Title: Justicia, mercado y precio en Francisco de Vitoria
Abstract: For Vitoria, fairness in exchanges does not result from mere consent, but conditions that allow us to speak of a fully voluntary act must be verified: absence of fraud and deceit, which cause ignorance, and that the seller or the buyer do not take advantage of the situation of need on the other side of the market. These are the fundamental prerequisites of a lawful purchase and the basis of the just price formed from the common estimate. Profit in trading activity is lawful if this serves the family or political community, if it “adds something” and if the mere profit is not taken as an end in itself. In addition to these reasons, the profit is lawful if it results from buying and selling at just prices. In short, the exchange between equal people, characteristic of the commutative justice, requires the exchange of equivalent things, this being a principle of natural law.