Part — Merkelbach, Summa Theologiae Moralis
Third Part: On Natural Law
St. Thomas, I-II, q. 91, a. 2.
244. Thesis. In the rational creature there is given a natural law, which is implanted with nature and essentially joined to it, and is known by the natural light of reason.
The first part is certain by faith, since the ordinary magisterium of the Church clearly teaches it from Scripture itself (Ps. IV, 6-7 according to the LXX and Vulgate) against atheists, materialists, defenders of moral positivism, and evolutionists; the other is certain against the traditionalists who asserted that natural law, in the present state of fallen man, becomes known to us only by the light of supernatural revelation or tradition.
It is proved: 1) In Scripture the Apostle teaches (Rom. II, 14-15) that the Gentiles who do not have the law (namely, the positive Mosaic law) naturally (that is, under the guidance of the light of natural reason) do the things which are of the law (which are prescribed by the Mosaic law), are a law to themselves (that is, it is in them), have it written in their hearts; that it is a true law, for whose violation or observance they are accused or defended by conscience; that the law was borne by God, because conscience accuses before God, who according to this will judge them.
- The Fathers say that natural law is in all; that it is not written but inhering, innate, inserted; that it is inscribed in hearts; that nature is the teacher of good work, etc. Thus Justin, Dialogue 93; Origen, on Romans, l. II, n. 7, 8, 9; Tertullian, Against Marcion V, 13; Jerome, ep. 121 to Algasia, q. 8; Chrysostom, hom. 12 and 13 to the people of Antioch; Gregory Nazianzen, or. 28, n. 16; Ambrose, ep. 73; Augustine, on Ps. 57, n. 1; on Ps. 118, serm. 25, n. 5; Gregory the Great, on the Gospels, hom. 31, n. 3; Origen, on Numbers, hom. 10, n. 3; Augustine, Confessions II, 4; Sermon on the Mount II, c. 9; Jerome, ep. 121; Ambrose, De fuga saeculi 3, n. 15; ep. 73; Tertullian, De corona 6; Basil, on the Hexaemeron, hom. 9, n. 3 and 4; Cyril of Alexandria, Against Julian, l. 3; etc.
- Intimate sense and conscience testify that some actions are good, others evil; that these stand in the way of attaining the end or perfect good, while those are necessary to the end and obligatory, so that one who obeys the command attains peace of soul, while one who transgresses the same is agitated by the stings of conscience; from these arises the consensus of peoples in the existence of a law independent of human power.
- Reason teaches the same, which St. Thomas shows thus:
Law can be in something in two ways: in one way in the legislator as in the one regulating and measuring, in another way in the subject as in the thing regulated and measured, because insofar as something participates in a rule and measure, thus it is regulated and measured. But all things which are subjected to divine providence are regulated by eternal law. Therefore all things participate in eternal law in some way, insofar as they have an inclination into their own acts and ends. But the rational creature is subject to providence in a more excellent way, insofar as it is made a participant of providence itself, providing for itself and for others. Therefore in it there is a special participation of eternal law insofar as it has an inclination to the due act and end known to it; and this participation is natural law.
It can be defined: the ordination of the rational creature to the ultimate end, founded in its very nature and perceived by the natural light of reason; or the participation of eternal law in rational nature, the ordination impressed upon the created mind by which eternal law is participated in it.