Does naturalism undermine reason?

There is a serious, self-undermining problem here - not that atheists cannot reason well (plainly they can and do), but that naturalism, taken as a complete account of everything, struggles to justify trusting reason at all. On naturalism the mind is the product of causes that are not themselves rational - blind physics and an evolutionary process that selected our ancestors for survival, not for truth. If every belief is simply the last link in a chain of non-rational causes, then none is held because it is true; each is held because the atoms did what atoms do. And that verdict turns on itself, applying to the belief "naturalism is true" as much as to any other.

The atheist geneticist J. B. S. Haldane felt the bite: if his mental processes were determined wholly by the motions of atoms, he had "no reason for supposing my beliefs are true." C. S. Lewis pressed the difference between a belief's cause and its rational ground, and Alvin Plantinga sharpened it into his Evolutionary Argument Against Naturalism. Selection rewards adaptive behavior, not true belief-content: his caveman "Paul" might flee a tiger because he wrongly thinks it a friendly cat best escaped by running. The behavior survives; the belief is false - so the naturalist inherits a defeater for the reliability of his own faculties, naturalism included.

The strongest reply - true beliefs help you survive - is the one to beat, and the debate continues. But on naturalism a belief drives behavior through its neurophysiology, not its meaning, and countless false contents fit the same useful behavior. This does not by itself prove God; it is one strand suggesting that minds are better explained as deriving from a Mind than from mindless matter.