Hume's discussion of the role of reason in the practical sphere is often read to imply two broad, negative claims: first, that passions and actions can (at most) only be regarded as responsive to reasons in so far as they are either in agreement with or contrary to the instrumental implications of other passions or desires. And second, that there is no properly practical form of inference or reasoning. I argue that Hume's general understanding of practical reason does not support either of these claims. Rather, Hume's explicit discussion of these issues—like his discussion of the nature of probable inference—is intended to lay the foundation for a naturalist account of practical thought that we would today regard as embodying a substantive, non-instrumentalist theory of practical rationality. This account will, indeed, make reason the "slave of the passions," but in a very different sense than the one familiar from most contemporary discussions of Hume.