Reason can and should guide one in deciding what to believe, at least in large part. But can reason also guide one's actions and the goals that one aims to achieve through them? This question is at the heart of philosophical interest in practical reason. One's thoughts and discourse about practical matters are full of references to reason, and each day brings with it a fresh round of deliberation over such things as the costs and benefits of alternative lines of conduct. Disagreement over how best to understand these phenomena has focused on two distinct questions: First, is reason itself ever a genuine source of considerations for or against conduct, or is our everyday thought and discourse simply a façon de parler? Second, to what extent, if at all, can such considerations make a difference to what one does? Under the first question, which is...