Chapter IX — What truth is required in an assertory oath. The defect of even the smallest truth in this oath is a mortal sin. Some little questions concerning perjury are resolved

I. As has been said, truth is the chief of the conditions necessary for a lawful oath. It is not, however, necessary that this truth always be so in fact; but it suffices that the swearer, in good faith, believe the matter about which he swears to be true in his own mind. For it can happen that a matter is false, although it does not really stand thus, in the mind of the swearer; that is, metaphysical truth is not required, but moral truth. Wherefore truth is not taken so much from the object itself, or the matter sworn, as from the swearer himself — namely, that you swear the matter to be true, when, with sincere mind, you think it to be true, so that you swear without perjuring yourself. And, on the contrary, it can happen that you swear a false matter, and perjure yourself, because you think it to be false. So that I may resolve more clearly all the difficulties that can occur in the use of an assertory oath, I will present the following little questions with their responses.

II. Question I. Does one who swears falsely in the lightest matter sin mortally? Response: The Summa Angelica reports Godfrey teaching, in the chapter "Quod autem," that perjury in the lightest matter is a venial sin; which opinion Angles reckons probable, in these words (s.v. Perjurium): "It might, however, be said that a jesting lie is not, properly, a lie; and therefore he could hold that it is not properly perjury. But the safer opinion, according to the judgment of theologians, is otherwise." Antonio da Ignazio, in the Prolegomenon of Moral Theology of the Jesuits, ch. 1, and Henrique a Santo Ignazio, adjudge this same opinion, along with Bauny, in his Summa, p. 65, 15th edition, where he teaches it. And what Bauny says — as Godfrey's opinion, that one does not sin mortally, since it is not so great an irreverence as this — is proposition 24 among those condemned by Innocent XI, in these words: "To call God to witness to a light lie is not so great an irreverence as to warrant that one should be unwilling, or unable, to condemn a man for it." Domenico Viva, in his Theological Balance, interprets Bauny as admitting the smallness of matter only in a promissory oath. Let it be so. For I willingly interpret Catholic writers, as far as I can, in a sound sense along with the others. What I deny is that the proposition condemned by Innocent XI was, in its very words, conceived entirely in the sense of an assertory oath, not a promissory one. That the reason for the proscribed proposition does not hold, Fr. Viva himself testifies. Whatever the case may be, it is evident that the matter stands thus — since the malice of perjury does not derive its gravity from the lie, whether light or grave, whether jesting or pernicious, but from the irreverence, and supreme injury, which is done to God, whenever such matter of invocation, or the calling of God to witness of falsehood, occurs, whether it be the gravest, or the lightest.

For whoever invokes God, tacitly testifies that God can be deceived, or can deceive — and thus takes away from God his infallible truth. Therefore every perjury is a mortal sin. Indeed, the Angelic Doctor adds (II-II, q. 98, art. 3), where he establishes that every perjury is a mortal sin — he adds, I say, in his reply to the second objection, that perjury in a light matter is, in one respect, a graver sin than in a grave matter, and therefore, on the part of its own genus, a mortal one. He who perjures himself in jest does not avoid the divine irreverence, but in some respect increases it; and therefore is not excused from mortal sin. Only the defect of consideration, and of deliberation, or advertence, could excuse from mortal fault; but in such a case there would not be perjury — since the very reason for swearing requires deliberation, in the manner to be explained below. Here are the Angelic Doctor's own words: "He who swears falsely from a slip of the tongue, if indeed he adverts that he is swearing, and that what he swears is false, is not excused from mortal sin, any more than from contempt of God. If, however, he does not advert to this, he does not seem to have the intention of swearing; and therefore he is excused from the crime of perjury." Thus all authors teach, after Innocent XI condemned the aforesaid proposition.

III. Question II. Does one who swears a doubtful matter as certain, or, on the contrary, a certain matter as doubtful, sin mortally? Response: All the Doctors respond affirmatively. For one who swears a doubtful matter as certain, or a certain matter as doubtful, really lies: therefore he commits perjury, which is a mortal sin. You ought, then, to affirm or deny a matter in that manner in which you, all things prudently weighed, judge it to be. If the matter is doubtful to you, you ought only to declare it while doubting; if certain, you ought to declare it not doubtingly, but assertively.

