shared burden explicit and hard to ignore.
• Taking it seriously sharpens both sides, whatever one finally concludes.

A shared task: Grounding trust in reason is a challenge for every worldview, not just naturalism.

The Bottom Line

A Question Worth Sitting With

• The Argument from Reason is provocative, influential, and far from proven.
• It exposes a real tension between blind origins and rational authority.
• Honest naturalists and theists alike can debate it without caricature.
• Its value is the question it forces, not a verdict it settles.

In one line: The argument asks whether naturalism can justify trust in reason — a challenge about worldviews, not a slur on anyone’s intelligence.