Front Page Titles (by Subject) QUESTION CX.: OF VICES OPPOSED TO TRUTHFULNESS, AND FIRST OF LYING. - Aquinas Ethicus: or, the Moral Teaching of St. Thomas, vol. 2 (Summa Theologica - Secunda Secundae Pt.2)
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QUESTION CX.: OF VICES OPPOSED TO TRUTHFULNESS, AND FIRST OF LYING. - St. Thomas Aquinas, Aquinas Ethicus: or, the Moral Teaching of St. Thomas, vol. 2 (Summa Theologica - Secunda Secundae Pt.2) 
Aquinas Ethicus: or, the Moral Teaching of St. Thomas. A Translation of the Principal Portions of the Second part of the Summa Theologica, with Notes by Joseph Rickaby, S.J. (London: Burns and Oates, 1892).
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OF VICES OPPOSED TO TRUTHFULNESS, AND FIRST OF LYING.
Article I.—Is lying always opposed to truthfulness?
R. A moral act has its species assigned to it according to its object and its end in view; for the end is the object of the will, and the will is the prime mover in moral acts. Again the power set in motion by the will has its own object, which is the proximate object of the voluntary act; and in the act of the will this object stands to the end in view as the material element to the formal.1 Now the virtue of truth, and consequently the opposite vices, both consist in a declaration made by means of certain signs, which declaration or assertion is an act of reason applying the sign to the thing signified: for every representation is a certain putting of things together, which is the proper act of reason. Hence though dumb animals give certain declarations or indications, yet they do not intend to indicate or declare anything; but they do some action by natural instinct, and on that instinct declaration ensues. In so far however as such declaration or assertion is a moral act, it must be voluntary, and dependent upon the intention of the will. The proper object of any declaration or assertion is truth or falsehood. And the intention of an inordinate will may be carried to two purposes: one is the utterance of a false assertion; the other is the proper effect of a false assertion, the deceiving of somebody. If then these three elements all combine, that the assertion made is false, that there is the will to make a false assertion, and lastly the intention to deceive: then there is falsehood materially, because what is said is false; and falsehood formally, on account of the will to utter what was false; and falsehood effectively, on account of the will to create a false impression. Nevertheless the essential character of lying is derived from formal falsehood, or from the fact of one having the will to assert what is false: a lie is speech against one’s mind. And therefore if any one asserts what is false, believing it to be true, it is a falsehood materially but not formally, because the falseness is beside the intention of the speaker. Hence it does not bear the perfect character of a lie: for what is beside the intention of the speaker is accidental, and therefore cannot constitute a specific difference. But if one utters a formal falsehood, with the intention of saying what is false, then though what is said be true, still such an act, so far as it is voluntary and moral, has falsehood of its own portion, and truth only accidentally: hence it attains to the species of lying. But as for one’s intending to create falsehood in the opinion and belief of another by deceiving him, that is not part of the specific nature of a lie, but goes to give the lie perfection: as in the physical world a thing attains to the species, if it has the form, even though the effect of the form be wanting.1 Thus it is clear that lying is directly and formally opposed to the virtue of truthfulness.
§ 1. Everything is rather judged by what is in it formally and ordinarily than by what is in it materially and incidentally. And therefore it is more opposed to the moral virtue of truthfulness for one to tell the truth, intending to tell a falsehood, than for one to tell a falsehood, intending to tell the truth.
§ 2. Speech holds the foremost place among signs. And therefore when it is said that a lie is a false intimation given by speech, under the name of speech is understood every sign. Hence he would not be guiltless of lying, who by nods and becks should endeavour to give any false intimation.
§ 3. The desire to deceive goes to make the lie perfect, but does not enter into its specific essence, as neither does any effect belong to the specific essence of its cause.
Article III.—Is every lie a sin?
