On Humeans, Anti-Humeans, and Motivation: A Reply to Pettit

Abstract

i. In 'The Humean Theory of Motivation' (hereafter 'HTM') I argued for the thesis that R at t is a motivating reason of an agent A to k if and only if there is some 4 such that R at t consists of a desire of A to 0 and a belief that were he to k he would 4.' I called this 'Pi'. I claimed, further, that Pi is definitive of the Humean theory of motivation. The argument I gave for Pi was relatively simple (HTM, pp. 50-8). It is a commonplace that when an agent has a motivating reason to k his reason is partially constituted by a state that embodies his having b-ing a goal. But how does this map on to talk of beliefs and desires? Well, what belief and desire are may uncontroversially be characterized using the metaphor of directions of fit.2 Beliefs are states that aim to fit the world, whereas desires are states that aim to have the world fit them. This metaphor can be rendered non-metaphorical in terms of a functional analysis. Thus, very roughly, the belief that p is a state that tends to go out of existence in the presence of a perception that not-p, whereas the desire that p is a state that tends to endure in the presence of a perception that not-p, disposing the subject to bring it about that p. Now having b-ing as a goal is also a state that aims to have the world fit it. It too must therefore be a disposition to realize b-ing. But in that case we can say that, since the desire to q is a disposition to realize b-ing, and since we have no good reason to think that any other state is such a disposition (in particular, since we have good reason to believe that no belief is a disposition to 0), so only desires (and certainly no belief) can constitute an agent's having b-ing as a goal. Thus Pi. Call this the 'direction of fit' argument. In 'Humeans, Anti-Humeans, and Motivation' (hereafter 'HAM') Philip Pettit makes two claims against me.3 He insists that, first, I do not 'highlight the really central issue between Humeans and anti-Humeans', and that, second, I do not 'provide arguments which would settle that issue in the Humean's favour' (p. 530). I will consider these claims in turn.