VERITAS VEL MENDACIUM?

A philosophical analysis of lying in Patristics and Scholasticism

Abstract

This investigation examines the doctrine on lying in Saint Augustine and Saint Thomas Aquinas, two pillars of medieval Christian thought, through exegetical analysis of their fundamental texts De Mendacio and Contra Mendacium by Augustine, and Question 110 of the Summa Theologiae (II^a-II^ae) by Thomas. It demonstrates that both philosophers categorically refuse the moral justification of lying, even for apparently virtuous ends, as they conceive truth as a divine attribute and foundation of moral integrity. Augustine rejects the voluntas fallendi (will to deceive) as the formal element of the act of lying, independent of the objective falsity of utterance, condemning all eight types of lies he categorizes. Thomas Aquinas, in turn, asserts that speech possesses the natural purpose of manifesting truth, making lying intrinsically disordered—classifying it as mendacium perniciosum, mendacium officiosum, and mendacium jocosum—but always refusing its permissive morality. The comparison between these doctrines reveals a fundamental continuity in the scholastic tradition in rejecting any legitimacy to deliberate deception. Finally, the contemporary relevance of these philosophical perspectives is analyzed with respect to current questions of digital ethics, combating relativism, misinformation, and the protection of human dignity.