as its data all sorts of moral beliefs, customs and practices prevalent at any time among men; but it is not a speculative science which would merely aim at _a posteriori_ inferences or inductive generalizations from these data; it is a practical, _normative_ science which aims at discovering the truth as to what is the right and the wrong in human conduct, and at pointing out the right application of the principles arising out of this truth. Hence it is of supreme importance for the philosopher of morals to determine whether the human race has really been vouchsafed a Divine Revelation, and, convincing himself that Christianity contains such a revelation, to recognize the possibility of supplementing and perfecting what his own natural reason can discover by what the Christian religion teaches about the end of man as the supreme determining principle of human conduct. Not that he is to take the revealed truths of Christianity as principles of moral _philosophy_; for these are the principles of the _supernatural __ Christian Theology_ of human morals; but that as a Christian philosopher, _i.e._ a philosopher who recognizes the truth of the Christian Revelation, he should reason out philosophically a science of Ethics which, so far as it goes, will be in harmony with the moral teachings of the Christian Religion, and will admit of being perfected by these. This recognition, as already remarked, will not be a hindrance but a help to him in exploring the wide domains of the individual, domestic, social and religious conduct of man; in determining, on the basis of theism established by natural reason, the right moral conditions and relations of man’s conduct as an individual, as a member of the family, as a member of the state, and as a creature of God. The nature, source and sanction of authority, domestic, social and religious; of the dictate of conscience; of the natural moral law and of all positive law; of the moral virtues and vices—these are all questions which the philosopher of Ethics has to explore by the use of natural reason, and for the investigation of which the Christian philosopher of Ethics is incomparably better equipped than the philosopher who, though possessing the compass of natural reason, ignores the beacon lights of Divinely Revealed Truths.