Natural Law Ethical Theory

This is an ethical theory that holds one or more of the following three claims: (1) moral claims are not social conventions but are based on the objective nature of things; (2) moral right and wrong depend on facts of [Page 1486]human nature; and (3) an immoral rule cannot be a valid law.

All three of these claims are found in the writings of ancient and early medieval Greek and Roman thinkers. The view that moral claims are not conventional but are based on the objective nature of things is stated by Aristotle, who notes in the Nicomachean Ethics (Book V, Chapter 7) that natural justice consists of moral claims that are “unchangeable and equally valid everywhere and do not depend on whether or not we accept them,” while merely legal justice consists of social norms that “have been laid down by rule [and] differ from place to place.” The view that moral right and wrong depend on the facts of human nature was advanced by ancient Greek and Roman Stoics, such as Cicero, who claims in On the Laws that “the nature of justice must be sought for in the nature of man.” And the view that an unjust or immoral rule cannot be a valid law is famously stated by the early medieval bishop St. Augustine who declares in various writings that “an unjust law is not a law.”

The medieval theologian St. Thomas Aquinas drew together all three of these claims into a comprehensive natural law theory that is commonly taken as the paradigm example of a natural law theory. Aquinas characterized what he called the “Eternal Law” as the regularities that are exhibited in the behaviors of the things that make up the universe that God created. These regularities, he claimed, are the products of the natures that God instilled in things when he created them. In particular, the regular lawful behaviors of things in the universe are the outcome of the “inclinations” that are built into the nature of each thing and that move each thing toward its proper ends. The “natural law,” according to Aquinas, is the eternal law as it applies to human beings. Like all other things in the universe, human beings have inclinations toward their own proper ends, and these inclinations are part of their human nature. Unlike other things, however, the inclinations that orient human beings toward their ends are inclinations that are exhibited in their reasoning processes. In particular, human practical reason is inclined to seek what is good and to avoid what is evil. Aquinas identifies four specific goods that reason perceives as part of the human good and, therefore, as goods that human practical reason is inclined to seek and whose destruction practical reason perceives as evil and, therefore, is inclined to avoid. These four goods are human life, the procreation and care of the young, knowledge of God, and social order. The “precepts” of the natural law, then, consist of the moral claims that derive from the recognition of each of these ends as part of the human good: Human life ought to be sought and its destruction avoided; the procreation and care of the young ought to be sought and its destruction avoided; knowledge of God ought to be sought and its destruction avoided; social order ought to be sought and its destruction avoided. Human laws—that is, the rules promulgated by a ruler—can have the binding force of a valid law, he claimed, only to the extent that they are consistent with the moral precepts of the natural law. A rule that contravenes any of these moral precepts lacks one of the defining characteristics of law and so is not a valid law and has no moral claim on our obedience.

...