'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