From Medieval Virtue to Global Governance: St. Thomas Aquinas, Islamic Finance, and the Ethical Boundaries of the "Just Price" and Usury

Abstract

This paper examines the enduring relevance of St. Thomas Aquinas’s economic philosophy—specifically his concepts of the "just price" (justum pretium) and the prohibition of usury—within contemporary regulatory and financial frameworks. While modern economic theory largely relies on subjective value and market clearing mechanisms, Thomistic ethics grounds economic exchange in commutative justice and the common good. This study explores how Aquinas’s dual skepticism toward marketplace exploitation and unearned capital accumulation translates into modern legal instruments. By contrasting the efficiency-driven, consumer-welfare model of the United States with the social-market orientation of the European Union, this paper evaluates how contemporary interventions such as price-gouging legislation, antitrust enforcement, consumer protection laws, and credit regulations reflect, adapt, or depart from medieval scholastic principles. Furthermore, the study incorporates a comparative analysis of Islamic commercial jurisprudence (Fiqh al-Mu'amalat) and modern Islamic Finance—demonstrating how non-Western asset-backed frameworks operationalize parallel anti-usury and risk-sharing mandates in the contemporary global economy.