  Some advocates of various forms of internalism have complained that advocacy of external reasons amounts to nothing more than ‘bluff’ (Williams 1979). A natural way to understand this idea is as the complaint that external reasons theorists leave us with too few constraints on what reasons could be, and hence are able to make whatever claims about reasons they want (so long as they endorse them in a serious enough tone of voice, perhaps), with no independent way of checking their plausibility. This complaint could be a fair one against externalists who are willing to offer no general theory about or constraints on reasons, but it is unfair in general. Externalists may simply look for discipline and unity in their views about reasons from a source distinct from facts about motivation or motivational psychology. Value-based theorists, for example, tie their claims about reasons to commitments about what is valuable. So their claims about what we have reasons to do are checked by the plausibility of the corresponding theses about what is valuable.