Whether a sale is rendered unlawful through a fault in the thing sold?

❌ Objection 1 : It would seem that a sale is not rendered unjust and unlawful through a fault in the thing sold. For less account should be taken of the other parts of a thing than of what belongs to its substance. Yet the sale of a thing does not seem to be rendered unlawful through a fault in its substance: for instance, if a man sell instead of the real metal, silver or gold produced by some chemical process, which is adapted to all the human uses for which silver and gold are necessary, for instance in the making of vessels and the like. Much less therefore will it be an unlawful sale if the thing be defective in other ways.

❌ Objection 2 : Further, any fault in the thing, affecting the quantity, would seem chiefly to be opposed to justice which consists in equality. Now quantity is known by being measured: and the measures of things that come into human use are not fixed, but in some places are greater, in others less, as the Philosopher states (Ethic. v, 7). Therefore just as it is impossible to avoid defects on the part of the thing sold, it seems that a sale is not rendered unlawful through the thing sold being defective.

❌ Objection 3 : Further, the thing sold is rendered defective by lacking a fitting quality. But in order to know the quality of a thing, much knowledge is required that is lacking in most buyers. Therefore a sale is not rendered unlawful by a fault (in the thing sold).