Abstract: In this paper I present an argument for the claim that you ought to do something only if you may believe that you ought to do it. More exactly, I defend the following principle about normative reasons: An agent A has decisive reason to Φ only if she has sufficient reason to believe that she has decisive reason to Φ. I argue that this claim follows from the plausible assumption that it must always be possible for an agent to respond correctly to her reasons. In conclusion, I discuss some implications of this argument (given that some other standard assumptions about reasons hold). One such implication is that we are always in a position to be justified in believing all truths about what we have decisive reason (or ought) to do.