IV. Question III. Does one who swears something by hyperbole, which, as it sounds, is not true, sin mortally? Response: Sánchez (Bk. III, on the Decalogue, ch. 4, n. 5), Tamburini (Bk. III, on the Decalogue, ch. 2, §1, n. 4), Leander (tract. 1, disp. 7, q. 7), Bonacina (disp. 4, q. 1, punct. 3, n. 6) respond negatively — since to say something false by a hyperbolic and figurative locution is not a lie, nor a sin. For this opinion they praise St. Augustine, and St. Thomas, who explains this in II-II, q. 111, art. 1. He recounts several sayings of Sacred Scripture which are explained by a figurative signification. In this manner is explained that saying of David (1 Kings 1): "Saul and Jonathan... were swifter than eagles, stronger than lions." That very many expressions of Sacred Scripture are explained by figurative and hyperbolic speech is well established. But that men who are neither Prophets nor Patriarchs, as those commonly were who are established from Scripture to have spoken figuratively, can confirm their hyperbolic assertions by oath, does not seem to me proven at all. For this reason, oaths of this kind, which Tamburini presses in the place cited — namely, "I swear that Peter possesses infinite riches," "that you are loved by me infinitely," "that your rivals are innumerable," etc. — since in the first place it is certain that such oaths are for the most part incautious, and consequently lack judgment, and are therefore illicit; moreover, an oath is granted by strictest right, and by way of medicine — therefore it is to be employed only when a grave illness, or necessity, presses.

V. Question IV. Is it lawful to swear something which you judge only probably to be true? Response: This little question is proposed by La Croix (Bk. III, part 1, ch. 70, n. 267). He responds in these words: "Sánchez (Bk. III, ch. 4, q. 2, dub. 3, n. 77) affirms this — since you swear this which you judge to be true; therefore you do not perjure yourself. Castropalao, part 5, n. 2, and others, in Diana, part 4, tract. 4, n. 10, extend this to swearing even in judgment. Some hold that one can lawfully swear a matter which he has heard from a notable and trustworthy man to be true. That which is probable, according to some, in Diana, is licit to swear even in judgment." Leander (tract. 1, disp. 8, near the end, p. 48), recalling to examination the kind of probability necessary for an oath, reports Tamburini as requiring a probability that induces moral certainty. But, reckoning this too rigid, he adds this: "But certainly any probability makes for moral certainty, as we have often said, with the common view." Whence... , as Palao well says, it will suffice, if he prudently judges, "according to a probable reason, that it is so." If you wish to know the principles of this doctrine, you must recall to memory the principles of probability, which Leander employs in their fullest amplitude. For he says that any probability whatsoever produces moral certainty, and that therefore any probable opinion whatsoever is a rule of honest action, and this is contained in that proposition condemned by Alexander VII, which stands in order 3: "Generally, whenever we act with either intrinsic or extrinsic probability, however slight, provided we do not depart from the bounds of probability, we always act prudently." This assertion, so indefinite, and generally set forth, Leander asserts of any probability whatsoever — whether grave, or slight — generating moral certainty, which anyone can prudently follow, as a rule of his own conscience, and this even in swearing. The Church has expressly condemned this. By a stronger right, then, that which Leander adds is to be execrated, namely, that anyone can swear a matter to be true which he judges only probable. Do not theologians commonly teach that God is called by oath to witness the truth? But, according to Leander, and those whom he cites, Sánchez, Diana, Castropalao, we will be able to invoke him as witness of probability! How can we swear that something is true which is not true, but only probable to us? For "true" is opposed to "false," and "probable" is opposed not to "false," but to "improbable." Since, then, contrary probable reasons occur most frequently concerning the same matter, anyone will be able, by oath, to affirm the same matter, and also, by oath, to deny it. According to the Probabilists, one can, from probable opinions, follow whichever one prefers, and now embrace, now reject, the same one. Or at least one will be able to select whichever part is to be affirmed or denied by oath, whichever has seemed more opportune, and more accommodated to his own affairs. All of which not only betrays laxity, but even strikes horror. If Leander, with the authors he adduces, had said that one can swear a matter which he knows to be probable, as probable, it would somehow seem tolerable. But, since they assert that one can swear as true what we merely judge probable, and moreover that any probability whatsoever can induce moral certainty, we can in no way admit this. Wherefore we reject Leander's opinion as false.

