Chapter 4 (153)
Distinction XXXIX | 163 is true does not seem to constitute perjury —SOLUTION. To this, we say that to speak in this way, namely against one's own mind and under the attestation of an oath, is perjury. And so to lie under oath is perjury.
Therefore perjury consists either in uttering a falsehood under oath with the intention of deceiving, or in uttering a falsehood under oath without the intention to deceive, or in telling a truth under oath with the intention of deceiving.
4. OBJECTION. Here an objection is made: If anyone who swears a falsehood commits perjury, then one who swears to give something to another by a certain term, which he then will not do, perjured himself at the swearing of his oath, because he swore a falsehood: for it did not turn out as he had sworn.—DETERMINATION. To this, it may be said that not everyone who swears what is false is a perjurer from the moment he swears, and this is the case with the person of whom we speak; it is from the moment that he changes his intention, or fails to meet the deadline, that such an oath becomes perjury.
Chapter 4 (153) 1. WHETHER IT IS AN EVIL TO SWEAR OATHS. But if it is asked whether it is evil to swear, we say that it is sometimes evil, sometimes not. For to swear voluntarily and without necessity, or to swear a falsehood, is a great sin. But to swear from necessity, namely either to assert one's innocence, or to confirm peace treaties, or to persuade one's listeners of something which is useful to them, is not evil because it is necessary.
2. AUGUSTINE, ON THE LORD'S SERMON ON THE MOUNT. Hence Augustine: "An oath is to be sworn in regard to necessary things, when men are slow in believing what is good for them. The swearing of oaths is not good; and yet it is not evil, if it is necessary,"' that is, it is not to be desired as if it were good, but neither is it to be avoided as if it were evil, when it is necessary.
3. AUGUSTINE, ON THE EPISTLE TO THE GALATIANS: "For the swearing of oaths is not against God's precept; the Lord's prohibition against oathswearing is to be understood in the sense that, insofar as it lies in him, one is not to swear: which many do, having an oath in their mouths as if it were something great and sweet. For the Apostle knew the Lord's precept, and yet he swore.' It follows that we are forbidden to swear out of a desire for and pleasure in swearing."
'Augustine, De sermone Domini in monte, bk 1 c17 n51.
PO rerome 19-11 Cor15, 31; 2 Cor, 11, 3.12 Gal: 1,30; Phil. 1, 8:
*Augustine, Epistolae ad Galatas (1, 20) expositio, n9.