§ 1. On the Validity of an Oath

603. PRINCIPLE. For a valid oath there are required: the intention of swearing and a swear-formula. These two are essential; nevertheless the first parts are held by intention, so that, although God is invoked as witness only internally, an oath is present.

I. The INTENTION OF SWEARING is required, at least virtual; because without such an intention an oath, as an invocation of God, is not a human act (III, 134).

Hence: 1. If the mind of swearing is lacking, whether from inadvertence, as in him who does not know or does not notice that the words which he uses are sworn words, or who does not intend to usurp them as sworn words but only wishes to affirm more expressly the things which he says; or from malice, as in him who swears fictitiously, by positively excluding the intention of invoking God as witness, there is no oath. 2. The same must more probably be said concerning a promissory oath, if the mind of obliging oneself from oath, or from religion, is lacking; because it is contradictory to will to promise by swearing and to be unwilling to contract an obligation of religion. 3. If only the mind of fulfilling the promise is lacking, the oath is valid, since the intention of truly swearing is present; but perjury is committed, on account of defect of truth, as will be said n. 606. Cf. St. Alph., III, 172.

II. A SWEAR-FORMULA is required, by which it is expressly or tacitly manifested that God is invoked as witness. Otherwise how could God be employed in a sensible way as witness before others? (III, 134).

Moreover: 1. The invocation is EXPRESS whenever God or his attributes are brought into the midst for making faith. Of this sort are the following formulas: I attest God, I call God to witness; let God be witness to me; I swear by God, by Christ, by the truth of God, by the faith of God, by his mercy, justice; may God destroy me, if, etc. (III, 140-143).

2. The invocation of God is TACIT when it is done through nobler creatures, insofar as divine perfections shine forth in them, for example: I swear by the Blessed Virgin, by the Saints, by heaven, etc.; likewise when signs alone are employed, for example hands are raised, the Gospel is touched, if from a preceding determination those signs are held as a swear-formula (III, 135-138). Indeed, this determination being presupposed, the contact of hands alone suffices, which officials of the State, priests, or even those who are enrolled in the sect of Mennonites, use in some regions, so that they assert the truth of the matter before a judge.

604. Hence it is inferred: a) If the divine persons or perfections, or the aforesaid creatures, are simply remembered for the sake of affirming and merely by way of narration or similitude, formulas of this sort are not reputed sworn formulas, unless something else is established or argued from the circumstances. Thus he is not considered to swear who says: "I speak before God, the angels, the blessed; God knows; God knows all things; God sees my conscience; hold me as innocent of this evil as the angels of God; it is as true as God exists; God lives before whom I stand, etc." (III, 134-138).

b) Execratory formulas, as for example, "may I be killed if this is not so," are commonly not considered a true oath, unless God is expressly named, for example: May God destroy me, if I lie. Otherwise they contain only a certain sponsoring or obligation of penalty (III, 143; l. El. qq. ref., n. 19).

c) Of itself, the invocation of one's own conscience, faith, life, body, one's own affairs, or a common creature does not suffice for an oath: for example, "I swear from conscience, by conscience, by my faith, probity, by priestly honor, military honor, by my head, by honor, by house, by children, etc." But otherwise, if one swears by the faith of Christ or the Catholic faith (III, 134-135). Nevertheless a promise made by invoking priestly honor is altogether serious and obliges.

d) Similarly, he does not swear who says: "I swear that it is so; I swear that I am going to do this"; unless from the previous declaration of the one swearing or of the one asking, the intention of furnishing a true oath is manifest (III, 136).

e) A lay oath, as they call it, is not an oath, since invocation of God is lacking (Ami du Cl., 1908, p. 870).

PRACTICAL RULES. 1. In the INTERNAL forum, the matter is to be judged from intention. He who has the mind of swearing truly swears, whatever words or signs he uses. Indeed he truly swears, even if he uses words which do not import an oath, if he believes it to be an oath. In doubt concerning the intention of the one swearing, one is accustomed to judge according to the common acceptance of the words which he used (III, 134; Lehmkuhl, I, 554).

2. In the EXTERNAL forum, one must stand by the formula which the one swearing usurped. For, although perhaps the oath is null before God because of defect of intention, nevertheless, in the external forum he is judged to have sworn who usurped such a word or such a sign which either of itself or because of circumstances attests a true oath.

Note. Concerning the oath in the declaration of revenues, see n. 967.