The Suicide of Reason (EAAN)

The belief that the physical world is all there is. If this is true, then the human mind is not a soul or a spirit, but a physical organ (the brain) shaped entirely by unguided evolution. Here lies the trap.

Natural selection selects for survival (feeding, fleeing, reproducing), not for truth. A false belief that keeps you alive (e.g., believing that a rustling bush is a demon and running away) is genetically superior to a true belief that gets you killed (e.g., staying to investigate).

Therefore, if our cognitive faculties are the product of blind evolutionary forces, we have no reason to trust that they provide us with a true picture of reality especially regarding abstract metaphysical concepts like "atheism." This is known as the Evolutionary Argument Against Naturalism (EAAN).

If Naturalism is true, the probability that our minds are reliable is low. This creates a "defeater" for all our beliefs, including the belief in Naturalism itself. The atheist cuts off the branch they are sitting on, using a brain they believe is a survival machine to make claims about objective truth.

Formal Argument

P1. If naturalism and unguided evolution are true, then human cognitive faculties are shaped by survival and reproductive success, not by a direct aim at producing true beliefs.

P2. Cognitive faculties shaped primarily for survival do not guarantee the production of mostly true beliefs, since many false belief systems can be equally adaptive.

P3. Therefore, if naturalism and unguided evolution are true, we lack a non-circular reason to trust that our cognitive faculties are generally reliable with respect to truth.

P4. If a person lacks justified confidence in the reliability of their cognitive faculties, then that person has a defeater for all beliefs produced by those faculties.

P5. Belief in naturalism and unguided evolution is itself produced by those same cognitive faculties.

C. Therefore, naturalism conjoined with unguided evolution is self-defeating and cannot be rationally affirmed.

Analogy

Imagine relying on a compass that was engineered not to point north, but to guide travelers away from immediate danger like cliffs, predators, or storms. Sometimes it points north, sometimes it points elsewhere, but only insofar as doing so increases the traveler’s chances of survival.

If you later attempt to use that compass to chart the true geography of the land, you immediately face a problem. The compass was never designed to track direction accurately, only to promote survival. Under those conditions, you have no non-circular justification for trusting its readings, including any reading that tells you the compass itself is reliable.

Likewise, if human cognitive faculties are the product of unguided evolutionary processes that select for survival rather than truth, then confidence in those faculties as reliable guides to metaphysical reality is undermined including confidence in the belief that naturalism itself is true.