In Depth:A Kantian Account of Reason, Melissa Zinkin provides a new and highly original interpretation of Kant's view of reason. Unlike recent interpretations, which claim that for Kant reason is valuable because it is the source of moral value, this book argues that Kant considers reason to be the source of a more fundamental and wider ranging value: depth. Although philosophers often use the term “depth” to indicate a kind of value, they rarely make explicit what they mean. For instance, they strive to make objections that go “deep into the theory” at issue. They stress the importance of beliefs that are “deeply held” and of “deep desires.” They praise works of great “emotional depth.” Often, these references to depth do real work in an argument. Yet the concept of depth itself remains obscure. Zinkin argues that depth is the value of the cognition that results from systematic reflection, which is the distinctive activity of human reason. This value, however, is not just a moral or an epistemic value. Rather, it is best understood as an aesthetic value. In other words, what is good about deep cognition is the same as what is good about our experience of a work or art--it engages us, it makes us think, and it is meaningful. An account of Kant's view of reason as the source of depth has advantages over other accounts because it can solve several interpretative puzzles and can show that, throughout his texts, Kant has a unified view of reason. Moreover, it can reveal the deep connection that Kant saw between our reason and our humanity. An implication of this account is that the deep, rational, reflection that is exemplified, and cultivated, by the arts, is important for other human endeavors, such as science and moral action.