Section 3: Conditions of Validity and Licitness

St. Jerome, basing on a passage in the prophecies of Jeremias, lays down three conditions which make an oath lawful. These conditions are often called “the companions of an oath.” They are: (1) truth, (2) judgment, (3) justice.¹ “And thou shalt swear,” the prophet says, “As the Lord liveth, in truth, and in judgment, and in justice.”²

¹ In Ierem. Proph., l. I, c. 4: “At the same time it must be observed that an oath should have these companions: truth, judgment, and justice; if these are lacking, it will by no means be an oath but perjury.” (Migne, P. L., XXIV, 706).

² Jer. IV, 2: “And you shall swear: The Lord lives, in truth and in judgment and in justice.”

1. Truth in an oath is the agreement of the assertion made with the mind and conviction of him who swears; or, in other words, an honest intention to state what is so (when the oath is assertory) or to keep the promise made (when the oath is promissory). Conformity of the statement or promise made with the intention of him who makes it is the essential thing, not the actual correctness of the statement itself.³

³ Gury, Comp. Theol. Mor., I, n. 298: “Truth, that is, conformity of the assertion with the intention and knowledge of the one swearing. It therefore excludes every lie, but not every error. In an assertory oath truth regards the existence of the fact; in a promissory oath, the existence of the intention.”

Truth requires also that he who swears should use words in the sense in which they are understood by others, or in which others have a right to understand them.⁴ This rule excludes intentional equivocation and secret reservation or mental restriction, as these subterfuges would contravene the purpose of an oath, which is to offer a guaranty of truth to others.⁵

⁴ “The oath must be understood according to the mind of the judge who imposes it.”

⁵ Ps. XIV, 1–4; XXIII, 3–6; Heb. VI, 16.—Proposition condemned under Innocent XI, n. 25: “With a cause it is lawful to swear without the intention of swearing, whether the matter is light or grave.”—Ibid., n. 26: “If anyone, either alone or before others, whether questioned or of his own accord, whether for recreation or for any other end, swears that he did not do something which in fact he did, understanding within himself some other thing which he did not do, or another way than that in which he did it, or any other true addition, he does not in fact lie nor is he perjured.”—Ibid., n. 27: “A just cause for using these amphibologies exists whenever it is necessary or useful for the health of the body, the protection of honor or family goods, or for any other act of virtue, so that concealment of the truth is then deemed expedient and deliberate.”—Ibid., n. 28: “One who through a recommendation or gift has been promoted to a magistracy or public office can with a mental restriction take the oath which by the king’s command is customarily required of such persons, without regard to the intention of the one requiring it, because he is not bound to confess a hidden crime.” (Denzinger-Bannwart, n. 1175 sqq.). All these propositions were condemned. Cfr. further on this subject, H. Busembaum, S.J., Medulla, l. III, tr. 3, c. 2, dub. 4: “To swear with equivocation, when there is a just cause and the equivocation itself is lawful, is not evil, because where there is a right to conceal the truth and it is concealed without a lie, no irreverence is done to the oath.”—St. Alphonsus, Theol. Mor., l. III, n. 151 sq., 170.—Gury, Comp. Theol. Mor., I, n. 299: “Question: Is it lawful to swear with a mental restriction? Answer: No, if it is purely mental; but yes, if it is broadly mental and there is a grave cause.”—A. Lehmkuhl, S.J., Theol. Mor., Vol. I, 11th ed., n. 918, 4: “When I lawfully employ a restriction that is not purely mental, it is generally also lawful, in proportion to the gravity of the cause, to swear with such a restriction. But if the questioner has a right to the full truth, to swear with a restriction is altogether perjury; if the other has no right, but the speaker swears with a restriction for a slighter cause, it must be judged from the circumstances of the harms whether it ought to be regarded as perjury or whether he should be said merely to have sworn rashly.”—According to Lehmkuhl the theses quoted at the beginning of this note were condemned by the Holy See for two reasons: first, because not everything contained therein constitutes a legitimate cause, and, secondly, because not everything is understood of mental reservation in the broad sense of the term (de restrictione late mentali). St. Alphonsus and other moralists take also prop. 28 to refer to the restrictio pure mentalis, and others say that it applies to the restrictio non pure mentalis, because there is question here of one of those cases in which mental reservation is absolutely excluded. Cfr. F. A. Göpfert, Moraltheologie, Vol. II, 6th ed., p. 332; IDEM, Der Eid, pp. 211 sqq.; F. Kössing, Über die Wahrheitsliebe, Paderborn 1893, pp. 145 sq.; Jos. Mausbach, Catholic Moral Teaching and Its Antagonists, pp. 113 sqq., New York 1914; Jos. Rickaby, S.J., Political and Moral Essays, pp. 215 sqq., London 1902.

