A doctoral dissertation for the Katholieke Universiteit Leuven, this study is presented as ‘the author's effort to learn the method of the history of ideas, and … to concretize the relation between history and philosophy when dealing with a medieval text’ (p. 6, author's italics). The bibliography and its organisation reflect this enterprise of self-education. There is much concern about defining categories like philosophy, theology, political theory and medieval, and with methodology. Much space is also devoted to historical context, predominantly the Conciliar Movement and the corresponding papalism. None the less, the author does get to what he regards as a conceptual, as opposed to an historical, comparison of De concordia catholica and De docta ignorantia, together with an epilogue devoted to the continuation of aspects of De concordia catholica in unity with learned ignorance in De pace fidei. The work begins with the fact that, at the end of his life, Nicholas of Cusa did not include his earliest major writing, the conciliarist De concordia catholica, in the codices of his collected works. De Guzman Miroy labours to bring out a continuity in Cusa's development which Nicholas himself apparently wished to forget. The author compares the De concordia catholica with the (moderately) papalist De docta ignorantia in order to show (convincingly in my view) that the move from one ecclesiastical political theory to another was grounded in a metaphysical shift which went with his reading of the Dionysian corpus and other mystical writings. This monograph is that of a scholar beginning to educate himself, as he indicates, and who has worked carefully and usefully through the historical context, the history of the relevant scholarship broadly conceived, and the texts that he compares. In order to advance further a much more complete and deeper understanding of the philosophical and theological sources of the extraordinarily learned and speculative cardinal would be required. Cusa's Proclean, Dionysian, and Eriugenean Platonism would be entered more thoroughly. That would take the lifetime Nicholas himself devoted to them alongside his momentous practical labours for the unity of the Roman Church, her reunion with Orthodoxy, religious concord and peace. The book's greatest contributions to understanding Cusa are its demonstrations both that his practical, theoretical and religious developments go together and that, despite decisive changes, there are the marked continuities. The author's thesis about how concordantia is modified by its union with learned ignorance and how, by way of differentia, it comes to the unity of religion with the difference of rites of the De pace fidei, is not only worth tracing for the sake of understanding the thought of Nicholas. The reconciling formula of the De pace fidei, composed as an irenic response to the fall of Constantinople to Islam, commands the respectful attention of all who hope to find a way from the present reiteration of the desperate union of international war and religious conflict. The work has a quite extensive analytical table of contents, but unfortunately lacks an index.