Norm, Virtue and Information: the Just Price and Individual Behaviour in Thomas Aquinas’ Summa Theologiae

Question 77 of the Summa Theologiae (IIa-IIae) contains the crux of the analysis Thomas Aquinas devotes to the just price 1. The expression itself (justum pretium) however appears only rarely in these passages 2, and a cursory reading might lead one to conclude only too readily that the object of these few pages is to be found elsewhere. In some respects, such a spontaneous reading would be a fair one. Although Question 77 bears the heading “On the fraud committed in purchase and sale”, its object, which is much more complex, only deals indirectly with the just price. Alone, however, this heading does make it possible to assess the extent of the investigation Thomas Aquinas carries out. This does not in any respect mean drawing up a price theory that would contain its own principle of intelligibility. The objective here, is more limited, and reveals the subordinate character of economic thought: by way of a group of normative prescriptions, tending to distinguish that which is just in commercial transactions from that which is not, the issue is one of enlightening a confessor vis-à-vis his penitent, or even the judge in an ecclesiastical tribunal. From this perspective, the Thomistic construction brings together two levels of analysis. The first involves establishing a referential norm the just price (section 1), whereas the second deals with the circumstances, which allow the priest to obtain the correct information that had caused the transaction price to reach this norm or, on the contrary, to depart from it (sections 2 and 3).