R. What is evil of its kind can nowise be good and lawful: because for a thing to be good, all must be right that goes to make it up; for goodness supposes soundness all round, but any single defect makes an evil case. But a lie is evil of its kind; for it is an act falling on undue matter: for words being naturally signs of thoughts, it is a thing unnatural and undue for any one to signify in word what he has not in his mind.1
§ 4. A lie has the character of sinfulness, not only from the damage done to a neighbour, but also from its own inordinateness. Now it is not lawful to employ any unlawful inordinateness for the hindering of hurts and losses to others; as it is not lawful to steal in order to give alms. And therefore it is not lawful to tell a lie to deliver another from any danger whatever. It is lawful however to hide the truth prudently under some dissimulation, as Augustine says.2
§ 5. He who promises anything, if he has the intention of doing what he promises, does not lie; because he does not speak contrary to what he bears in his mind. But if afterwards he does not do what he has promised, then he seems to act unfaithfully by changing his mind. He may however be excused on two accounts. One is, if the thing promised is manifestly unlawful; in which case he sinned in promising, and does well in changing his mind. The other is, if the conditions of persons and things are changed. For as Seneca says, for a man to be bound to do as he has promised, it is requisite that all things remain unchanged: otherwise neither was he a liar in promising, because he promised what he had in his mind, due conditions being understood; nor is he unfaithful in not fulfilling what he promised, because the conditions do not remain the same.
§ 6. An act may be considered in one way in itself, in another way on the part of the agent. A jocose lie then has a character of deceit from the very kind of the act, though in the intention of the speaker it be not spoken to deceive, and from the manner of speaking actually do not deceive.1
Article IV.—Is every lie a mortal sin?
R. Mortal sin is properly that which is inconsistent with the charity whereby a soul is united to God. Now a lie may be contrary to charity in three ways: in itself, in the end intended, and accidentally. In itself it is contrary to charity as regards the falsity of the intimation given. If this is about divine things, it is contrary to the charity of God, whose truth is obscured or misrepresented by such a lie. Hence a lie of this nature is not only opposed to the virtue of charity, but also to the virtue of faith and religion: and accordingly this is a lie most grievous and mortal. But if the false intimation be about something that it appertains to man’s good to know of, for instance something bearing on the progress of knowledge and the formation of character, thereby bringing the prejudice of false opinion to a neighbour, it is contrary to charity in the department of love of our neighbour: hence it is a mortal sin. But if the false opinion generated by a lie turns on a point about which it does not matter whether one view or another be taken of it,—as if one should be deceived on some particular incidents that were no concern of his—then by such a lie no damage is done to our neighbour: hence it is not in itself a mortal sin. On the ground of the end intended, a lie is opposed to charity by being uttered either to the injury of God, which is always a mortal sin, as being opposed to religion; or to the hurt of our neighbour in his person, wealth, or good name; and this also is a mortal sin, since it is a mortal sin to hurt our neighbour, and the mere intention of mortal sin makes a mortal sin. But if the end intended be not contrary to charity, neither will the lie be a mortal sin in this respect; as appears in a jocose lie, that is intended to create some slight amusement, and in an officious lie, in which is intended even the advantage of our neighbour. Accidentally the lie may be contrary to charity by reason of the scandal it gives, or other damage ensuing from it; and so again it will be a mortal sin, for that the party is not deterred by fear of scandal from a barefaced, open lie.1
§ 5. Some say that in perfect men every lie is a mortal sin. But that is an irrational thing to say; for no circumstance aggravates infinitely unless by transferring the sin to another species. But the circumstance of person, who it is that offends—does not transfer the sin to another species, unless it be by reason of some adjunct, as of a vow that the person has made, which reason cannot be said to hold in the case of an officious or jocose lie. And therefore an officious or jocose lie is not a [grave] sin in perfect men, except it happen to become so by reason of the scandal given.
[1 ]As explained above, I-II. q. 18. art. 6.
[1 ]See Ethics and Natural Law, p. 225, n. 2 (Trl.)
[1 ]Ethics and Natural Law, pp. 228—230, nn. 4, 5, 6. (Trl.)
[2 ]A word to the wise: see Ethics and Natural Law, pp. 232—237.
[1 ]See however Ethics and Natural Law, p. 226. (Trl.)
[1 ]Once more it is to be remembered that the mortal sin against charity, so often insisted on by St. Thomas, supposes serious harm; where the harm is not serious, the sin is not mortal, on account of parvity of matter. Modern Catholic theologians agree, with what St. Thomas implicitly teaches here, that a lie pure and simple, as a sin against truth, is never a mortal sin, but becomes mortal by being complicated with some other sin, as against justice, charity, or religion. (Trl.)