Introduction

For ethical naturalists of a certain stripe, externalism about moral motivation is an attractive option. An influential form of ethical naturalism takes moral properties to be natural properties, while maintaining that moral concepts are not reducible to descriptive or non-moral concepts. Moral properties are, on this view, natural properties, and moral terms that refer to these properties play an essential role in the explanation of natural, empirically observable phenomena. These properties are epistemologically accessible to us in the same way that, for instance, physical or chemical properties are accessible to us. According to this view, moral facts are known a posteriori, and the explanatory role of moral terms plays an essential role in moral epistemology; many advocates of such a view will take moral knowledge to be warranted, inter alia, on the basis of “inferences to the best explanation.”

On the other hand, an internalist about moral motivation thinks that there is a necessary, conceptual connection between judging that “x is morally right” and being motivated to x. A non-analytic ethical naturalist of this kind claims, roughly, that moral properties are natural, objective properties and that we learn about their instantiation in the world due to their causal powers. But how could the judgment (or belief) that a certain natural property of this kind is instantiated by a certain action type (or some instances of this type) or a certain consequence of acting in a certain way be conceptually connected to a completely different item in our psychological economy; namely, a motivation to act? Even if one were not inclined to accept the Humean thesis that beliefs cannot motivate on their own in its full generality, the belief or judgment that a certain natural, explanatory property is instantiated by, or is the expected effect of, certain possible actions seems to be the wrong kind of thing to exhibit this kind of conceptual connection to motivation. Thus ethical naturalists tend to accept externalism and explain virtuous and moral behavior by the existence of a desire to act morally, or a desire to perform only actions that are morally right. So moral motivation is explained in terms of a self-standing desire to be moral, which, when coupled with the belief that certain actions are morally right or morally wrong, will engender motivation in a completely unmysterious, Humeanly acceptable way.