This book attempts, from the angle of American secularized religion, to think over William James’s radical empiricism. It reveals that the radical empiricism makes a significant reformation in history of philosophy, which not only breaks with the mind-body dualism in western philosophy, pointing to a new direction, but also originally develops a nature, significance, and purpose of religion, setting up a new religious philosophy. American secularized religion is founded on the radical empiricism. The book assumes that William James’s temperament of philosophy is religious; that religious concern pervades his academic career; that there are religious motives in his system of psychology and philosophy. The main question William James confronts is how religion is possible in scientific times.The essence of the radical empiricism is to make person come back to primordial experience of life, which in itself is just man’s living. Person’s will to believe and religious demand are involved in living. Religious experience of person is the