Question IV. On Contracts

248. Preliminary Note. As is evident from what was said above in n. 39, a contract is the principal mode of acquiring dominion and draws its origin from the very nature of human society. For man, as a social animal, cannot acquire happiness without the help of other men. Hence no man can truly say that he is sufficient to himself and needs the aid of no one. But in the state of fallen nature, the precept of charity alone does not suffice for aid always to be granted in necessities; hence another means had to be added, namely contracts, by which the works and things of others yield to our utility under certain conditions. Thus, e.g., a poor man needs food; but since he does not have money, he must enter into a contract of labor in order to acquire money. Having obtained money, he enters into a contract of purchase and sale to procure food. Even the richest man needs a contract of purchase to procure for himself many necessities of life. Therefore the origin of contracts is to be derived from natural law itself, with the division of goods, however, presupposed. For if all goods were altogether common, contracts would now be superfluous, since their principal effect is to transfer dominion of some determinate thing from one man to another. Positive laws have further determined the diverse contracts and their conditions.

The tract on contracts is very long, since there are almost innumerable species of contracts and a very great number of statutes of positive laws which seem to oblige in conscience. But it is neither necessary nor possible for a confessor to know all those statutes enacted for the legitimacy of individual contracts. Therefore, studying brevity, we divide this whole tract into two chapters: 1. on contracts in general; 2. on the principal contracts in particular.