1. In most cases we can see, with the help of faith, the wisdom of norms proposed in divine revelation, for they can be reduced to human goods and the modes of responsibility. Integral human fulfillment itself requires that we observe these norms. When we do God’s will in such cases, we clearly act for the human good in which he wishes us to flourish.
2. However, only revelation tells us of some norms. For example, we are to participate in the liturgy; to protect, live within, and hand on the structure of the Church; to carry on and extend the redemptive work of Jesus to all places and times. If these norms had not been revealed, we could not have formulated them (see S.t., 1–2, q. 91, aa. 4–5). They make up what is called “divine positive law.”4 Why should we obey them?
3. The question should not be brushed aside by saying one obviously should do whatever God commands. The mere fact that God commands, considered apart from any moral ground, does not generate moral responsibilities (see 4‑D). That we ought to obey divine positive law is itself a specific moral norm. In asking why, we are seeking this norm’s basis in human goods and modes of responsibility.
4. Religion—harmony with God—is a basic human good. Once God reveals himself as personal and extends his invitation to intimate friendship, humankind has a moral reason to cooperate with him. The moral basis for accepting God’s invitation by making the act of faith will be explained later (20‑D). Briefly, however, it may be said here that interpersonal harmony and the development of friendship always depend on compliance with the wishes of others. Moreover, the covenant relationship is proposed by God only after he shows it to be in line with human fulfillment.
5. In making an act of faith, one enters into communion with God by a mutual commitment. At the same time, however, one is aware of one’s radical and unique dependence on God. Thus, while the covenant relationship requires our cooperation, only God is in a position to make certain decisions for the life we share with him. These decisions, which determine the requirements of divine positive law, therefore have authority for us—we ought to obey. The precise point of doing as God directs remains to be seen, but we have reason to believe that there is a point and we will understand it in due time. It is reasonable to comply with God’s directions—with divine positive law—even when we do not discern the intrinsic point of doing what he directs (see S.t., 1, q. 21, aa. 1–2; 2–2, q. 104, a. 4).
6. Divine positive law does not require us to do anything inconsistent with openness to integral human fulfillment: We are not asked to offer human sacrifice, to tell lies, or anything of that sort. Taking into account what we know by faith of the redemptive act of Jesus and our role in it, we can see even now that the precepts of divine positive law are fitting. Obedience does contribute to completing God’s redemptive work in our lives and the world at large.
7. Compared with God’s people in the Old Testament, Christians are asked to do little that is not clearly needed for human fulfillment (see S.t., 1–2. q. 98, aa. 1–2; q. 107, a. 4). Though the old law had many detailed requirements, it was of limited help to friendship with God and thus was burdensome. Not only is the law of Jesus much simpler, but by the power of the Holy Spirit it is effective, for we can fulfill it with the new hearts he gives us (see Rom 7.1–6; Gal 4.21–5.6). God treated the Jews with loving care, but only as trusted servants.5 Christians are treated as friends and members of God’s household (see Rom 8.14–17; Jn 15.14–15). Thus the law of Jesus is not burdensome (see Mt 11.28–30).
4. St. Thomas Aquinas, Summa theologiae, 1–2, q. 108, a. 2, seems to limit the positive precepts of the new law to those pertaining to the sacraments. Perhaps Thomas thought the other matters I mention pertain to the sacraments reductively by pertaining to baptism, confirmation, and orders. Or perhaps he was thinking only of precepts fulfilled by individuals individually, not the precepts of Jesus which govern the life and work of the Church as a whole.
5. S.t., 1–2, q. 107, a. 4; and in general qq. 98–108.