Evolutionary debunking of moral realism

Abstract

This thesis aims to clarify and strengthen an epistemological challenge to moral realism. I argue that evolutionary influence defeats the epistemic justification of beliefs about objective moral truths. Realism leads to skepticism. The evolutionary debunking argument challenges the two branches of moral realism on two levels. It challenges nonnaturalism by showing how evolutionary influence is evidence that nonnaturalist moral beliefs are insensitive to truth. It challenges naturalism on the basis that the belief about moral-natural identity is similarly defeated by evolutionary influence. A plausible version of conservative epistemology offers a limited, prima facie support to realist moral beliefs. On the basis of this conservatism, realism enjoys a prima facie, defeasible initial advantage. This initial advantage puts the burden of proof on the debunker who denies the justification of realist moral beliefs. The epistemic defeater in the evolutionary debunking argument is best understood as a belief that renders the subject irresponsible in making sure that her beliefs are sensitive to truth. Evolution has had a doxastically-discriminating influence on the vast majority, if not all, of our moral beliefs. The apparent maladaptiveness of some moral beliefs can be evolutionarily explained (away). The belief in the evolutionary account of moral beliefs can serve as such an epistemic defeater, because given the influence evolution has on our moral beliefs, these beliefs would persist no matter the truth. Using a third factor to establish the harmony between moral truths and moral beliefs relies on question-begging assumptions. Some realists mistakenly think that they are entitled to all the assumptions of the debunker. Due to differences between the evolutionary histories of our moral versus factual beliefs, the debunking argument does not spill over to perceptual beliefs.