Must we act only on what we know?

What relation is there between knowledge and action? According to Hawthorne and Stanley, where your choice is p-dependent, it is appropriate to treat the proposition that p as a reason for acting iff you know that p (RKP). In this paper, I shall argue that it is permissible to treat something as a reason for action even if it isn't known to be true and address Hawthorne and Stanley's arguments for RKP.