As important as Aristotle's economic ideas were to the formulations of Albert, Aquinas, and succeeding masters at Paris and Oxford, they constituted only a part of the textual inheritance on economic questions. In Aquinas' most thorough discussion of usury and just price in the Summa theologiae, Aristotelian insights from the Ethics and the Politics shared place with citations from the Bible, patristic authorities, post-patristic theological writings, Roman authors, and, importantly, Roman law and canon law. In varying degrees scholastic perceptions of money and market exchange were influenced by all these textual traditions.

In addition, scholastic economic thought was strongly influenced by its Christian setting – what its continuators took as their responsibility for the care and protection of souls. Economic determinations were tied not only to legal and ethical considerations but to the individual and his salvation. The primary question scholastic thinkers asked concerning economic activity was not “how does it work?,” but “what is permitted and what is not? what is sinful and what is not?” Economic positions were often justified on moral grounds and framed in terms of the moral duty to protect the weak and to enforce economic justice.

Religious, legal, and ethical principles defining economic liceity were in turn tied to conceptions of the “natural order” of things and to Nature itself. Scholastic authors consistently defined usury not only as unethical but as “unnatural.”