When Paul speaks of salvation by faith, he means the situation in which desires have been changed so that what one wants to do will coincide with what one ought to do, a transformation that humanity cannot bring about by itself alone but that can take place only when the Spirit of God in Christ takes possession of hearts and minds. Salvation, the very essence of Christian mysticism, means a union, or oneness, of the individual and God. In other words, God dwells within the life of the individual, whose nature is thereby changed from that which is prone to do evil to that prone to do good. The earthly career of Jesus is significant because it illustrates what can happen to any human being who allows the Spirit of God to take full possession of him, an idea clearly expressed by Paul when he says, "I have been crucified with Christ and I no longer live, but Christ lives in me."
Paul's argument did not convince all members of the Christian community. Many members, especially those of a Jewish background and understanding, still held to the legalistic view. The conflict between the legalistic and the mystical interpretations of religion can be traced through all of the successive periods of Christian history and is still one of the vital issues in contemporary theology.
