토마스 아퀴나스의 실천이성과 자연법

This article presents an intellectualistic interpretation on Aquinas’s theory of natural law, which puts greater emphasis on the role of practical reason. The mainstream position after Aquinas views law primarily in terms of will, and the legalistic moral theology based on it seems to make it difficult to see the connection between natural law and practical reason. Natural law is not derived from, but founded upon the first principle of practical reason: Good is to be done and pursued, and evil is to be avoided. Specific legal obligations such as prohibition of murder, upbringing of children, and avoidance of ignorance consist in the orderly direction of human inclinations to the goal of human perfection. According to this interpretation, the role of precepts of natural law is to guide rather than to command. By applying the idea of final causality of practical reason to law, the alleged conflict between the legalistic thinking and Aristotelian practical reason can be resolved. Moral and legal normativity is based on the moral structure of law that the practical reason produces by pursuing the human perfection in the society. In Aquinas, practical reason plays a pivotal role in the understanding of natural law, and in the connection between natural law and morality.