Nicene and Post-Nicene Fathers, Vol. III:
Moral Treatises of St. Augustin: Section 4

4. But it may be a very nice question whether in the absence of all will to deceive, lying is altogether absent. Thus, put the case that a person shall speak a false thing, which he esteems to be false, on the ground that he thinks he is not believed, to the intent, that in that way falsifying his faith he may deter the person to whom he speaks, which person he perceives does not choose to believe him. For here is a person who tells a lie with studied purpose of not deceiving, if to tell a lie is to utter any thing otherwise than you know or think it to be. But if it be no lie, unless when something is uttered with wish to deceive, that person lies not, who says a false thing, knowing or thinking it to be false, but says it on purpose that the person to whom he speaks by not believing him may not be deceived, because the speaker either knows or thinks the other will not believe him. Whence if it appear to be possible that a person should say a false thing on purpose that he to whom it is said may not be deceived, on the other hand there is this opposite case, the case of a person saying the truth on purpose that he may deceive. For if a man determines to say a true thing because he perceives he is not believed, that man speaks truth on purpose that he may deceive: for he knows or thinks that what is said may be accounted false, just because it is spoken by him. Wherefore in saying a true thing on purpose that it may be thought false, he says a true thing on purpose to deceive. So that it may be inquired, which rather lies: he who says a false thing that he p. 459 may not deceive, or he who says a true thing that he may deceive? the one knowing or thinking that he says a false thing, and the other knowing or thinking that he says a true thing? For we have already said that the person who does not know the thing to be false which he utters, does not lie if he thinks it to be true; and that that person rather lies who utters even a true thing when he thinks it false: because it is by the sense of their mind that they are to be judged. Concerning these persons therefore, whom we have set forth, there is no small question. The one, who knows or thinks he says a false thing, and says it on purpose that he may not deceive: as, if he knows a certain road to be beset by robbers, and fearing lest some person for whose safety he is anxious should go by that road, which person he knows does not trust him, should tell him that that road has no robbers, on purpose that he may not go by it, as he will think there are robbers there precisely because the other has told him there are none, and he is resolved not to believe him, accounting him a liar. The other, who knowing or thinking that to be true which he says, says it on purpose that he may deceive: for instance, if he tells a person who does not believe him, that there are robbers in that road where he really knows them to be, that he to whom he tells it may the rather go by that road and so fall among robbers, because he thinks that to be false, which the other told him. Which then of these lies? the one who has chosen to say a false thing that he may not deceive? or the other who has chosen to say a true thing that he may deceive? that one, who in saying a false thing aimed that he to whom he spake should follow the truth? or this one, who in saying a true thing aimed that he to whom he spake should follow a falsehood? Or haply have both lied? the one, because he wished to say a false thing: the other, because he wished to deceive? Or rather, has neither lied? not the one, because he had the will not to deceive: not the other, because he had the will to speak the truth? For the question is not now which of them sinned, but which of them lied: as indeed it is presently seen that the latter sinned, because by speaking a truth he brought it about that a person should fall among robbers, and that the former has not sinned, or even has done good, because by speaking a false thing he has been the means of a person’s avoiding destruction. But then these instances may be turned the other way, so that the one should be supposed to wish some more grievous suffering to the person whom he wishes not to be deceived; for there are many cases of persons who through knowing certain things to be true, have brought destruction upon themselves, if the things were such as ought to have continued unknown to them: and the other may be supposed to wish some convenience to result to the person whom he wishes to be deceived; for there have been instances of persons who would have destroyed themselves had they known some evil that had really befallen those who were dear to them, and through deeming it false have spared themselves: and so to be deceived has been a benefit to them, as to others it has been a hurt to know the truth. The question therefore is not with what purpose of doing a kindness or a hurt, either the one said a false thing that he might not deceive, or the other a true thing that he might deceive: but, setting apart the convenience or inconvenience of the persons spoken to, in so far as relates to the very truth and falsehood, the question is, whether both of them or neither has lied. For if a lie is an utterance with will of uttering a false thing, that man has rather lied who willed to say a false thing, and said what he willed, albeit he said it of set purpose not to deceive. But if a lie is any utterance whatever with will to deceive; then not the former has lied, but the latter, who even in speaking truth willed to deceive. And if a lie is an utterance with will of any falsity, both have lied; because both the former willed his utterance to be false, and the latter willed a false thing to be believed concerning his utterance which was true. Further, if a lie is an utterance of a person wishing to utter a false thing that he may deceive, neither has lied; because both the former in saying a false thing had the will to make a true thing believed, and the latter to say a true thing in order that he might make a false thing believed. We shall be clear then of all rashness and all lying, if, what we know to be true or right to be believed, we utter when need is, and wish to make that thing believed which we utter. If, however, either thinking that to be true which is false, or accounting as known that which is to us unknown, or believing what we ought not to believe, or uttering it when need is not, we yet have no other aim than to make that believed which we utter; we do not stand clear indeed of the error of temerity, but we do stand clear of all lying. For there is no need to be afraid of any of those definitions, when the mind has a good conscience, that it utters that which to be true it either knows, or opines, or believes, and that it has no wish p. 460 to make any thing believed but that which it utters.