This book contains, almost without change in content or style, the Annie Kinkead Warfield Lectures delivered at Princeton Theological Seminary in February, 1974. The theme of the lectures has been well worked over by contemporary theologians from almost every conceivable angle of Christian thought. Yet the subject was chosen because of a) a life-long personal interest in it; b) a deep conviction about its primary significance for Christian understanding and life; c) the disquiet and challenge that lay in the fact that though many in our day have spoken on the subject none seems to say things I find it necessary to say in order to achieve wholeness in Christian thought and life.