Catholic moral theology is a major category of doctrine in the Roman Catholic church, equivalent to a religious ethics. Moral theology encompasses Roman Catholic social teaching, Catholic medical ethics, sexual ethics, and various doctrines on individual moral virtue and moral theory. It can be distinguished as dealing with "how one is to act," in contrast to dogmatic theology which proposes "what one is to believe." Sources of Catholic moral theology include both the Old Testament and the New Testament, and philosophical ethics such as natural law that are seen as compatible with Catholic doctrine. Moral theology was mostly undifferentiated from theology in general during the patristic era, and is found in the homilies, letters and commentaries on Scripture of the early Church fathers. Du