The opinion, however, which Fr. La Croix reports from Sánchez and others, we reject as improbable — since what we know only by probable conjecture, as Sánchez himself says, we cannot affirm as true, but as probable. For the common opinion of theologians is that the matter of an oath is truth, considered not absolutely, and as it is in reality, but in the manner in which it is perceived by the intellect. Therefore, if the swearer knows the matter as probable, he cannot swear it as true; and if he does not know it as true, he cannot swear it as merely probable. What they further add — that for an oath to be given in judgment, moral certainty is required, but that in other private oaths probable certainty suffices — this, as I judge, is a mere fabrication. For the reasoning is the same for a private, as for a public, oath: for the same is the formal reason which is attributed to each species — namely, the invocation of divine testimony in confirmation of truth. The same certainty, therefore, is necessary for both oaths, whether in judgment, or outside judgment. One who knows a matter as probable cannot swear it as true, but as probable, and conversely. It is indeed true that, according to the decrees of the laws, in judgment, testimonies are not admitted except of those things of which the witness has evidence, that is, unless he is a witness from having seen with his own eyes; and consequently a knowledge of the truth wholly evident is necessary. For the rest, whatever positive law may prescribe, in every oath, whether public or private, moral certainty is necessary — which we shall explain in the following little question.

When, however, someone confirms by oath a probable knowledge which he has of some matter, the matter of the oath is not the probability, or the doubt itself, but the truth of the probability and of the doubt: for, when I swear that I either opine, or doubt about some matter, I swear the truth — because it is really true that I have such an opinion, or doubt, or suspicion.

VI. Question V. What certainty is required, in order for someone to be able to swear licitly? Response: For a clearer, and fuller, understanding of the preceding question, I have proposed to settle this little question. There is one certainty which is evident, and metaphysical; another, experimental; another, moral; another, probable, which admits various degrees. Very many recent theologians and Casuists teach that a knowledge which is verisimilar, or probable, concerning some matter, suffices for someone to be able to swear. Thus teach, besides those cited in the preceding number, the theologians of Salamanca (tract. 17, ch. 2, punct. 3, §1), who praise Candido, Lessius, Azor, and others. This opinion does not at all convince me, and, according to the adversaries' own principles, seems to me false. For, if they themselves teach that a probable opinion produces moral certainty, and that we can choose, between two opinions on the same matter, whichever we reckon more opportune for ourselves — it certainly follows that we too will be able, by oath, to confirm or deny the same matter, according as time and our own reasons shall demand. How false, and erroneous, this is, no one fails to see.

VII. Rejecting, then, this opinion, we say, first, that indeed a mathematical, and altogether evident, certainty is not always required in an oath — since this cannot be had in very many cases; but we assert that a moral certainty is necessary, which excludes every prudent doubt. This moral certainty, however, is in no way induced by conjectures, and merely probable and verisimilar reasons — since the adversaries themselves flee to reflex principles, so that these merely probable reasons may not remove this doubt. But most weighty foundations, and reasons, are necessary, which render us certain concerning the matter about which we must swear. This opinion of ours is clearly drawn from the Catechism of the Council of Trent, Part III, on the second commandment of the Decalogue, §2: "The first thing, then, that is required in an oath is truth — namely, that what is asserted be true, and that the one who swears judge it so to be, not rashly, nor led by any light conjecture, but by the most certain arguments." This same thing is taught by Cardinal Bellarmine (Bk. I, on the Sacraments in general, ch. 16): "Even though one has a probable reason for believing, he nonetheless does not have certainty; for it can happen that he thinks he believes, and yet does not really believe. But certainty is required for testifying, that is, in the name of God; nor does a probable opinion suffice, as is clear in the similar case of an oath."

To witness truly, and to swear well, is not lawful, except for one who can know what he swears. No one swears well unless he can say, 'I have sworn... and I will keep it, to judge the justice of thy testimonies' — that is, unless he has certainty. For nor does a probable opinion suffice, just as a probable opinion does not suffice for testifying by oath; but only in a matter of which we are most certain. This opinion can be confirmed by what St. Ambrose writes (on Psalm 118, sermon 14, n. 14): "The voice of one walking in light." To say, "I swore," is a testimony of knowledge... Let it not be permitted, then, to swear except concerning matters of which we are most certain. Let no one swear who does not know what he swears... To swear, then, is a judgment of knowledge and of conscience... Let light go before you, if you intend to swear — that is, let the knowledge of the truth go before you, so that the bond of the oath may not harm you.

