§ 2. On the Lawfulness of an Oath and Its Requisite Conditions

439. Many have denied the lawfulness of an oath. Already the Pelagians and Messalians⁵¹⁹ seem to have denied the lawfulness of an oath. They were followed by the Waldenses,⁵²⁰ Beguines and Beghards, Fraticelli, Wycliffe,⁵²¹ the Hussites,⁵²² Anabaptists, Mennonites, Quakers,⁵²³ and others. Among philosophers, Kant and Fichte fought against the lawfulness of an oath. Against all these is set down:

Thesis. An oath clothed with the due conditions is lawful and licit.

⁵¹⁹ Cf. St. Augustine, Ep. 156 (al. 88); Sermon 180, c. 10, n. 11.

⁵²⁰ The following profession of faith was prescribed to the Waldenses: "We do not condemn an oath; indeed, we believe with a pure heart that it is lawful to swear with truth and judgment and justice" (Denz., n. 425; cf. also n. 487).

⁵²¹ Cf. proposition 43 condemned by the Council of Constance (Denz., n. 623).

⁵²² Cf. "Questions to Be Proposed to Wycliffites and Hussites," nn. 12-14 (Denz., nn. 662-664).

⁵²³ Cf. concerning all these errors Göpfert, Der Eid, 112ff. Since the Mennonites so abhor the taking of an oath, the civil laws of Germany have permitted them to employ other formulas confirming the truth to be spoken in place of an oath. Cf. Z.P.O. § 484.

440. Proof 1. From Sacred Scripture, which often acknowledges the lawfulness of an oath, e.g.: "Thou shalt fear the Lord thy God and shalt serve Him alone, and shalt swear by His name."⁵²⁴ St. Paul himself swore several times: "For God is my witness, whom I serve in my spirit";⁵²⁵ "But I call God to witness."⁵²⁶ But if Christ⁵²⁷ and James seem to reprove every oath, they are to be understood concerning an unlawful oath, or one not clothed with the due conditions. For St. Paul certainly knew the words of Christ, and nevertheless he himself swore several times. St. Augustine⁵²⁸ writes excellently on this matter: "Because it is impious to say that Paul was guilty of violating the precept, especially in epistles composed and published for the spiritual life and salvation of peoples, it must be understood that the word 'altogether' was placed for this purpose: that, insofar as it lies in thee, thou shouldst not seek, love, or desire an oath as though it were a good with some delight; ... namely, lest by swearing one come to readiness in swearing, and from readiness to habit, and from habit fall into perjury."

Proof 2. From the practice and doctrine of the Church. No one denies that the oath has always been employed in the Church as well as in the civil commonwealth. The doctrine of the Church on this matter is found in several decisions against the Waldenses, Wycliffites, Hussites, Quesnel, and the Synod of Pistoia, cited above in the preceding number.

Proof 3. From reason. An act whose origin and end are good is lawful in itself. But an oath is such. For an oath proceeds from faith in God as omniscient and as avenger of justice; but the end of an oath is to terminate controversies, obtain the full truth, and confirm promises. Therefore an oath clothed with the due conditions is something lawful and is an act of religion.⁵²⁹

But although an oath is lawful and licit in itself, nevertheless it is not to be sought for its own sake or employed too frequently, since otherwise abuses easily creep in.⁵³⁰ Because of these abuses, certain Holy Fathers spoke more severely concerning the oath, especially St. John Chrysostom and St. Jerome.⁵³¹ Therefore it is also said in Sacred Scripture: "Let not thy mouth be accustomed to swearing; for in it there are many falls.... A man that sweareth much shall be filled with iniquity, and a scourge shall not depart from his house. And if he make it void, his sin shall be upon him; and if he dissemble it, he offendeth double; and if he swear in vain, he shall not be justified."⁵³² The intrinsic reason is that an oath is, as it were, a medicine against the defect of human veracity and credibility. For if every man were always truthful, so that full faith could be given to his assertions, an oath would already be superfluous. Moreover, an oath can easily introduce a danger of sinning, since all the conditions required for its lawfulness are often absent. Therefore it is clear that an oath is not to be sought for its own sake, just as a man does not seek medicine except in a case of necessity.

