Internalism about practical reasons is the thesis that reasons for action depend upon the goals, aims, desires, and interests of the agent whose reasons they are. Proponents of the view argue that its truth would best a number of important metaphysical facts about practical reasons: it would explain the plausible link between normative and motivating reasons; the intrinsic connection between normative judgments and motivation; the distinctive semantic import of reasons-claims as opposed to other kinds of normative claims; and the distinctive role of reasons in interpersonal practices such as advice giving. And the view is intuitive: we often point to motivational features of agents' psychologies to explain the reasons they have, and it's not uncommon that we justify action on the basis of its connection to one of our interests, cares, or concerns. In this dissertation, I argue that despite these points in its favor, no interesting version of practical reasons internalism is true. Properly understood, the claims about normative reasons are not best explained by the truth of internalism. In addition, I argue that the three most prominent variants of internalism are undermined by counterexamples—cases where there is a reason for some agent to act, but the relevant motivational claim does not obtain. While practical reasons internalism should be rejected, I show that examining this view reveals important criteria of adequacy for any account of practical reasons. In the last chapter of this work, I argues for a metaphysical analysis of practical reasons that I call the "standards-based" account informed by these criteria. This account retains all of the attractive features of internalism while avoiding its pitfalls.