Darwin’s doubt:
“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 any one trust in the convictions of a monkey’s mind, if there are any convictions in such a mind?” [letter to William Graham, July 3rd, 1881]
If we humans are products of mutations and natural selection only then our cognitive faculties are aimed at survival and not necessarily truth. Therefore we can’t trust our cognitive faculties. After all, our brain sometimes uses illusions to cope with situations that threatens our mental and physical health. We might feel and think we have understood something to be true (like the idea on evolution), but it might just be our brains who keeps us in an illusion favorable for our survival. So Darwinism defeats itself: if it true, then we can’t know if it is true. Like C.S. Lewis said:
“If naturalism were true then all thoughts whatever would be wholly the result of irrational causes. Therefore all thoughts would be equally worthless. Therefore, naturalism is worthless. If it is true, then we can know no truths. It cuts its own throat.”
An Aspiring Krishna Dasa 