Article III. On Conditions Placed upon a Contract

A condition is a quality added to a contract, which for the most part suspends it until it is fulfilled. It is accustomed to be expressed by the particles if, unless, provided that, etc. The condition which can be placed upon contracts is manifold, namely: 1st, express or tacit; 2nd, of the present or of the future; 3rd, possible or impossible; 4th, necessary or merely contingent; 5th, honorable or dishonorable; 6th, potestative or casual, according as it is in the power of the contracting party or is not; 7th, positive or negative; 8th, contrary to the substance of the contract or not.

Concerning conditions the following things are to be noted:

1st. All conditions must be fulfilled in that sense in which the contracting parties are prudently judged to have wished to oblige themselves.

2nd. A condition concerning an impossible thing renders the contract null from the law of nature itself. The reason is that no one can oblige himself to something impossible.

3rd. A condition concerning the present and the past does not suspend the obligation, but immediately either brings it in or does not induce it; because it either exists or does not; therefore here and now either the contract is valid or null.

4th. A condition must be fulfilled not only equivalently, but in its own form. Some except the condition, if you shall marry, which they say is fulfilled by entrance into Religion; otherwise the condition would be base. Except if the condition were determined to some person, for example, if you shall marry Paul, because then a just and honorable reason can be present. Cf. St. Alphonsus, n. 930.

5th. Potestative conditions, or those which depend on the will of one of the contracting parties, are judged fulfilled not only when that is furnished which was enjoined in the manner of a condition, concerning which there can be no controversy, but even if that is not furnished in reality, when he who obliged himself either 1st, impeded the condition from being fulfilled; or 2nd, was impeded by another from satisfying the condition. Cf. Kenrick, tract. 11, nn. 15 and following.