The establishment of Christianity, in its Greco-Judaic form, as the favored religion of the Roman Empire by the edict of the Emperor Constantine is rightly regarded as one of the most important events not only in the history of the Empire but also in that of the Western world. What made this act, or rather the religious revolution it registered, of such transcendent importance was the fact that the ascendancy of the new religion meant the ascendancy of a new moral ideal; for Christianity, unlike Stoicism, did not merely act upon the old classical ideal of excellence to modify and remold it, but superseded it by another made up largely of a wholly different set of virtues. It was this new ethical element thus introduced into Greco-Roman civilization which was the most dynamic of the forces active in the transformation of the ancient into the medieval world. The new ideal re-created ethically the Roman world and made Europe for a thousand years and more--until the Renaissance of the fifteenth century called forth again the ethical thought and feeling of classical antiquity--in moral conviction and striving an extension of Asia. A prerequisite to an intelligent study of the history of this new moral ideal is a knowledge of the beliefs and theological doctrines out of which it arose; for this ideal has through the centuries followed the fortune of these beliefs and teachings. In the immediately following pages we shall indicate what were some of the most influential of these ideas and doctrines. I. RELIGIOUS IDEAS AND THEOLOGICAL DOGMAS MOLDING THE IDEAL [Sidenote: The doctrine of a moral law supernaturally revealed] Among the doctrines of Christian theology freighted heavily with ethical consequences was that of a moral law supernaturally promulgated. This was essentially an Oriental conception, a heritage of Christianity from the Hebrew past, and a conception quite alien in general to the manner of thinking of the Greeks and Romans, with whom morality, as we have seen, was a civic and secular and human thing, an expression of man’s essential nature, that is, an outcome of the human reason and conscience. This doctrine exercised an immense influence upon the moral evolution in the Western world. First, it displaced naturalism with supernaturalism in ethics. The whole history of morals records no revolution more momentous than this. Second, it made rigid large sections of the moral code and thus tended to impart for an historical epoch a certain immobility to the religious-ethical side of European civilization. [Sidenote: The teaching of the unity of God and of his universal fatherhood]