The normativity of so-called “coherence” or “structural” requirements of rationality has been hotly debated in recent years. However, relatively little has been said about the nature of structural rationality, or what makes a set of attitudes structurally irrational, if structural rationality is not ultimately a matter of responding correctly to reasons. This paper develops a novel account of incoherence (or structural irrationality), critically examining Alex Worsnip’s recent account. It first argues that Worsnip’s account both over-generates and under-generates incoherent patterns of (...) attitudes, and then proposes an alternative that both avoids these problems and captures a crucial insight behind Worsnip’s account. According to this account, a set of attitudes is incoherent just in case having all of the attitudes in that set is incompatible with reacting to a question in a way that one is, in virtue of having the attitudes, committed to. (shrink)