Today’s Catechism sections discuss the taking of the Name of the Lord in vain, particularly false oaths and perjury. Supporting material comes from the letters of St. Augustine.

II. Taking the Name of the Lord in Vain

2150 The second commandment forbids false oaths. Taking an oath or swearing is to take God as witness to what one affirms. It is to invoke the divine truthfulness as a pledge of one's own truthfulness. An oath engages the Lord's name. "You shall fear the LORD your God; you shall serve him, and swear by his name."81

2151 Rejection of false oaths is a duty toward God. As Creator and Lord, God is the norm of all truth. Human speech is either in accord with or in opposition to God who is Truth itself. When it is truthful and legitimate, an oath highlights the relationship of human speech with God's truth. A false oath calls on God to be witness to a lie.

2152 A person commits perjury when he makes a promise under oath with no intention of keeping it, or when after promising on oath he does not keep it. Perjury is a grave lack of respect for the Lord of all speech. Pledging oneself by oath to commit an evil deed is contrary to the holiness of the divine name.

2153 In the Sermon on the Mount, Jesus explained the second commandment: "You have heard that it was said to the men of old, 'You shall not swear falsely, but shall perform to the Lord what you have sworn.' But I say to you, Do not swear at all.... Let what you say be simply 'Yes' or 'No'; anything more than this comes from the evil one."82 Jesus teaches that every oath involves a reference to God and that God's presence and his truth must be honored in all speech. Discretion in calling upon God is allied with a respectful awareness of his presence, which all our assertions either witness to or mock.

2154 Following St. Paul,83 The tradition of the Church has understood Jesus' words as not excluding oaths made for grave and right reasons (for example, in court). "An oath, that is the invocation of the divine name as a witness to truth, cannot be taken unless in truth, in judgment, and in justice."84

2155 The holiness of the divine name demands that we neither use it for trivial matters, nor take an oath which on the basis of the circumstances could be interpreted as approval of an authority unjustly requiring it. When an oath is required by illegitimate civil authorities, it may be refused. It must be refused when it is required for purposes contrary to the dignity of persons or to ecclesial communion.

IN BRIEF

2163 False oaths call on God to be witness to a lie. Perjury is a grave offence against the Lord who is always faithful to his promises.

2164 "Do not swear whether by the Creator, or any creature, except truthfully, of necessity, and with reverence" (St. Ignatius of Loyola, Spiritual Exercises, 38).

St. Augustine discusses oaths in “Letter 47” to “Publicola”.

2. One of your doubts is as to using the services of a man who has guaranteed his fidelity by swearing by his false gods. In this matter I beg you to consider whether, in the event of a man failing to keep his word after having pledged himself by such an oath, you would not regard him as guilty of a twofold sin. For if he kept the engagement which he had confirmed by this oath, he would be pronounced guilty in this only, that he swore by such deities; but no one would justly blame him for keeping his engagement. But in the case supposed, seeing that he both swore by those whom he should not worship, and did, notwithstanding his promise, what he should not have done, he was guilty of two sins: whence it is obvious that in using, not for an evil work, but for some good and lawful end, the service of a man whose fidelity is known to have been confirmed by an oath in the name of false gods, one participates, not in the sin of swearing by the false gods, but in the good faith with which he keeps his promise. The faith which I here speak of as kept is not that on account of which those who are baptized in Christ are called faithful: that is entirely different and far removed from the faith desiderated in regard to the arrangements and compacts of men. Nevertheless it is, beyond all doubt, worse to swear falsely by the true God than to swear truly by the false gods; for the greater the holiness of that by which we swear, the greater is the sin of perjury. It is therefore a different question whether he is not guilty who requires another to pledge himself by taking an oath in the name of his gods, seeing that he worships false gods. In answering this question, we may accept as decisive those examples which you yourself quoted of Laban and of Abimelech (if Abimelech did swear by his gods, as Laban swore by the god of Nahor). This is, as I have said, another question, and one which would perchance perplex me, were it not for those examples of Isaac and Jacob, to which, for anything I know, others might be added. It may be that some scruple might yet be suggested by the precept in the New Testament, Swear not at all; Matthew 5:34, 36 words which were in my opinion spoken, not because it is a sin to swear a true oath, but because it is a heinous sin to forswear oneself: from which crime our Lord would have us keep at a great distance, when He charged us not to swear at all. I know, however, that our opinion is different: wherefore it should not be discussed at present; let us rather treat of that about which you have thought of asking my advice. On the same ground on which you forbear from swearing yourself, you may, if such be your opinion, regard it as forbidden to exact an oath from another, although it is expressly said, Swear not; but I do not remember reading anywhere in Holy Scripture that we are not to take another's oath.

Footnotes

81 ⇒ Deut 6:13.
82 ⇒ Mt 5:33-34, ⇒ 37; Cf. ⇒ Jas 5:12.
83 Cf. ⇒ 2 Cor 1:23; ⇒ Gal 1:20.
84 ⇒ CIC, can. 1199 # 1.