An Institutional Congruence Approach to the Doctrine of the Just Price: The Possibility and Impossibility of Regulative Pricing Rules and Constitutive Market Structures in Christian and Islamic Traditions

This article adopts a theoretical–institutional approach to examine the possibility and impossibility of formulating the doctrine of the “just price” in the Christian and Islamic traditions. The central question of the study is why the concept of the just price becomes an theoretically articulable problem in the Christian tradition, while it does not acquire a comparable status in the Islamic tradition. The article advances the hypothesis that this divergence stems from a fundamental divergence in the relationship between reason and revelation and in the respective roles of constitutive and regulative rules in the architecture of institutional order. The article argues that within the Thomistic tradition, the epistemic and institutional differentiation between the natural and the divine realms makes it possible to distinguish between constitutive rules of the market and regulative rules of economic justice. This distinction, shaped through the interaction of Aristotelian philosophy, Roman law, and Christian theology, stabilizes into a specific yet tension-laden form of institutional congruence that enables the emergence of doctrines such as the just price. By contrast, in the Islamic tradition, the longitudinal unity of reason and revelation and the constitutive role of Sharīʿa entail that economic justice is embedded from the outset within the institutional structure of the market itself, rather than imposed as an external regulative constraint. Consequently, price determination in the Islamic tradition is less likely to be conceptualized as an independent theoretical problem and is instead articulated within the frameworks of transactional jurisprudence (fiqh al-muʿāmalāt), practical wisdom, and institutions such as the ḥisba. The study concludes that doctrine of the just price reflects a specific civilizational possibility grounded in the epistemic and institutional differentiation of the social sphere; a possibility that does not arise in a comparable form within the Islamic tradition due to its distinctive configuration of reason, revelation, and law.