It is a tribute to the mentality and versatility of Mngr. Fulton J. Sheen that he can be most widely known as a popular and persuasive radio preacher, and at the same time accepted as one of the foremost Catholic scholars. This important book issues from Mngr. Sheen's scholarly interest, but in the midst of all of his discussion of philosophy, the author maintains his interest in modern man and his problems and endeavors to channel the message of the Church to his needs. Mngr. Sheen is the propagandist and the missionary par excellence but his message is always based on a thoroughly wrought out intellectual basis. Here he is primarily concerned with the impact of modern knowledge upon religion. He deals with the proper use of the reason in religion and restates the proofs for the existence of God given by Thomas Aquinas in terms of modern knowledge. He pays his respects to modern philosophical trends, Marxism, Freudianism, and the materialism often fostered by sociologists and psychologists. This is a book for the scholar, the student of philosophy and religion. While other than Catholic scholars will not agree with Mngr. Sheen, they must all respect the lucidity of thought and intellectual sincerity which lies behind this exposition of a Thomist philosophy in terms of modern thought.