In order to gauge the degree to which natural law ethics answers or challenges ethics as perceived by cultural relativism, it is useful to set forth the way in which ethics may be understood in the context of each system. Natural law can be considered a term meant to encompass moral philosophy and its corollary, moral behavior, in human society, which evolves into a certain shape owing to how the human beings involved in it comport themselves toward one another. Ethical behavior in the context of natural law is that which does no deliberate harm to individuals and that which does not disrupt the welfare and stability of society. Cultural relativism can be said to take the shape of human society, or culture, as the starting point, with ethical behavior a result of the subjective responses that individuals make to the culture.
Theories of both natural law and cultural relativism presume the human rational capacity as well as the human tendency toward forming social connections. But each theory interprets how that capacity functions in a different way. From the point of view of natural law, morality can be enacted because the limits of human prerogatives can be sighted and because human rationalist can recognize and adjust to the demands of eternal moral truth, which comes from God. In this regard, Aquinas cites eternal law and "divine reason," which governs the orderly cosmos, which contains another eternal construction in the form of "a dictate of practical reason" (Aquinas 78). Once cosmic order has been acknowledged, it follows that orderly, rational, practical moral truth can be discerned, specifically in stable social relationships and a shared consciousness "whereby each one knows, and is conscious of, what is good and what is evil" (Aquinas 78). From such knowledge proceeds behavior that embraces the good and avoids the evil, and by extension participates in "eternal reason, whereby it has a natural inclination to its proper ac...