Conditions required for a valid and lawful oath.

For a valid oath two conditions are required, namely: 1. the intention of swearing; and 2. an oath-formula. For a lawful oath, moreover, three conditions are required, namely: 1. truth; 2. justice; 3. judgment.

⁵²⁴ Deut. 6:13.

⁵²⁵ Rom. 1:9.

⁵²⁶ 2 Cor. 1:23; cf. also Phil. 1:8; Heb. 6:13-18.

⁵²⁷ "You have heard that it was said to them of old: Thou shalt not forswear thyself, but thou shalt perform thy oaths to the Lord. But I say to you not to swear at all.... But let your speech be yea, yea; no, no; and that which is over and above these is of evil" (Matt. 5:33ff., 37). St. James teaches the same: "But above all things, my brethren, swear not, neither by heaven, nor by the earth, nor by any other oath whatsoever. But let your speech be: yea, yea; no, no; that you fall not under judgment" (James 5:12).

⁵²⁸ De mendacio c. 15, n. 28 (Migne, Patr. lat. 40, 507).

⁵²⁹ Cf. S. theol. 2, 2, q. 89, a. 2.

⁵³⁰ Cf. ib., a. 5.

⁵³¹ There is no space to explain the texts of the Holy Fathers who apparently rejected the oath; for it is certain that the same Holy Fathers sometimes themselves declared an oath lawful. See Billuart, De relig. diss. 5, a. 3.

⁵³² Ecclus. 23:9, 12ff.

441. A. Conditions required for a valid oath:

1. An internal intention of swearing (whether actual or at least virtual) is altogether necessary for the validity of an oath; therefore, the external and material pronouncement alone of an oath-formula is not a true but a feigned oath. A feigned oath, however, seems to be a grave sin⁵³³ (at least if it is done freely and deliberately), since it is a grave injury inflicted upon God, who is dishonored by a deceitful invocation and is induced to deceive those hearing the oath. Hence proposition 25 was condemned by Innocent XI: "With a cause it is lawful to swear without the intention of swearing, whether the matter is light or grave."⁵³⁴ Hence those who freely take the oath-formula in a tribunal but inwardly withhold the intention of swearing do not escape the penalties of perjury either before God or before men. For a true and sufficient intention of swearing, it is required that the one swearing know what an oath is and that he have sufficient deliberation both concerning the act itself of swearing and concerning the matter of the oath. Because of a defect of a true intention of swearing, very many confirmatory formulas customarily used in human conversations are not true oaths; e.g., I assert this by my faith, by my honor, by my conscience; these things are as true as the light of the sun, as the existence of God; may the devil seize me if this is false, etc. Certainly these and similar formulas of speech signify that the speaker intends a great confirmation of his assertion, but it is by no means certain whether he really wills to invoke God as witness. The faithful are to be admonished to abstain from locutions of this kind as vain and indeed often sinful. "Let your speech be: yea, yea; no, no"; thus the Lord admonishes. In the external forum a true intention of swearing is always presumed when a true oath-formula has been pronounced.

⁵³³ If certain authors call a freely made feigned oath a venial sin or even no sin, they either teach falsely or take a feigned oath in the broader sense, insofar as it is a mere vain assumption of the name of God.

⁵³⁴ Denz., n. 1175.

442. 2. An oath-formula is required for the validity of an oath, because it must be an external sign for confirming the assertion made. This formula necessarily contains an explicit or at least implicit invocation of God, since the invocation of God as witness to the truth pertains to the essence of an oath. In ecclesiastical law the oath-formula customarily employed is: "So may God help me and these holy Gospels of God." In civil laws also, determinate formulas are customarily prescribed; if neither in themselves nor from the intention of the legislator they contain an invocation of God, they are not true religious oaths.⁵³⁵ In private oaths no determinate formula is required, but it suffices that someone intend by signs or words to invoke the divine name in testimony to the truth; indeed, an oath could be made to God Himself by an internal act, e.g., someone, in order that he may will firmly to avoid some occasion of sin, internally invokes God as witness.

