ARE MORAL FUNCTIONALISM’S MORAL A PRIORI COMMITMENTS REALLY A PRIORI?

Abstract

Moral functionalism, a metaethical theory developed by Frank Jackson and Philip Pettit, claims that we can attain moral knowledge by ascertaining the commonplaces about morality that are typically accepted by actual agents. It has important a priori commitments; whilst we may discover a posteriori that a particular descriptive property is identical to a particular moral property, it is a priori that the thing that is identical to the moral property, whatever that thing actually is, plays a particular role. Jackson holds a particular metaphysical position, and moral functionalism is a development of that position as it applies to ethics. In this paper I adapt an objection made by D.H. Mellor against Jackson’s metaphysics to show that moral functionalism’s a priori commitments are actually a posteriori. We can only discover if moral functionalism’s purportedly a priori claims are true through a posteriori investigation.