Many pagan, Jewish, Christian and Muslim philosophers from Antiquity to the Enlightenment made no meaningful distinction between philosophy and religion. Instead they advocated a philosophical religion, arguing that God is Reason and that the historical forms of a religious tradition serve as philosophy's handmaid to promote the life of reason among non-philosophers. Carlos Fraenkel provides the first account of this concept and traces its history back to Plato. He shows how Jews and Christians appropriated it in Antiquity, follows it through the Middle Ages in both Islamic and Jewish forms and argues that it underlies Spinoza's interpretation of Christianity. The main challenge to a philosophical religion comes from the modern view that all human beings are equally able to order their lives rationally and hence need no guidance from religion. Fraenkel's wide-ranging book will appeal to anyone interested in how philosophy has interacted with Jewish, Christian, and Muslim religious traditions.

‘In this brilliant and original book, Carlos Fraenkel introduces us to a new strand in the history of both religious and philosophical thought: the idea of a philosophical religion, where reason and religion coincide. Fraenkel leads the reader through the history of philosophical religion, from Plato, through late ancient Judaism and Christianity, through Islam to Spinoza and beyond, transforming our conception of both religion and philosophy.’

Daniel Garber - Princeton University

‘This book is a must-read (and re-read) for anyone interested in the contemporary politics of toleration or the uneasy history of the relations between Faith and Reason. With a remarkable breadth of learning and a keen eye, [Professor] Fraenkel charts the efforts by thinkers from Plato through Hegel to integrate sacred texts and practices into larger philosophical and political world-views. This is both first­rate History of Philosophy and for enthusiasts and sceptics alike an eye-opener about the pre-conditions of secular democracy.’

Calvin Normore - University of California, Los Angeles

‘Fraenkel's brilliant book succeeds in changing the traditional paradigm for which Spinoza brings to a close the long tradition of philosophical reflection on religion, from Philo to the great late ancient and medieval Christian, Muslim, and Jewish theologians and philosophers. For Spinoza, Fraenkel argues, as for his predecessors, the God of Abraham, Isaac, and Jacob is also that of the philosophers, in radical opposition to the claim of his contemporary Pascal. Fraenkel’s new view of the history of a central conception of religion in Western intellectual history is nothing less than a tour de force that should have a significant impact on scholarship.’

Guy Stroumsa - University of Oxford and The Hebrew University of Jerusalem

'… I very much enjoyed reading this book and Carlos Fraenkel is to be congratulated for having produced a provocative and always intelligent argument. Like many good books it raises more questions than it settles, and is a constantly rewarding read.'

Oliver Leaman Source: H-Judaic

'… a bold and exciting new book. … this study is to be commended for both the breadth and depth of its learning and should inspire a rich scholarly dialogue going forward …'

James Bryson Source: Journal of Religious Studies

'… Fraenkel’s monograph is very stimulating and thought-provoking. … The arguments kept ruminating in my mind for some time, which I think is a hallmark of an intellectually intriguing work.'

Anders Klostergaard Petersen Source: Bryn Mawr Classical Review

'A remarkable and important book … It is one of the great merits of Fraenkel's extraordinary book that he helps us to see beyond the Straussian caricature of medieval philosophy … [The book] ranges not only across a broad span of history from the Greeks to the eighteenth century, but also across religious traditions that today's more passionate apologists would prefer to hold apart … [T]he most surprising argument of the book … [is] his revolutionary conclusion that the tradition of philosophical religion has survived into modernity …'

Peter E. Gordon Source: The New Republic

‘No reasonable person can fail to be impressed by the breadth of learning Fraenkel displays in this study and the care and subtlety with which he approaches his sources … I am not aware of any other book that takes on so ambitious a project and executes it so well … [T]he book constitutes a major contribution to historical scholarship.'

Kenneth Seeskin Source: Journal of the History of Philosophy

'Fraenkel’s philosophical credentials, linguistic skills, and command of the pertinent sources are impeccably displayed in this book. No research into the phenomenon of philosophical religion can be conducted without resort to it as a seminal study, and no course can be taught that relates to it without including it in its syllabus. Rather than categorically convincing and putting an end to further discussion, Fraenkel’s book achieves something far better. It will compel scholars to reconsider texts over which they have long considered to be in command, and stimulate reasoned and lively debate concerning vital issues that are not simply academic in nature. Fraenkel’s book authentically provokes in every good sense of the word, and is itself worthy of Spinoza’s parting words in the Ethics - 'all things excellent are as difficult as they are rare'.'

James Diamond Source: Iyyun: The Jerusalem Philosophical Quarterly