Abstract

Moral motivation refers to the psychological causes that motivate or explain moral action. Moral action refers to action that complies with the requirements of morality. In this essay, I lay out alternative views on moral motivation, giving particular attention the way each view conceives of the explanatory link between practical reasoning and moral conduct. In trying to understand this link, philosophers look to moral judgment. The main rival accounts of the relationship between practical reasoning, moral judgment, and moral motivation can be distinguished according to the way in which they respond to two questions: (1) Can a cognitive (i.e., belief-like) state produce in an agent a motivation at time t, without being accompanied by an affective (i.e., emotional or desire-like) state which exists prior to t? (2) Are moral judgments cognitive states or affective states? I shall defend the Humean theory of motivation, or HTM, as the best account of moral motivation. HTM is often called the belief-desire model of action because it explains behavior by citing a combination of a desire for some end and a belief that a certain action is a means to satisfying that desire. The Humean answer to the first question above is that any process of practical reasoning which generates a motivation is necessarily linked to a non-cognitive state. Regarding the second question, Humeans are split between cognitivists and non-cognitivists. Anti-Humeans, on the other hand, hold that moral judgments express cognitive states, and that cognitive states can independently produce motivations via practical reasoning. I offer two arguments in favor of HTM. First, I suggest that Humeanism meets one criterion of theory choice better than anti-Humeanism. This is the continuity constraint. Given that humans and non-humans evolved common ancestors, the continuity constraint advises us to prefer an account of human psychology which can explain how complex human traits evolved from simpler antecedents resembling the traits of non-human animals. Non-human primates, in particular, are capable of acting altruistically toward con-specifics. Altruistic behavior in primates can shed light on an evolutionary precursor to moral action in humans, since morally significant action often involves altruism. I maintain that a Humean theory of motivation offers the best explanation of altruistic behavior in non-human primates. Therefore, by the continuity constraint, HTM should be the preferred model of the psychological mechanisms underlying human moral motivation, unless empirical evidence strongly suggests otherwise. To ward off the objection that anti-Humeanism is warranted due to the vast differences between humans and non-human primates, I offer a second argument for HTM. This is an argument from a criterion of theory choice called Morgan’s Canon. Morgan’s Canon is a standard of theoretical parsimony according to which a psychological mechanism should be attributed to an organism only if it’s the sole mechanism which can cause some behavior. I argue that HTM meets this criterion much better than anti-Humeanism. This is because the special psychological mechanisms which anti-Humeans postulate to explain moral action are not the sole mechanisms which could produce such action. Rather, the Humean belief-desire model could easily be recruited to explain moral action, as well as a broad variety of non-moral actions.