Humean Moral Motivation

Abstract

This chapter argues in favour of the Humean theory of motivation as the best account of moral motivation. Humeanism is often called the ‘belief–desire model’ of action because it explains all intentional behaviour – including moral behaviour – by citing a combination of a desire for some end, and a belief that an action is a means to achieve that end. I offer three arguments in favour of Humeanism. First, I suggest that Humeanism meets a criterion of theory choice better than its theoretical competitors: the continuity constraint. Humeanism is consistent with an evolutionary etiology which explains how the moral motivations of modern humans could have evolved from simpler precursors resembling the psychological traits of nonhuman primates. Secondly, to ward off the objection that nonhuman primates are too different from humans to provide any insight into moral motivation, I draw on another criterion of theory choice called Morgan’s Canon – a standard of theoretical parsimony according to which a psychological mechanism should be attributed to an organism only if it is the sole mechanism which can explain some behaviour. I contend that Humeanism meets this criterion more successfully than rival accounts of moral motivation, on the grounds that the Humean belief–desire model can successfully explain both moral and non-moral action. Finally, a third argument appeals to the success of the Humean model of utility-maximization in predicting moral action and its neural correlates.