An attempt has been made to apply the doctrine of mental restriction to oaths by distinguishing between the animus iurandi and the animus se obligandi. “The many points of view,” says Dr. Mausbach, “which oaths, and especially promises confirmed by oath, permitted, appealed to the Scholastic desire of making distinctions and admitted of much logical analysis. It was sought to distinguish the interests of truth, religion, loyalty, and justice, which are all interwoven in such an oath, and the question was asked, how far they belonged to the essence of the oath or were separable from it. The larger works on casuistry contain investigations into the relation of the intentio iurandi, the intentio se obligandi (ex religione, ex iustitia, etc.), and the intentio implendi, which are marvels of ingenuity and almost bewilder an ordinary reader, yet are specially designed to avert all misunderstanding. The short summaries of them, however, given in compendia of casuistry, are more open to criticism.

One of the most dangerous of these statements is said to be the assertion that an oath is not valid if the man taking it has an inward intention not to take an oath before God. In this way, we are told, the trustworthiness of the oath is undermined and public confidence deeply shattered.”⁶

⁶ Jos. Mausbach, Catholic Moral Teaching, pp. 108 sq.

Dr. Mausbach proceeds to show at some length that this objection is not justified by the actual teaching of Catholic moralists, who all agree that such a fictio or simulatio is sinful, because it involves a misuse of the name of God, and a lie, since the spoken words contradict the inward thought. We are never allowed to commit even a venial sin. If it is said that the horror of venial sin is not nearly so deterrent in its effect as the dread of committing perjury, and the moralists, by questioning the validity of an oath when it has apparently been taken in all seriousness, favor a distortion of the truth and imperil public confidence, the answer is that the same moralists regard simulation as a very grievous sin when the declaration apparently made under oath is false, no matter whether it concerns an important or a trivial matter, and they do the same whenever the declaration, even if true, is received in a court of law or in any legal proceeding as made upon oath.

The case is similar when, in a promissory oath, the intention of fulfilling the promise is defective. Here the question of the venial nature of the sin committed refers only to the simulation as such. It affects a statement that is true and a promise that is seriously meant, and it does so under circumstances in which neither the State nor the individual has any right to require an oath. “As soon as there is any violation of the truth, the invocation of the name of God, made apparently in earnest, becomes, in spite of the reservation, a grievous insult to God’s honor, about equivalent to perjury. Moreover, just as soon as public or private rights require a declaration to be made under oath, even a true declaration failing to be under oath is to be regarded as a grievous sin. This guards against all abuse of the principle. According to this exposition, a man with an honest intention had better take an oath seriously, for thus he is free from sin; whereas simulatio is in any case a venial sin, and in cases where an oath can legally be required, it is a mortal sin. A man who intends to lie, need not hope to escape grievous sin by means of simulatio; whether he is guilty of perjury in the strict sense of the word is, after all, only a matter of words.”⁷

⁷ Ibid., p. 110 sq. Dr. Mausbach adds in a note (l. c.): “Lugo describes the sin simply as periurium. He says: ‘Nor would he be excused from perjury who, without the intention of swearing, outwardly swore to something false by words which here and now determinately and altogether signify the intention of swearing and of invoking God as witness.’ (De Iust. et Iure, disp. 23, n. 12). The non-fulfilment of a promise made sub ficto iuramento must also be considered equivalent to perjury. For if contempt of God is shown by apparently calling upon Him to witness a lie, it is certainly a great insult to Him to be false to a pledge placed under His authority. There are some moralists who have not made this latter point sufficiently clear.”

