Abstract

First-order evidence is evidence which bears on whether a proposition is true. Higher-order evidence is evidence which bears on whether a person is able to assess her evidence for or against a proposition. A widespread view is that higher-order evidence makes a difference to whether it is rational for a person to believe a proposition. In this paper, I consider in what way higher-order evidence might do this. More specifically, I consider whether and how higher-order evidence plays a role in determining what it is rational to believe distinct from that which first-order evidence plays. To do this, I turn to the theory of reasons, and try to situate higher-order evidence within it. The only place I find for it there, distinct from that which first-order evidence already occupies, is as a practical reason, that is, as a reason for desire or action. One might take this to show either that the theory of reasons is inadequate as it stands or that higher-order evidence makes no distinctive difference to what it is rational to believe. I tentatively endorse the second option.