On the contrary, It is written ( Dt. 6:13 ): "Thou shalt fear the Lord thy God . . . and shalt swear by His name."
I answer that, Nothing prevents a thing being good in itself, and yet becoming a source of evil to one who makes use thereof unbecomingly: thus to receive the Eucharist is good, and yet he that receives it "unworthily, eateth and drinketh judgment to himself" ( 1 Cor. 11:29 ). Accordingly in answer to the question in point it must be stated that an oath is in itself lawful and commendable. This is proved from its origin and from its end. From its origin, because swearing owes its introduction to the faith whereby man believes that God possesses unerring truth and universal knowledge and foresight of all things: and from its end, since oaths are employed in order to justify men, and to put an end to controversy ( Heb. 6:16 ).
Yet an oath becomes a source of evil to him that makes evil use of it, that is who employs it without necessity and due caution. For if a man calls God as witness, for some trifling reason, it would seemingly prove him to have but little reverence for God, since he would not treat even a good man in this manner. Moreover, he is in danger of committing perjury, because man easily offends in words, according to James 3:2, "If any man offend not in word, the same is a perfect man." Wherefore it is written ( Ecclus. 23:9 ): "Let not thy mouth be accustomed to swearing, for in it there are many falls."
Reply to Objection 1: Jerome, commenting on Mat. 5:34, says: "Observe that our Saviour forbade us to swear, not by God, but by heaven and earth. For it is known that the Jews have this most evil custom of swearing by the elements." Yet this answer does not suffice, because James adds, "nor by any other oath." Wherefore we must reply that, as Augustine states (De Mendacio xv), "when the Apostle employs an oath in his epistles, he shows how we are to understand the saying, 'I say to you, not to swear at all'; lest, to wit, swearing lead us to swear easily and from swearing easily, we contract the habit, and, from swearing habitually, we fall into perjury. Hence we find that he swore only when writing, because thought brings caution and avoids hasty words."
Reply to Objection 2: According to Augustine (De Serm. Dom. in Monte i. 17): "If you have to swear, note that the necessity arises from the infirmity of those whom you convince, which infirmity is indeed an evil. Accordingly He did not say: 'That which is over and above is evil,' but 'is of evil.' For you do no evil; since you make good use of swearing, by persuading another to a useful purpose: yet it 'comes of the evil' of the person by whose infirmity you are forced to swear."
Reply to Objection 3: He who swears tempts not God, because it is not without usefulness and necessity that he implores the Divine assistance. Moreover, he does not expose himself to danger, if God be unwilling to bear witness there and then: for He certainly will bear witness at some future time, when He "will bring to light the hidden things of darkness, and will make manifest the counsels of hearts" ( 1 Cor. 4:5 ). And this witness will be lacking to none who swears, neither for nor against him.
Whether three accompanying conditions of an oath are suitably assigned, namely, justice, judgment, and truth?
Objection 1: It would seem that justice, judgment and truth are unsuitably assigned as the conditions accompanying an oath. Things should not be enumerated as diverse, if one of them includes the other. Now of these three, one includes another, since truth is a part of justice, according to Tully (De Invent. Rhet. ii, 53): and judgment is an act of justice, as stated above (Q[60], A[1]). Therefore the three accompanying conditions of an oath are unsuitably assigned.
Objection 2: Further, many other things are required for an oath, namely, devotion, and faith whereby we believe that God knows all things and cannot lie. Therefore the accompanying conditions of an oath are insufficiently enumerated.
Objection 3: Further, these three are requisite in man's every deed: since he ought to do nothing contrary to justice and truth, or without judgment, according to 1 Tim. 5:21, "Do nothing without prejudice," i.e. without previous judgment [*Vulg.: 'Observe these things without prejudice, doing nothing by declining to either side.']. Therefore these three should not be associated with an oath any more than with other human actions.
On the contrary, It is written ( Jer. 4:2 ): "Thou shalt swear: As the Lord liveth, in truth, and in judgment, and in justice": which words Jerome expounds, saying: "Observe that an oath must be accompanied by these conditions, truth, judgment and justice."
I answer that, As stated above (A[2]), an oath is not good except for one who makes good use of it. Now two conditions are required for the good use of an oath. First, that one swear, not for frivolous, but for urgent reasons, and with discretion; and this requires judgment or discretion on the part of the person who swears. Secondly, as regards the point to be confirmed by oath, that it be neither false, nor unlawful, and this requires both truth, so that one employ an oath in order to confirm what is true, and justice, so that one confirm what is lawful. A rash oath lacks judgment, a false oath lacks truth, and a wicked or unlawful oath lacks justice.
Reply to Objection 1: Judgment does not signify here the execution of justice, but the judgment of discretion, as stated above. Nor is truth here to be taken for the part of justice, but for a condition of speech.
Reply to Objection 2: Devotion, faith and like conditions requisite for the right manner of swearing are implied by judgment: for the other two regard the things sworn to as stated above. We might also reply that justice regards the reason for swearing.
Reply to Objection 3: There is great danger in swearing, both on account of the greatness of God Who is called upon to bear witness, and on account of the frailty of the human tongue, the words of which are confirmed by oath. Hence these conditions are more requisite for an oath than for other human actions.
Whether an oath is an act of religion or latria?
Objection 1: It would seem that an oath is not an act of religion, or latria. Acts of religion are about holy and divine things. But oaths are employed in connection with human disputes, as the Apostle declares ( Heb. 6:16 ). Therefore swearing is not an act of religion or latria.
Objection 2: Further, it belongs to religion to give worship to God, as Tully says (De Invent. Rhet. ii, 53). But he who swears offers nothing to God, but calls God to be his witness. Therefore swearing is not an act of religion or latria.
Objection 3: Further, the end of religion or latria is to show reverence to God. But the end of an oath is not this, but rather the confirmation of some assertion. Therefore swearing is not an act of religion.
On the contrary, It is written ( Dt. 6:13 ): "Thou shalt fear the Lord thy God, and shalt serve Him only, and thou shalt swear by His name." Now he speaks there of the servitude of religion. Therefore swearing is an act of religion.
I answer that, As appears from what has been said above (A[1]), he that swears calls God to witness in confirmation of what he says. Now nothing is confirmed save by what is more certain and more powerful. Therefore in the very fact that a man swears by God, he acknowledges God to be more powerful, by reason of His unfailing truth and His universal knowledge; and thus in a way he shows reverence to God. For this reason the Apostle says ( Heb. 6:16 ) that "men swear by one greater than themselves," and Jerome commenting on Mat. 5:34, says that "he who swears either reveres or loves the person by whom he swears." The Philosopher, too, states (Metaph. i, 3) that "to swear is to give very great honor." Now to show reverence to God belongs to religion or latria. wherefore it is evident that an oath is an act of religion or latria.
Reply to Objection 1: Two things may be observed in an oath. The witness adduced, and this is Divine: and the thing witnessed to, or that which makes it necessary to call the witness, and this is human. Accordingly an oath belongs to religion by reason of the former, and not of the latter.
Reply to Objection 2: In the very fact that a man takes God as witness by way of an oath, he acknowledges Him to be greater: and this pertains to the reverence and honor of God, so that he offers something to God, namely, reverence and honor.
Reply to Objection 3: Whatsoever we do, we should do it in honor of God: wherefore there is no hindrance, if by intending to assure a man, we show reverence to God. For we ought so to perform our actions in God's honor that they may conduce to our neighbor's good, since God also works for His own glory and for our good.
Whether oaths are desirable and to be used frequently as something useful and good?