Muhammad founded a World-State as well as faith; as Islam spread from its first centers, Muslim political thinkers had to apply the divinely revealed law of the Prophet to new circumstances. They had to relate new realities of power and authority to the ideal constitution which he had laid down and which his immediate successors had elaborated. Against this background, Dr. Rosenthal discusses the later Muslim philosophers who were influenced by the political thought of Plato and Aristotle. He shows how Greek thought modified the Islamic and yet was always subordinated to Muslim categories of thought and political needs. Dr. Rosenthal thus surveys the chief traditions of Islamic political thought from the eighth to the end of the fifteenth centuries. He emphasizes the basic unity given by the shared faith of the writers, without diminishing the individuality of each. Orientalists will welcome the book; so will historians of the medieval West, for it shows them the religious, political, and intellectual positions underlying the expansion of Islam.