To the question, why the moralists did not simply admit that an oath was really an oath, unless some external circumstances plainly showed it to be fictitious or taken in jest, the same writer replies that they did not do so because, according to their ideas of religion and justice, it would have injured the true character and value of an oath. “They recognized the fact that an oath devoid of inward intention must still be treated as a real oath, but that an oath unaccompanied by a serious act of the will should be called a true oath seemed to them as inadmissible as to call a corpse a human being; the soul is wanting in both cases. It was not a lax, but rather a profound, appreciation of the dignity of an oath that caused this view to be adopted. An oath was regarded as an act of the religious life or cultus. Now it was well known that the performance of sacramental rites, though externally perfect, was null and void without the inward intention. Absence of consent in the Sacrament of Matrimony nullifies the mutual pledge and destroys the validity of a marriage, even though the external forum may maintain its validity until evidence to the contrary is supplied. If, in a case like this, where one human being directly confronts another, it is the interior intention that decides the question of validity, this appeared to be still more true in the case of an oath, where a human being stands up before God and invokes Him as a witness and a surety. The specific character of an oath and its quasi-sacramental dignity could not, it was thought, exist if the will did not consent to this specific moral obligation.”⁸

⁸ Ibid., pp. 110 sqq. Cfr. F. X. Linsenmann, Lehrbuch der Moraltheologie, pp. 450 sq.

By the omission of several essential remarks from statements made by St. Alphonsus, Gury, and other moralists, their teaching on the subject of oaths and contracts has been seriously distorted. When they deny the “validity” of a fictitious promise, they do so on the strength of the principle so forcibly pointed out by Dr. Mausbach, and, as a rule, with all the reservations demanded both by a sense of justice and by regard for public security.⁹

⁹ J. Mausbach, ibid., p. 112.

St. Alphonsus, who has been criticized with particular severity for his teaching, on account of a brief reference to the question, says in another place, to which he expressly refers the reader: “In order that human intercourse may remain duly regulated, the natural law requires for the public welfare that there should be no deception with regard to contracts, and therefore it binds those who have recourse to simulatio, in punishment for their deception, to indemnify the deceived party exactly as if no deception had taken place.”¹⁰

¹⁰ Theol. Mor., l. III, n. 709; cfr. Mausbach, op. cit., pp. 112 sq.

2. A man swears with judgment (iudicium in iurante, iudicium discretionis ex parte iurantis) when he has a just cause for invoking the testimony of God, and performs the act with due attention and reverence.¹¹ Judgment presupposes maturity of mind, understanding, and careful consideration of the statement or promise made, together with the full use of reason and will-power and calmness at the time the oath is taken. For this reason minors, weak-minded persons, and those who are insane or under the influence of liquor or drugs, are unable to take an oath. Physical compulsion, essential error, and violent fear which excludes deliberation, make an oath invalid, whereas purely moral compulsion or ordinary fear do not entail invalidity, but merely constitute a ground for dispensation.

¹¹ Gury, Comp. Theol. Mor., I, n. 298: “Judgment, that is, discretion or a reasonable cause for swearing; for an oath, since it is a most holy thing, ought not to be employed indiscriminately, but with piety and great reverence.”—St. Thomas, Summa Theol., 2a 2ae, qu. 89, art. 3, ad 1: “Judgment is not taken here for the execution of justice, but for a judgment of discretion. Nor is truth taken here as it is a part of justice, but as it is a certain condition of speech.”—IDEM, Comment. in Sent., III, dist. 39, art. 2, qu. 3, ad 1–2.