VIII. It is true, however, that the adversaries too admit that moral certainty is necessary; but in this they fail, that they teach that this moral certainty can be had by merely verisimilar conjectures, and merely probable reasons. For even granting that a probable opinion produces so much certainty as suffices as a rule of honest action, it does not, for that reason, follow rightly that it produces so much certainty as suffices for swearing that to be true which we opine to be only probable. For a greater certainty is required for an oath than for any moral opinion whatsoever. For this latter, mere true probability suffices to be a rule of honest action. But when someone swears something as true, it is not enough that it be probable; it is required that it appear true to the swearer — not through merely probable reasons, but through most weighty principles, or arguments, and certain ones. When this certainty is lacking, and only conjectures and probable reasons appear, then the swearer ought to affirm, or deny, a matter as probable, not as true.

IX. Question VI. What certainty is required for an oath to be tendered in judgment? Response: In the forum, certain knowledge is necessary... ; testimonies from hearsay are not admitted there, since witnesses there must have evidence from sight. More recent theologians commonly teach, the theologians of Salamanca, Sporer, La Croix, and many others whom they cite, that a witness worthy of credence suffices for swearing outside judgment; not so in judgment. When someone swears concerning another's deed, they say, experimental knowledge is necessary, such as is had by sight; but that a single credible witness suffices outside judgment, not so in judgment.

But it seems to me that it must be said that, whether in judgment or outside judgment, no one can swear a matter as true which he has heard only from a single witness, even a trustworthy one; but he must swear it in the manner in which he knows it — namely, either because he has had it established by his own eyes, or because he has received it by report from others. Although a trustworthy witness may be a foundation for me to believe prudently what he relates, this faith, or credulity, cannot be of such authority to me that, relying on it, I could absolutely swear that what I have heard is true; but I can only swear that I have heard it. Why can we not swear before a judge, absolutely, that what we have heard from a single witness is true? For no other reason, surely, than that a single human witness does not induce certainty sufficient for an oath. And although in judgment the discussion concerns the harm of one's neighbor, nonetheless such a great certainty is demanded in judgment, not so much to avoid the harm of anyone, as so that every occasion of perjury may be removed. This is the peculiar thing that occurs to be said concerning judicial oaths — namely, that judges, in pronouncing sentence, ought to exact such oaths as are established by the testimony of the eyes concerning that which is affirmed — namely, oaths of experimental, as it is called, certainty.

It is false, then, what more recent theologians commonly assert — that, outside judgment, one can absolutely swear something to be true which he knows only through probable reasons and conjectures; but, whether in judgment or outside it, you are able to swear what you know: and what you know only by hearsay, you ought to swear by hearsay; and what is established to you by sight, you ought to swear is established to you by sight. The reason for this is that, whether in judgment or outside it, the formal reason of the oath is the same — namely, the invocation of divine testimony; and the same reverence is owed to God everywhere and always. This, however, is the distinction between judicial and private oaths: that a judge decides nothing, unless witnesses swear a matter established by sight; private men, however, more often give credence to, and deliberate much upon, oaths concerning things heard (especially where the harm of a third party is not at issue). Wherefore, if you swear to me that you heard from a most trustworthy man, subject to no exception, that some deed occurred, I, as a private man, would give it full credence; and, insofar as such knowledge concerned my affairs or business, I would use it as a rule for many of my deliberations; but, as a judge, I would have no faith in you, nor would I decree anything relying on such an oath.

X. Question VII. What diligence is required in inquiring into the truth necessary for an oath? Response: The theologians of Salamanca (loc. cit., n. 4) answer in these words: "Equal diligence is not required in every matter to scrutinize the truth of the thing sworn; but, according to the condition of the greater or lesser weight of the thing, greater or lesser diligence is to be employed. For in matters of greater weight, greater care is to be employed than in matters of lesser moment."

This rule seems to me false. Since it is not the nature of the thing sworn, but the supreme gravity and dignity of the oath itself, that ought to be the norm of the diligence necessary in the inquiry of the truth before one swears. Is not assertory perjury, even in the lightest matter, a mortal sin? Why? Because the gravity of perjury is derived not from the matter sworn, but from the injury done to divine truth. Therefore, since an oath, by its own nature, with no regard to the matter sworn, is, among all peoples, a matter of the highest moment, the utmost diligence for the inquiry of truth ought to precede it. Only, then, can it be said that greater or lesser diligence is to be employed with respect to the truth itself, insofar as the matter which is sworn is more or less accessible and open to view, not with respect to the matter sworn. When, however, the matter sworn is grave in weight, since it concerns the reputation, or fortune, of one's neighbor, greater diligence and deliberation is required, not by force of the oath, or of the virtue of religion, but by force of another virtue, of justice, or of charity — since, if you swear falsely against your neighbor in a grave matter, besides perjury you commit the sin of injustice. And it is in this sense that it is said that, when the matter sworn is of great weight, grave diligence is also required on this ground, so that, besides perjury, the sin against justice may be avoided. All this seems certain to me, and cannot be denied even by more recent authors, though they assert the contrary in ambiguous words.

