This essay seeks to explain Aquinas’s account of natural law, natural inclinations, and absolute moral norms. According to Aquinas, everything bears the impress of divine wisdom (the divine Word); the cosmos is intelligible and has a teleological order. Aquinas describes this order as expressive of God’s “eternal law,” by which creatures are moved to their perfective ends. Human natural inclinations pertain to how God moves us by our rational nature, as we incline rationally toward the goods that perfect our powers. Since the rational soul is the “form” of the body, everything about the body pertains to the flourishing of the rational creature in interpersonal wisdom and love, rather than being merely a biological substratum. We come to know the human good in the process of seeking particular goods perfective of our modes of existence or powers. The above points ground Aquinas’s account of synderesis, the core precepts of the natural law, and absolute moral norms. These norms, whose intelligibility is darkened by the effects of sin, are reflected in the Decalogue, the teaching of Jesus and Paul, and the Catholic Church’s teaching.
