"Since happiness is the perfect and sufficient good, it excludes every evil and fulfils every desire."

"Human acts are those which proceed from deliberate will."

With unmatched clarity and depth, Summa Theologica (Prima Secundae) presents Thomas Aquinas's most influential treatment of moral philosophy and ethics. Here, Aquinas confronts the fundamental questions of human life: the nature of happiness, the structure of moral action, the formation of virtue and vice, and the role of law and grace in directing human freedom toward its proper end.

This volume examines the inner workings of human action-intellect, will, passions, habits-and builds a comprehensive moral framework rooted in reason and elevated by theology. Drawing upon classical philosophy, especially Aristotle, Aquinas articulates a vision in which moral law is not arbitrary but grounded in human nature itself. His methodical approach, presenting objections and reasoned responses, invites disciplined reflection and intellectual rigor.

Enduring in relevance, this work continues to shape Catholic moral theology, virtue ethics, natural law theory, and Western ethical thought. Its insights speak as powerfully today as they did in the thirteenth century, offering a coherent and profound account of how human beings are ordered toward the highest good through right action, cultivated virtue, and divine assistance.