Internalism and the origin of rational motivation

What makes a subject's motivation rational is its originating in her practical reasoning. I explain the appeal of this thesis about rational motivation, and explore its relation to recent discussions of internalism about reasons for action. I do so in the service of clarifying an important meta-ethical debate between Humean motivational skeptics and their Kantian opponents. This debate is one over whether, as this skeptic contends and Kantians deny, considerations about our motivational capacities, together with internalism, restrict genuine reasons for action to merely instrumental ones. I argue that properly adjudicating this debate requires identifying one particular way in which the thesis about rational motivation has been developed - Namely, as a part of what I term "the traditional conception" of the motivational efficacy of practical reason. On this conception, rational motivation consists in choosing some course of conduct out of one's cognitive appreciation of the way its relation to one's practicable good gives one reason to do so. And I side with Kantians against the Humean motivational skeptic in part on grounds that Kant himself - Though not all Kantians - Would find congenial: namely, that we should accept the traditional conception.