⁵³⁵ Thus, e.g., the formula employed by the Mennonites, "I swear by the truthfulness of a man," is not a religious oath.

443. Scholion. On rightly understanding oath-formulas. Authors customarily weave here a rather long list of formulas of explicit or implicit oaths; likewise, they present several ambiguous formulas, or formulas certainly containing no oath. These seem to be of little utility, both because the validity of an oath, although not solely, nevertheless principally, depends upon the intention of the speaker, and because in diverse regions these formulas are understood differently. Let the following be noted briefly:

a) Formulas of speech in which God is explicitly or implicitly invoked as witness to the truth are true oaths, objectively speaking; e.g., "May God be my witness"; "I swear by God, by Christ"; "I swear by the Blessed Virgin, by the Cross, by the Gospels, by my soul," etc. But subjectively speaking, these or similar formulas of speech are sometimes to be regarded as a true oath neither from the intention of the speaker, who pronounces them without any serious deliberation and from inveterate habit, nor from their understanding by the hearers. For if someone confirms almost every assertion of his by exclaiming, "It is so, by God!"⁵³⁶ this manner of speaking is certainly to be reproved seriously as an intolerable abuse of the name of God; but neither the speaker himself nor the hearers think that every assertion thus confirmed is an oath.

b) Formulas in which God is neither explicitly nor implicitly invoked as witness are not an oath. Hence, if someone should say, "By my conscience, by my honor"; or if a priest should say, "By my consecration"; or if a prince should confirm his word, "By my royal honor," he does not indeed make a religious oath; nevertheless, these or similar formulas of speech are customarily regarded as such great confirmations of truth that their violation is considered truly base and scandalous.

c) Formulas by which the truth of an assertion is compared with truths of faith are not themselves an oath either. Hence the formulas, "This is as true as God exists; as Christ is in the venerable Sacrament; I am as innocent as the Blessed Virgin," etc., do not contain an oath, since they are not invocations of God's testimony; nor are they blasphemies, since the speaker is not accustomed to intend that his assertion have the same certainty as the truth of faith stated.⁵³⁷ But it is clear of itself that locutions of this kind are to be avoided altogether.

⁵³⁶ "By God, that is true!"

⁵³⁷ Cf. St. Alphonsus, Theol. mor. l. 3, n. 137.

444. B. Conditions required for a lawful oath.

For a lawful oath three conditions are required, already enumerated above, which are customarily called the companions of an oath,⁵³⁸ and which are already indicated by Jeremiah: "Thou shalt swear: The Lord liveth, in truth and in judgment and in justice."⁵³⁹ If even one of these conditions is absent, an oath lacks due reverence toward God and consequently is unlawful.

1. The truth of an oath does not signify the objective truth of the assertion made, but the veracity of the speaker, who does not speak contrary to his mind, or who does not tell a moral lie. This truth, therefore, presupposes a firm will to speak the truth (in an assertory oath) or to fulfill what is promised (in a promissory oath). Truth is the principal companion of an oath; if it is absent, there is the very grave sin of perjury, concerning which the discourse will return below in n. 456ff. But it is required not only that the one swearing avoid every moral lie, but also that he have moral certainty concerning the things asserted. Hence it is not lawful to swear either with doubtful truth or with merely probable truth. Likewise, it is never lawful to swear with a purely mental restriction. Thus holds the most common opinion, which is corroborated by the condemnation of propositions 26 and 28 pronounced by Innocent XI.⁵⁴⁰ But to swear with a broadly mental restriction is not lawful except for a grave cause; namely, in the case in which no other means is at hand to defend oneself or others against an unjust aggression, an unjust manner of questioning, or another grave evil. Thus a confessor who is unjustly compelled to give sworn testimony concerning things which he learned under the seal of confession can, and indeed must, swear with a mental restriction.

