(Greek: ethos, character)
The natural science of the morality of human acts, which considers the moral actions or conduct of man primarily in the light of human reason rather than in the light of supernatural revealed truth.
Moral theology is sometimes termed Christian Ethics.
The deliberate free actions of man in their relation to right rational nature and the Divine Reason form its subject matter.
The liberty of the human will and the existence of God, the Creator, End, and Rewarder of man, constitute its two most important fundamental postulates.
God is the surety for morality, and without free will man could perform no ethical acts either good or bad; there would be no responsibility, no imputability, no virtues or vices, merit nor guilt, no eternal reward for a life of self-sacrifice and virtue.
Ethics is preeminently a practical and directive science, setting before man not only the absolute obligation of doing good and avoiding evil, but indicating as well how he is to act if he wishes to be morally good and attain the end of his being.
The establishment of the right rules of human conduct and their embodiment in everyday life then forms the primary purpose of ethics, which is generally classified as general or theoretical ethics, dealing with the nature of morality, the end of conduct, its norm, laws, etc., and special or applied ethics, dealing with the relation of such principles and rules to man's personal everyday activities whether individual or social.
Every phase of free human activity, personal, social, economic, political, and international, comes within the scope of ethics, and is regulated by the moral law and made to harmonize with right rational nature or the moral order as Divinely constituted.
New Catholic Dictionary