Book excerpt: Benjamin Kiesewetter defends the normativity of rationality by presenting a new solution to the problems that arise from the common assumption that we ought to be rational. Drawing on an extensive and careful assessment of the problems discussed in the literature, Kiesewetter provides a detailed defence of a reason-response conception of rationality, a novel, evidence-relative account of reasons, and an explanation of structural irrationality in terms of theseaccounts.