Abstract: In this article I consider Bernard Williams's argument against the possibility of external reasons for action and his claim that the only reasons for action are therefore internal. Williams's argument appeals to David Hume's claim that reason is the slave of the passions, and to the idea that reasons are capable of motivating the agent who has them. I consider two responses to Williams's argument, by John McDowell and by Stephen Finlay. McDowell claims that even if Hume is right, there might nevertheless be external reasons. Finlay also claims that external reasons exist but, rejecting the connection between reasons and motivation, claims that they don't matter—that is, aren't motivationally significant for the agent whose reasons they are. Although I reject aspects of McDowell's and Finlay's arguments, I argue that external reasons do exist and in particular that any agent has an external reason to satisfy the preconditions of his or her agency.