St. Augustine, Against Lying (Contra Mendacio): "To this end, therefore, that their lie may be blotted out, or shunned, and God's truth increased. How then by a lie shall I rightly be able to prosecute lies? Or is it by robbery that robberies and by sacrilege that sacrileges, and by adultery that adulteries, are to be prosecuted? "But if the truth of God shall abound by my lie," are we too to say, "Let us do evil that good may come?" A thing which you see how the Apostle detests."
St. Augustine, On Lying (De Mendacio), circa 395: "...Truth is that which sets free from all error, and Falsehood that which entangles in all error, one never errs more safely, methinks, than when one errs by too much loving the truth, and too much rejecting of falsehood. For they who find great fault say it is too much, whereas perhaps Truth would say after all, it is not yet enough.
"Setting aside, therefore, jokes, which have never been accounted lies, seeing they bear with them in the tone of voice, and in the very mood of the joker a most evident indication that he means no deceit, although the thing he utters be not true: touching which kind of discourse, whether it be meet to be used by perfect minds, is another question which we have not at this time taken in hand to clear; but setting jokes apart, the first point to be attended to, is, that a person should not be thought to lie, who lies not."
It is well to note here that St. Augustine does not consider such telling of jokes, or as St. Thomas Aquinas calls them "jocose lies" to be actual lies, or to be sinful, even if he finds them unbefitting of perfect minds. However St. Thomas disagrees:
St. Thomas, Summa Theologica, Secuna Secundae Partis, Q. 110: "It is written (Sirach 7:14): "Be not willing to make any manner of lie
"An action that is naturally evil in respect of its genus can by no means be good and lawful, since in order for an action to be good it must be right in every respect: because good results from a complete cause, while evil results from any single defect, as Dionysius asserts (Div. Nom. iv). Now a lie is evil in respect of its genus, since it is an action bearing on undue matter. For as words are naturally signs of intellectual acts, it is unnatural and undue for anyone to signify by words something that is not in his mind.
"But if the end intended be not contrary to charity, neither will the lie, considered under this aspect, be a mortal sin, as in the case of a jocose lie, where some little pleasure is intended, or in an officious lie, where the good also of one's neighbor is intended."
St. Thomas nevertheless considered such jocose lies to be venial sins. And both he and Augustine seem to agree that perfect minds (that is, minds consecrated solely to the love and service of God) have no place in uttering such jokes or jocose lies.
St. Augustine continues:
St. Augustine, On Lying (De Mendacio), circa 395: "For first they (who are against all lying) teach, that a lie is iniquity, by many proofs of holy writ, especially by that which is written, "You, Lord, hatest all workers of iniquity, you shall destroy them that speak leasing." For either as the Scripture is wont, in the following clause it expounds the former; so that, as iniquity is a term of a wider meaning, leasing is named as the particular sort of iniquity intended: or if they think there is any difference between the two, leasing is by so much worse than iniquity as "you will destroy" is heavier than "you hate." For it may be that God hates a person to that degree more mildly, as not to destroy him, but whom He destroys He hates the more exceedingly, by how much He punishes more severely. Now He hates all who work iniquity: but all who speak leasing He also destroys.
"As concerning purity of body; here indeed a very honorable regard seems to come in the way, and to demand a lie in its behalf; to wit, that if the assault of the ravisher may be escaped by means of a lie, it is indubitably right to tell it: but to this it may easily be answered, that there is no purity of body except as it depends on integrity of mind; this being broken, the other must needs fall, even though it seem intact; and for this reason it is not to be reckoned among temporal things, as a thing that might be taken away from people against their will.
"Wherefore, either we must not believe good men, or we must believe those whom we think obliged sometimes to tell a lie, or we must not believe that good men sometimes tell lies: of these three the first is pernicious, the second foolish; it remains therefore that good men should never tell lies."