It is asked how great a sin it is to swear without sufficient cause with a broadly mental restriction. Many authors teach that such an oath is a mortal sin, since it is a grave irreverence against God to employ the invocation of His name to deceive others. St. Alphonsus⁵⁴¹ admits this doctrine concerning an oath in a trial or in contracts, but thinks it more probable that it is only a light sin if someone without sufficient reason employs a broadly mental restriction in other private oaths, because truth is not absent in such an oath, since the words pronounced can easily be understood in a right sense; nor is justice absent, because the questioner has no right, as is supposed, to a simple answer without restriction. Therefore only the third companion of an oath, namely judgment or discretion, is violated, and its violation is only a light sin. Although these things are true, nevertheless in practice this case seems scarcely possible. For it has already been prohibited that anyone swear without necessity or a grave reason. Therefore it is prohibited much more severely that anyone swear without necessity with a mental restriction.

⁵³⁸ Eidesgefährten [companions of an oath].

⁵³⁹ Jer. 4:2. Cf. also S. theol. 2, 2, q. 89, a. 3.

⁵⁴⁰ Cf. what was said above in n. 171 concerning mental restriction.

⁵⁴¹ St. Alphonsus, Theol. mor. l. 3, n. 151.

445. 2. Justice as the second companion is required in both an assertory and a promissory oath; it consists in this, that the one swearing neither asserts nor promises anything that is unlawful.

In an assertory oath, justice requires that no one unduly injure the reputation of another, e.g., by manifesting without sufficient cause the occult crime of another; that no one injure his neighbor in fortune; and that no one boast of a crime he himself has committed. A violation of justice in an assertory oath is a sin whose gravity depends a) upon the gravity of the injustice committed, and b) upon the intention of the one swearing. Hence it seems to be a mortal sin if someone, e.g., uses an oath as an instrument for proving a grave detraction,⁵⁴² because one who thus invokes God as witness represents Him, as it were, as an assistant in his crime. Almost the same seems to be said (although certain persons, e.g., Göpfert, contradict it) if someone for the sake of boasting confirms by an oath a narrative of his own grave sins. Nevertheless, in practice one must first see whether a true oath was present in these locutions; for often neither does the locution itself contain an invocation of the name of God, nor does the speaker have the intention of invoking God as witness to his sin.

In a promissory oath, justice requires that the one swearing promise nothing evil. Hence he who swears that he will perpetrate some grave crime (e.g., adultery, homicide, etc.) certainly commits a twofold grave sin: one sin offends the virtue which he intends to violate; the other sin is a grave violation of the virtue of religion, because the one swearing invokes God, almost mockingly, as witness that he wills to offend Him gravely. Thus all teach. But if the oath concerns the doing of a slightly evil thing, e.g., concerning a lie or a slight deception, certain grave authors, such as Dominic Soto,⁵⁴³ Cajetan,⁵⁴⁴ Sylvius,⁵⁴⁵ Busenbaum,⁵⁴⁶ Noldin,⁵⁴⁷ etc., judge that it is only a venial sin, because it is only a slight irreverence toward God. Other authors, however, such as St. Alphonsus,⁵⁴⁸ Billuart,⁵⁴⁹ Tanquerey,⁵⁵⁰ Göpfert,⁵⁵¹ etc., think that in this case also a grave sin is committed, because it seems to be a grave injury inflicted upon God to invoke Him as witness and, as it were, patron of even venial iniquity. For it seems to be contempt and mockery of God (who abhors all sins, even light ones) if a man, willing to commit a light sin, confirms his depraved intention by invoking divine testimony.

You resolve: From what has been said follows the solution of the following cases: 1. A certain Freemason swears that he will persecute the Church. There are certainly two mortal sins, namely, the persecution of the Church and a sacrilegious oath. 2. Someone swears that he will tell a jocose lie. There are two sins, namely, the light sin of a jocose lie and the perhaps grave sin of a sacrilegious oath. Rarely, however, do confirmatory formulas concerning a future venial sin to be committed have the character of a true oath, because of a defect of intention both in the one who speaks and in those who hear the speaker. Hence the first opinion, although considered theoretically it is less true, nevertheless can be held in practice.