Since an oath can be taken only with due care and deliberation, a man who wishes to swear, or is compelled to do so, is strictly obliged to consider the matter and the circumstances of the case, and must not allow himself to be moved by love, hatred or any other emotion, but solely by the importance and necessity of the oath he is taking, for without careful consideration an oath will nearly always be hasty or indiscreet.¹²

¹² St. Thomas, Summa Theol., 2a 2ae, qu. 89, art. 3, ad 2: “Devotion and faith and all things of this kind which are required for the due manner of swearing are understood in judgment.”—Ibid., art. 7: “If the thing is such that it was not in his power, the judgment of discretion is lacking to the oath, unless perhaps that which was possible when he swore is rendered impossible for him by some event.”—IDEM, Comment. in Sent., III, dist. 39, art. 2, qu. 3, ad 4: “In judgment, which is the discretion of the one swearing, are included the due form, event, and time, and all the things which occur for consideration on the part of the one swearing.”—Cfr. Cat. Rom., P. III, c. 3, qu. 13.—F. A. Göpfert, Der Eid, pp. 219 sqq.

“A just cause [iusta causa iurandi] will be any matter of some importance for the welfare of either soul or body, whether it be public or private. We are not, therefore, justified in swearing to every assertion which we believe to be true; there must be some special reason for employing the name and authority of God to confirm what we say. However, provided that the other conditions are not wanting, the defect of judgment in swearing will not be more than a venial sin, for it is no more than the idle use of the name of God.”¹³

¹³ Slater, A Manual of Moral Theology, I, 242.—Cfr. Gury, Comp. Theol. Mor., I, n. 299: “Question: What is a sufficient cause for swearing? Answer: Any honorable cause of some weight, for example, peace to be confirmed in families, greater security in contracts, etc.”—St. Thomas, Comment. in Hebr., c. VI, lect. 3: “The causes in which it is lawful to swear are these: to confirm peace, as Laban swore (Gen. XXXI, 48); secondly, to preserve one’s reputation; thirdly, to keep fidelity, as feudatories swear to their lords; fourthly, to fulfil obedience, if something honorable is commanded by a superior; fifthly, to provide security; sixthly, to attest the truth.”

3. By justice in swearing (iustitia in obiecto) is meant the moral permissibility or becomingness (honestas) of the matter concerning which an oath is taken.¹⁴ Justice requires that the matter of an oath should be in conformity with the moral law and Christian duty. Thus in an assertory oath the assertion should not be sinful, and in a promissory oath that which is promised must be morally good and lawful.¹⁵ Therefore an obligation assumed by oath to commit an act of injustice or a sin is always null and void.¹⁶ An oath so taken would, of course, be doubly sinful. To this class of invalid and unlawful oaths belong those taken by conspirators in crime, members of forbidden societies, such as anarchists, Freemasons, etc.

¹⁴ Gury, Comp. Theol. Mor., I, n. 298: “Justice, that is, that the oath concern a lawful and honorable thing; thus he would swear against justice who by an oath bound himself to something harmful to his neighbor or forbidden from another source, or who detracted from his neighbor.”—St. Thomas, Summa Theol., 2a 2ae, qu. 89, art. 3, ad 2: “The other two [justice and truth] pertain to the thing about which the oath is made, although it could be said that justice pertains to the cause for which the oath is made.”

¹⁵ Slater, A Manual of Moral Theology, I, 242.

