Edward Feser, discussing David Hart on natural law, says, “For Darwinian naturalism, as Hart points out, gives us a view of the mind on which it floats entirely free of truth. Any belief or argument whatsoever could seem absolutely indubitable even if it were completely wrong, if this were conducive to survival.” He takes this as an argument against Darwinian naturalism, which means that he thinks the claim, “Any belief or argument etc.” is either false or implausible.
It is not entirely clear why he thinks this, given that either he agrees, or at least does not disagree, with the biological theory of evolution. However, it may be that, holding that the intellect is immaterial, he believes that it is not subject to the process of natural selection. But this cannot be true. It is evident that whatever the exact relationship between the mind and the body, there is certainly some relationship, and the null hypothesis is basically always false. Consequently, whether or not the intellect is immaterial, there will be bodily causes that influence a person’s tendency to be certain or uncertain about things, with the result that the claim, “Any belief or argument whatsoever could seem absolutely indubitable etc.”, will surely have at least some truth.
It is also clearly true from experience. For example, in Muslim societies, most of the population are extremely convinced that Islam is true, even though this is completely wrong, but very conducive to survival, since even in the present day the death penalty continues to be used against apostates from Islam.
Obviously Islam has not existed long enough for natural selection to have much effect here, however, so in fact this particular case is probably part of a more general situation where agreeing with the people around is “conducive to survival”, both in the literal sense, and in the sense of producing economic and social advantages.
Nor does this imply that the mind “floats entirely free of truth”, since in most cases wrong beliefs about the world are harmful, and true beliefs helpful. If there is a pit of spikes in front of me and I believe that there is not, this is not conducive to survival at all. It does imply that the mind is not perfect and that there is a need to reflect on its work and frequently correct it. The possibility of self-reflection provides possibilities for progress in truth, even given the existence of such mental flaws.