Is God Giving or Trading? Thomas Aquinas's First Use of “Just Price”

Abstract The phrase “just price” first appears in Aquinas's Commentary on the Book of Isaiah (1252). Interestingly, even in this early work Aquinas introduces the notion of price to comment on a verse, a term which had in fact disappeared with the Vulgate Latin translation, on which Aquinas relied, and which does not appear in the Fathers’ commentaries. Aquinas here provides the founding elements of his later analyses: the role of the price in ensuring the justice of exchange but also the diversity of possible exchange ratios, not necessarily referring to price, in order to account for limit cases within an exchange framework.