¹⁶ Cfr. Matt. XIV, 7; Mark VI, 22 sqq.; Acts XXIII, 12.—Reg. Iuris in Sexto Decr. Bonifat. VIII, n. 58: “An oath made against good morals is not binding.”—St. Ambrose, De Offic., l. III, c. 12, n. 76: “Let [a Christian] promise nothing dishonorable; and if he has promised it, it is more tolerable not to do what was promised than to do what is shameful.”—Ibid., n. 77: “Herod shamefully promised the dancer a reward and cruelly paid it. It is shameful that a kingdom is promised for dancing; it is cruel that the death of a prophet is bestowed for the sanctity of an oath. How much more tolerable in such a case would perjury have been than fulfilment of the oath? If, nevertheless, it could be called perjury that he swore when drunk amid wine and promised when emasculated amid the dancers’ choruses. The prophet’s head is brought in on a platter, and this was judged to be a matter of fidelity which was a matter of madness.” (Migne, P. L., XVI, 167).

4. Of the formulas employed in swearing some certainly involve an oath, either explicitly or implicitly, whereas others are doubtful, while still others signify no oath at all. a) Explicit forms of swearing are the following: “God be my witness,” “I swear by God or Christ,” “May God punish me if I do not tell the truth,” etc. Even the simple phrase: “I swear,” suffices to constitute an oath if the intention of calling upon God as witness is manifest. b) Implicit forms of swearing are the following: “I swear by the Blessed Virgin,” “by the cross,” or “by the Sacraments,” etc. He who swears thus may justly be supposed to invoke God as a witness to the truth of what he affirms. Ordinarily, however, those who habitually use such expressions as “by God,” “by heavens,” etc., do not think of God, and therefore these phrases as a rule do not imply an oath because the intention is lacking. c) Ambiguous formulas are: “Upon my word,” “Upon my oath,” “Upon my faith,” “As God lives,” “God knows that...,” etc. These phrases indicate a real oath when there is an evident intention to swear, or when they are uttered in court in lieu of an oath. But if there is no intention of taking an oath, such words may be taken simply enuntiative, i. e., as a means of creating confidence, not invocative, i. e., as calling God to witness. Hence, in ordinary conversation, the phrase “I swear that I will do this or that,” or “Upon my oath I will do so and so,” does not, as a rule, indicate the intention of taking a real oath, but merely that of making a solemn affirmation. d) Such expressions as “truly,” “surely,” “certainly,”

¹⁷ H. Noldin, S.J., Summa Theol. Mor., Vol. II, 11th ed., pp. 258 sq.

“As surely as I live,” “I will die on the spot,” “Let my ears be cut off,” “May the devil get me if this is not true,” etc., are mere exaggerations and imply no invocation of God. Therefore if an untruth is affirmed by means of these and similar phrases, this manner of affirmation in itself constitutes merely a venial sin, though the lie may be mortal. Only when the formula contains mention of a punishment to be inflicted by God, as, “May lightning strike me if this be false,” can there be question of a genuine oath.

If a priest asserts something upon his honor as a priest, he does not swear an oath, but simply affirms in a solemn manner.

Certain expressions in which the truth of an assertion is compared to the dogmas of religion, e. g., “It is as true as that there is a God in Heaven,” “I am as innocent as the Blessed Virgin Mary,” etc., are held by some theologians to be genuine oaths involving blasphemy; but we prefer to hold with Noldin that they neither constitute an oath, because God is not invoked as a witness, nor involve blasphemy (provided the assertion made is true), because the person who uses such an expression intends merely to assert a similarity between the certainty of his assertion and that of the revealed truth, not their equality. However, those who employ such phrases sin venially by taking the name of God in vain, and if the assertion made is false, they also commit objective blasphemy.

READINGS.—St. Thomas, Summa Theol., 2a 2ae, qu. 89, art. 3.—IDEM, Comment. in Sent., III, dist. 39, art. 1–3.—F. X. Linsenmann, Lehrbuch der Moraltheologie, pp. 450 sqq.—Thos. Slater, S.J., A Manual of Moral Theology, Vol. I, pp. 241 sq.—F. A. Göpfert, Der Eid, Mayence 1883, pp. 221 sqq.—H. Noldin, S.J., Summa Theol. Mor., Vol. II, pp. 257 sqq.—J. B. Ferreres, S.J., Comp. Theol. Mor., Vol. I, pp. 266 sqq.