Nowadays it is not easy to confess one's own faith without losing one's intellectual honesty. this paper is intended to deal with the spiritual conversion of the intellectuals by briefly reviewing the life of C. S. Lewis. C. S. Lewis tells us how he has come to accept the Christian faith in his autobiographical essay, "Surprised by Joy". The intellectuals are quite reluctant to accept the religious faith, because they face lots of problems. Some of the problems which keep the intellectuals from confessing the religious faith are elaborated in the first half. Among others are the problems of theodicy and existential anxiety included. In the second half, the writer traces the process in which one of the prominent thinkers has come to accept the Christian doctrine of God the Savior. In describing the process of the spiritual conversion, the importance of longing for eternity is emphasized in acknowledging the fact of God. The writer introduces a concept of God as the highest fact of the cosmos, in the sense that God can exist apart from our subjective feeling or desire.