A critical examination of a non-naturalist’s explanation of moral supervenience

Abstract

In this thesis, I argue that an epistemological characterization of the natural, which classifies the natural as that which demands an a posteriori approach, is the most useful in finding out which properties are natural. Shafer-Landau relies on this characterization to argue that moral properties are non-natural. The non-naturalist is challenged to explain the supervenience of the non-natural moral properties on the natural ones, without thereby considering moral properties as – or reducible to – natural properties. Shafer-Landau succeeds in this mainly because he conceives of moral properties as being realized, and exhaustively constituted, by natural properties. He alludes to the similarity of his position and that of non-reductive physicalism in the philosophy of mind, which argues that mental properties are realized by, but not identical to, physical properties. A discussion of Davidson’s anomalous monism in comparison with non-naturalism will show that this analogy holds, leaving the non-naturalist vulnerable to the non-reductive physicalist’s problems with mental causation. I assess Jaegwon Kim’s argument that mental causation leads to causal overdetermination and conclude that on multiple interpretations of the causal powers of moral properties, it does not hold.