This section investigates the fundamental definition of justice as a moral virtue and its application within the framework of natural law. Thomas Aquinas, a 13th-century Dominican friar and philosopher, utilizes Aristotelian logic and Christian theology to categorize justice into its various forms, including commutative and distributive justice. The text argues that justice is a constant and perpetual will to render to each person their due, establishing a foundational moral structure for social and legal interactions.

Scholars and philosophers frequently identify this text as a foundational pillar of Western legal and ethical theory. Readers often note the high density of the prose, which requires careful attention to the specific scholastic terminology employed by the author.