XI. Question VIII. Does one who is notably negligent in inquiring the truth of the matter he swears sin mortally, even though it happens that the matter he swears is true? Response: Sánchez (Bk. III, on the Decalogue, ch. 4, n. 10), Leander (tract. 1, disp. 7, q. 1), and, in them, Scotus, Cajetan, Richard, Sotus, Navarrus, and commonly all Doctors teach that this person sins mortally — since he exposes himself to the danger of perjury, and omits the necessary diligence in a matter of grave weight.

But, so that all that has been said in the preceding little questions may be more validly confirmed, and especially that rule in which we said that probable knowledge, which can suffice for governing other human acts, by no means suffices for the making of an oath, it is worth bringing forward St. Thomas's teaching. The holy Doctor, then, has this (II-II, q. 89, art. 3, ad 3): "There is great danger in an oath, both on account of the greatness of God, whose testimony is invoked, and also on account of the fickleness of the human tongue, whose words are confirmed by the oath. And therefore such things (namely, truth, judgment, justice) are more required for an oath than for other human acts."

XII. Question IX. Can it be lawful — as the Scholastics call it — to swear that one saw a fellow student attend classes for the time required by the university for completing his course, if it suffices that they have commonly seen him frequent the schools? Response: Tamburini (Bk. III, ch. 2, §1, n. 8) relates this case from Hurtado, in Diana, Part V, tract. 8, resol. 10. A student, wishing to prove attendance, for which he needs two witnesses, can employ two friends who did not see him present at the lectures, but who are sufficiently persuaded that he was present; but they cannot swear that they saw it. Tamburini approves this decision, to which I in no way can accede. For this resolution is quite involved, and entangled. Why can they not swear that they saw him, but can absolutely swear that he frequented the schools? Because they are sufficiently persuaded that he was present at the lectures. Why so? No ground of that persuasion is adduced. Wherefore it seems to be implied that these two student friends did not at all see him, and yet can freely and absolutely swear that they saw him attend classes, or that the student himself testifies to it, or that they themselves, kindly and out of a certain inclination toward their student friend, have been persuaded that he really did frequent the schools. But no one fails to see that these foundations are by no means sufficient for making the oath that the student attended lectures — for, in order for the aforesaid friends to be able to swear this in good faith, it is necessary either that they themselves saw him, or that they have as witnesses persons worthy of credence who affirm this. What authors commonly teach afterward — that, for this oath to be given without fault, it is not necessary that the swearers should have seen the student go to school every single day — is true, since such knowledge cannot be had by due diligence. It will suffice, then, for them to know that the student commonly attended the lectures; for this is what universities require, and no more — although, so that the oath may be pronounced with due religion, the swearers ought to confirm by oath a common, not a daily, presence in the schools. Extremes are nonetheless to be avoided. When an oath is made according to the mind of the one questioning, truth, judgment, and justice accompanying it in good faith, one must beware of excessive anxiety, and superstition, lest, while you strive to avoid one extreme, you fall into the other.

XIII. Question X. Is it lawful to persuade someone to swear a truth of which he himself is ignorant? Response: It is certain among all that this is not lawful — since one who swears without certain knowledge sins mortally; therefore one who induces him to swear in this manner, without certain knowledge, similarly sins. For the clarity of this matter, this case is usually proposed. Peter, a merchant, to prove that Paul owes him a hundred gold pieces, which he really does owe, but which Paul otherwise denies owing, induces Anthony to swear the truth of this debt — namely, that Paul owes Peter a hundred gold pieces — although it is false that Anthony has this knowledge. Anthony swears. His oath, then, is certainly perjury. He is not, however, bound to restitution, since the debt of a hundred gold pieces is supposed to be true. And although Peter the merchant produces reasons which seem to him... seem true, you cannot for that reason swear in judgment that you know it; nor even outside judgment; but you can only swear that you have heard from Peter that this sum of money is owed him by Paul.