CCC 1951

Law is a rule of conduct enacted by competent authority for the sake of the common good. the moral law presupposes the rational order, established among creatures for their good and to serve their final end, by the power, wisdom, and goodness of the Creator. All law finds its first and ultimate truth in the eternal law. Law is declared and established by reason as a participation in the providence of the living God, Creator and Redeemer of all. "Such an ordinance of reason is what one calls law."² Leo XIII, Libertas praestantissimum: AAS 20AAS — Acta Apostolicae Sedis (official gazette of the Holy See) (1887/88), 597; cf. St. Thomas Aquinas, STh I-II, 90, 1.

Alone among all animate beings, man can boast of having been counted worthy to receive a law from God: as an animal endowed with reason, capable of understanding and discernment, he is to govern his conduct by using his freedom and reason, in obedience to the One who has entrusted everything to him.³ Cf. Tertullian, Adv. Marc, 2, 4: PL 2, 288-289PL — Patrologia Latina (Migne).