Theologians commonly teach that it is only a light sin if someone swears to omit some good act which is counseled but not commanded, e.g., not to enter religion, not to give alms outside a case of necessity. Concerning this case the Angelic Doctor⁵⁵² says: "But if someone swears that he will not do some better good which nevertheless he is not bound to do, he sins indeed by swearing, insofar as he places an obstacle to the Holy Ghost, who is the inspirer of a good resolution; nevertheless, he does not sin by keeping the oath, but does much better if he does not keep it."

⁵⁴² Cf. St. Alphonsus, Theol. mor. l. 3, n. 146.

⁵⁴³ De iure et iust. l. 8, q. 2, a. 3, concl. 5.

⁵⁴⁴ Commentary on 2, 2, q. 89, a. 7.

⁵⁴⁵ Commentary on the same place.

⁵⁴⁶ In St. Alphonsus, l.c., n. 146.

⁵⁴⁷ De praeceptis, n. 255.

⁵⁴⁸ L.c.

⁵⁴⁹ De relig. diss. 5, a. 4.

⁵⁵⁰ De virt. relig. n. 951.

⁵⁵¹ Moraltheol. I, 355.

⁵⁵² S. theol. 2, 2, q. 89, a. 7 ad 2.

446. 3. Judgment (Besonnenheit, deliberateness) as the third companion of an oath requires due discretion, so that there be a) a just cause for swearing; b) due reverence in the act itself of swearing. A defect of this companion ordinarily is only a venial sin, provided, however, that the other two companions of an oath are present.

The reason is that the whole malice of a defect of judgment consists in this, that divine testimony is invoked vainly and superfluously, or not sufficiently reverently; this of itself does not seem to exceed venial guilt.⁵⁵³ Therefore those sin of themselves only venially who swear frequently without necessity, who swear jocularly, or who swear with insufficient reverence. But accidentally a defect of judgment in an oath can be a grave sin, namely, if grave scandal or a proximate danger of sinning against the truth or justice of the oath arises from it.⁵⁵⁴ Since a defect of judgment is so often present in oaths and introduces so many dangers of sin, Christ, St. James, St. John Chrysostom, and St. Jerome commended not swearing at all.⁵⁵⁵

⁵⁵³ Cf. Billuart, De relig. diss. 5, a. 4.

⁵⁵⁴ Fahrlässiger Meineid [negligent perjury].

⁵⁵⁵ Cf. the texts cited above in n. 440, and Göpfert, Der Eid, 61ff.

447. Scholion. Who can swear. By natural law every rational creature using reason, whether angel or man, whether having reached puberty or not, and even Christ Himself as man, can swear. The reason is that all creatures can confirm their statements by invoking divine testimony. If God Himself is at times introduced in Sacred Scripture as swearing, this is not an oath properly so called, because no one can invoke himself as witness to the truth; and especially it is not done as though the divine words needed confirmation, but such oaths show the immutability of God.⁵⁵⁶

By ecclesiastical law, several persons are not admitted to a solemn oath, e.g., those who have not reached puberty, infamous persons, and those who have already been convicted of perjury.⁵⁵⁷ Clerics ought not swear in a lay tribunal unless the prior permission of the bishop or legitimate prelate has been obtained.⁵⁵⁸ Priests, by reason of their dignity, ought not swear even in an ecclesiastical trial except for a grave cause, because to doubt their veracity is to derogate from their state.⁵⁵⁹

By civil laws, those who have not yet completed sixteen years are not customarily admitted to a judicial oath.⁵⁶⁰ Likewise, several others are excluded. Others, on the contrary, can refuse an oath. Concerning all these things, as pertaining solely to ecclesiastical or civil law, there is no space to treat more extensively here.

⁵⁵⁶ S. theol. 2, 2, q. 89, a. 10 ad 4.

⁵⁵⁷ Code of Canon Law, c. 1757.

⁵⁵⁸ Holy Office, decree of 23 Jan. 1886, and Code of Canon Law, c. 120.

⁵⁵⁹ S. theol., l.c., a. 10.

⁵⁶⁰ Cf. German Code of Civil Procedure, § 435, and Code of Criminal Procedure, § 56.