There is a great principle enunciated by S. Augustine in regard to the Old Testament which requires to be kept constantly in view. It is that as the Old Testament is manifested in the New, so the New Testament is latent in the Old[20]. In order to recognize this there is no discussion necessary of the method by which our 'Old Testament' received its present shape. The evidence of it lies in the Old Testament considered as a finished product. As such, we cannot study that 'divine library' without being struck both by its unity, so far greater than belongs to any other literature[21], and by the fact that like no other literature it looks forward to an end not yet attained, a divine event in which is to be its justification and its interpretation. The Old Testament demands the New to bring out its true meaning: the New appeals back to the Old to bear witness to the continuity of the divine purpose of which it is the outcome. It is from this point of view that we understand the appeal which, in the New Testament, is so constantly made to the older Scriptures. Whether they are appealed to, as in the Sermon on the Mount, as containing the record of a moral education, divine though imperfect, which the Christ was to complete[22]; or as by St. Paul, as the record of a preparatory and temporary discipline by means of external enactments of God, calculated to awaken the dull conscience of men to the reality and holiness of the divine will, and so to make men conscious of sin against God, and ready to welcome the dispensation of pardon and grace[23]; or, as in the Epistle to the Hebrews, as a system of ritual and ceremonial observances, in which were shadowed forth by the inspiring Spirit[24] the deep truths of the still-needed sacrifice, and the access to God not yet won for man; or finally, as by almost all the New Testament writers, as a prophetic dispensation in which the Messianic hope found gradual expression in fuller and exacter lineaments, and produced an anticipation which Christ only could satisfy[25]:--from any of these points of view, or from all taken together, we are concerned only with the Old Testament as it finally appears, not with the method by which it came into being. It cannot be too strongly emphasized that when we seek reassurance in regard to the inspiration of those books of the Old Testament, to which our Lord and His Church refer us, we find it primarily in the substance of the books as they are given to us, not in any considerations of the manner in which they came into existence[26].