This book is the fourth in the Beacon series of Studies in Freedom and Power. It is significant that in the attempt to present and interpret the most characteristically American of the freedoms -- that of religion -- Mr. Blau does so as a philosopher, concerned especially with clarifying the conceptual pattern of the idea. Even the phrase ""freedom of religion"" is so variously used and so often misunderstood that the major issues involved have often been deliberately obscured. ""It is time now,"" says Mr. Blay, ""when defenders of traditional American freedom must either speak out or lose religious liberty in the name of religious liberty"". The great statements of American champions of this liberty are each prefaced by a skillful interpretation. The questions raised and the felt necessities of great moral leaders down the years give a tremendous picture of the foundations on which we must build. The book begins with The Bloody Tenent of Persecution of Roger Williams (1644), outlines the struggle to keep the wall of separation between church and state as Jefferson and Madison stated it; includes the great arguments for keeping religion out of politics, out of the public schools, and ends with the opinion of Justice Frankfurter in the Vashti McCollum case of 194. The format of the book is excellent, and the thorough scholarship of the author is evidenced throughout. This should be a valuable source book for those who may find in the historic expression of free Americans suggestions for new words and ways to defend the freedom of religion today.