This book is both historical and critical. Historically, it situates Kant’s teaching on perpetual peace within the wider range of his writings, especially his lesser known theological essays. Critically, it employs Kant’s philosophical anthropology as a framework for highlighting the defects of cosmopolitan IR theory as exhibited for instance by Pogge, Beitz, and Held. The book’s main thesis is that Kant’s ‘ideal theory’ (to borrow a phrase from Rawls) of perpetual peace is constructed to overcome the deficiencies of human nature that he believed are best understood through theological analysis. The author accordingly directs much attention toward elucidating Kant’s conception of ‘radical evil’, ‘salvation’, ‘rational faith’, and related topics. In so doing, the author faults the selectiveness of contemporary liberal peace theorists such as Doyle, who seize on some aspects of Kant’s writings while abandoning others as artifacts of Western culture’s obsolete theological past. The author does well to point out that the problem is not simply that Kant’s thought on peace is thereby rendered incoherent; rather, the internationalist political program of these theorists is severed from any solid anchoring in human nature. Their prescriptions for achieving a stable peace, with a nearly exclusive focus on the design of better institutions, remain unachievable in the absence of a philosophical anthropology. Kant, by contrast, provided a coherent account of how human beings in society move from ‘is’ to ‘ought’. The author does not subscribe to the theological particulars of Kant’s diagnosis of the human condition and the pathway for overcoming its limitations. But a solid case is made that the elements provided by Kant provide invaluable guidance for constructing an operationalizable theory of peace.