That religion has a natural history, being included under the concepts that constitute the sciences of biology, psychology, and sociology, may by this time be assumed without argument. Details of the movement remain to be determined, but there is no longer any occasion to ask whether religion, or some form of it, is interpolated into the system of nature. But to adopt a principle is not the same as to apply it consistently. In spite of good intentions, remnants of the older view become incorporated into our would-be scientific structures. As instances, Professor King, in the book under review, specifies Max Müller's “perception of the infinite,” Morris Jastrow's “religious instinct,” Tiele's “innate sense of infinity,” Brinton's postulate of “ a religiosity of man as a part of his psychical being,” and the theological notion of the gradual revelation of a specific and so-to-say pre-determined idea of God. In all these King sees only so many interpolations. They inject a formed religious consciousness into history, instead of explaining the genesis of the consciousness itself. The author therefore undertakes to show how religion first emerges out of a pre-religious type of life, and how ceremonial, the gods, and the development of high religions can all be fully accounted for by strictly natural conditions. Whether or not all his conclusions are convincing, he has produced a book that must be reckoned with.