ARTICLE I: ON AN OATH ADJOINED TO A CONTRACT

864. • An oath, as it is taken here, is the calling of God as witness of those things which are promised by contract. The obligation of an oath differs from the obligation of a contract also in this, that the obligation of an oath affects and binds immediately the person of the swearer, whence it does not pass to heirs; but the obligation of a contract confers on the other a strict right, or right of property, affecting the goods of the contracting party, and therefore the whole obligation passes to heirs.

865. Principles. - I. Contracts void by natural right are not strengthened by an oath. The reason is that an oath is an act altogether extrinsic to the contract, and therefore can in no way supply its force. Hence the axiom: An oath follows the nature of the act.

II. Nor are contracts ipso facto void by positive right strengthened by an oath if they are invalidated directly on account of the public good. The reason is that then the oath would be against the common good, and therefore an immoral bond, which God, the author of society, cannot sanction. But those void only in favor of the promisors must indeed be observed from the virtue of religion until the oath is relaxed, yet not from justice.¹

III. An oath is always invalid whenever it cannot be observed without sin of the one swearing. The reason is that an oath cannot be a bond of iniquity, nor can it obligate against good morals. - Thus all Theologians.

866. Questions. - Query 1° Does an oath strengthen contracts, not indeed those void by positive law, but those only rescindible?

Resp. According to the mind of St. Alphonsus,² it must be answered that the oath and contract must be observed from the virtue of religion (not from justice) even in the case in which rescindibility was introduced with regard for the public good. Thus he says a contract must be observed by a minor who swore that he would restore a loan for consumption, although the dissolubility of this contract was introduced with regard for the public good. It is also clear from the Response to the Question immediately following.

867. • Query 2° Are oaths extorted by fear valid for strengthening contracts void by fear?

Resp. The more common Opinion, and by far the more probable to St. Alphonsus,³ affirms, in the case in which the law does not at the same time void the contract on account of the public good. The reason is sought from the 3rd Principle. But he who swore thus can either obtain relaxation of the oath, or, after the performance of the thing concerning which contract was made, seek it back in judgment, or secretly compensate himself for it.¹