There can be little doubt that one of the world’s greatest books upon religion is the work of Guyau, which appeared in 1886, bearing the arresting title, _L’Irreligion de l’Avenir_. Its sub-title describes it as an Etude sociologique, and it is this treatment of the subject from the standpoint of sociology which is such a distinctive feature of the book. The notion of a _social bond_ between man and the powers superior to him, but resembling him, is, claims Guyau, a point of unity in which all religions are at one. The foundation of the religious sentiment lies in sociality, and the religious man is just the man who is disposed to be sociable, not only with all living beings whom he meets, but with those whom he imaginatively creates as gods. Guyau’s thesis, briefly put, is that religion is a manifestation of life (again he insists on “Life,” as in his Ethics, as a central conception), becoming self-conscious and seeking the explanation of things by analogies drawn from human society. Religion is “sociomorphic” rather than merely anthropomorphic; it is, indeed, a universal sociological hypothesis, mythical in form. The religious sentiment expresses a consciousness of dependence, and in addition, adds Guyau, it expresses the need of affection, tenderness and love—that is to say, the “social” side of man’s nature. In the conception of the Great Companion or Loving Father, humanity finds consolation and hope. Children and women readily turn to such an ideal, and primitive peoples, who are just like children, conceive of the deity as severe and all- powerful. To this conception moral attributes were subsequently added, as man’s own moral conscience developed, and it now issues in a doctrine of God as Love. All this development is, together with that of esthetics and ethics, a manifestation of life in its individual and more especially social manifestations. It is the purpose of Guyau’s book not only to present a study of the evolution of religion in this manner, from a sociological point of view, but to indicate a further development of which the beginnings are already manifest—namely, a decomposition of all systems of dogmatic religion. It is primarily the decay of dogma and ecclesiasticism which he intends to indicate by the French term _irréligion_. The English translation of his work bears the title _The Non-religion of the Future_. Had Guyau been writing and living in another country it is undoubtedly true that his work would probably have been entitled _The Religion of the Future_. Owing to the Roman Catholic environment and the conception of religion in his own land, he was, however, obliged to abandon the use of the word religion altogether. In order to avoid misunderstanding, we must examine the sense he gives to this word, and shall see then that his title is not meant to convey the impression of being anti-religious in the widest sense, nor is it irreligious in the English meaning of that word.