Luigi Caranti's Kant's Political Legacy (2017) demonstrated how Kant has more to say about human rights, peace and development than it appears from most contemporary applications of his work. Complementing this picture, Claudio Corradetti presents us with the legal reasoning behind Kant's writings on international politics. Starting from the emergence of ideas of universal rights and global authority in modern international law, Corradetti gives a masterful account of the origins of Kant's argument in Towards Perpetual Peace (1795). From De Vitoria and Grotius to St. Pierre, Rousseau and Diderot, he presents this story with more nuance than I have previously encountered. At times, one even wonders whether Kant ever produced a radically new idea on these matters or just distilled earlier arguments in his own way. In the second half of his book, Corradetti answers this question by connecting Kant's political reasoning to his original work on topics like freedom, ethics, history and metaphysics. On this basis, he challenges literal readings of Kant's Towards Perpetual Peace as another 'recipe' for how world politics ought to be organised and rather sees it as a 'regulative idea' that should inform any consideration of international law. Corradetti thereby proves Kant's relevance to questions like the division of sovereignty within international organisations and the justification of a universal right to apply for asylum. Not so much a pedagogical endeavour as a rich and somewhat contracted resource, this book turns Kant's 'perpetual peace' into a telescope for observing his broader philosophical universe while making an original contribution to the philosophy of international law and 'global constitutionalism'.