Summa Th. II-II EN Qu.108 a.2
Objection: 1. It seems that vengeance is not a special and distinct virtue. For just as the good are rewarded for their good deeds, so are the wicked punished for their evil deeds. Now the rewarding of the good does not belong to a special virtue, but is an act of commutative justice. Therefore in the same way vengeance should not be accounted a special virtue.
2. Further, there is no need to appoint a special virtue for an act to which a man is sufficiently disposed by the other virtues. Now man is sufficiently disposed by the virtues of fortitude or zeal to avenge evil. Therefore vengeance should not be reckoned a special virtue.
3. Further, there is a special vice opposed to every special virtue. But seemingly no special vice is opposed to vengeance. Therefore it is not a special virtue.
On the contrary Tully (De Invent. Rhet. ii) reckons it a part of justice.
I answer that As the Philosopher states (Ethic. ii, 1), aptitude to virtue is in us by nature, but the complement of virtue is in us through habituation or some other cause. Hence it is evident that virtues perfect us so that we follow in due manner our natural inclinations, which belong to the natural right. Wherefore to every definite natural inclination there corresponds a special virtue. Now there is a special inclination of nature to remove harm, for which reason animals have the irascible power distinct from the concupiscible. Man resists harm by defending himself against wrongs, lest they be inflicted on him, or he avenges those which have already been inflicted on him, with the intention, not of harming, but of removing the harm done. And this belongs to vengeance, for Tully says (De Invent. Rhet. ii) that by "vengeance we resist force, or wrong, and in general whatever is obscure" [*'Obscurum' Cicero wrote 'obfuturum' but the sense is the same as St. Thomas gives in the parenthesis] "(i.e. derogatory), either by self-defense or by avenging it." Therefore vengeance is a special virtue.
Reply to Objection: 1. Just as repayment of a legal debt belongs to commutative justice, and as repayment of a moral debt, arising from the bestowal of a particular favor, belongs to the virtue of gratitude, so too the punishment of sins, so far as it is the concern of public justice, is an act of commutative justice; while so far as it is concerned in defending the rights of the individual by whom a wrong is resisted, it belongs to the virtue of revenge.
2. Fortitude disposes to vengeance by removing an obstacle thereto, namely, fear of an imminent danger. Zeal, as denoting the fervor of love, signifies the primary root of vengeance, in so far as a man avenges the wrong done to God and his neighbor, because charity makes him regard them as his own. Now every act of virtue proceeds from charity as its root, since, according to Gregory (Hom. xxvii in ), "there are no green leaves on the bough of good works, unless charity be the root."
3. Two vices are opposed to vengeance: one by way of excess, namely, the sin of cruelty or brutality, which exceeds the measure in punishing: while the other is a vice by way of deficiency and consists in being remiss in punishing, wherefore it is written (Pr 13,24): "He that spareth the rod hateth his son." But the virtue of vengeance consists in observing the due measure of vengeance with regard to all the circumstances.
Objection: 1. It seems that vengeance should not be wrought by means of punishments customary among men. For to put a man to death is to uproot him. But our Lord forbade (Mt 13,29) the uprooting of the cockle, whereby the children of the wicked one are signified. Therefore sinners should not be put to death.
2. Further, all who sin mortally seem to be deserving of the same punishment. Therefore if some who sin mortally are punished with death, it seems that all such persons should be punished with death: and this is evidently false.
3. Further, to punish a man publicly for his sin seems to publish his sin: and this would seem to have a harmful effect on the multitude, since the example of sin is taken by them as an occasion for sin. Therefore it seems that the punishment of death should not be inflicted for a sin.
On the contrary These punishments are fixed by the divine law as appears from what we have said above (FS, Question , Article ).
I answer that Vengeance is lawful and virtuous so far as it tends to the prevention of evil. Now some who are not influenced by motive of virtue are prevented from committing sin, through fear of losing those things which they love more than those they obtain by sinning, else fear would be no restraint to sin. Consequently vengeance for sin should be taken by depriving a man of what he loves most. Now the things which man loves most are life, bodily safety, his own freedom, and external goods such as riches, his country and his good name. Wherefore, according to Augustine's reckoning (De Civ. Dei xxi), "Tully writes that the laws recognize eight kinds of punishment": namely, "death," whereby man is deprived of life; "stripes," "retaliation," or the loss of eye for eye, whereby man forfeits his bodily safety; "slavery," and "imprisonment," whereby he is deprived of freedom; "exile" whereby he is banished from his country; "fines," whereby he is mulcted in his riches; "ignominy," whereby he loses his good name.
Reply to Objection: 1. Our Lord forbids the uprooting of the cockle, when there is fear lest the wheat be uprooted together with it. But sometimes the wicked can be uprooted by death, not only without danger, but even with great profit, to the good. Wherefore in such a case the punishment of death may be inflicted on sinners.
2. All who sin mortally are deserving of eternal death, as regards future retribution, which is in accordance with the truth of the divine judgment. But the punishments of this life are more of a medicinal character; wherefore the punishment of death is inflicted on those sins alone which conduce to the grave undoing of others.
3. The very fact that the punishment, whether of death or of any kind that is fearsome to man, is made known at the same time as the sin, makes man's will avers to sin: because the fear of punishment is greater than the enticement of the example of sin.
Objection: 1. It seems that vengeance should be taken on those who have sinned involuntarily. For the will of one man does not follow from the will of another. Yet one man is punished for another, according to Ex 20,5, "I am . . . God . . . jealous, visiting the iniquity of the fathers upon the children, unto the third and fourth generation." Thus for the sin of Cham, his son Chanaan was curse (Gn 9,25) and for the sin of Giezi, his descendants were struck with leprosy (2R 5). Again the blood of Christ lays the descendants of the Jews under the ban of punishment, for they said (Mt 27,25): "His blood be upon us and upon our children." Moreover we read (Jos 7) that the people of Israel were delivered into the hands of their enemies for the sin of Achan, and that the same people were overthrown by the Philistines on account of the sin of the sons of Heli (1R 4). Therefore a person is to be punished without having deserved it voluntarily.
2. Further, nothing is voluntary except what is in a man's power. But sometimes a man is punished for what is not in his power; thus a man is removed from the administration of the Church on account of being infected with leprosy; and a Church ceases to be an episcopal see on account of the depravity or evil of the people. Therefore vengeance is taken not only for voluntary sins.
3. Further, ignorance makes an act involuntary. Now vengeance is sometimes taken on the ignorant. Thus the children of the people of Sodom, though they were in invincible ignorance, perished with their parents (Gn 19). Again, for the sin of Dathan and Abiron their children were swallowed up together with them (Nb 16). Moreover, dumb animals, which are devoid of reason, were commanded to be slain on account of the sin of the Amalekites (1R 15). Therefore vengeance is sometimes taken on those who have deserved it involuntarily.
4. Further, compulsion is most opposed to voluntariness. But a man does not escape the debt of punishment through being compelled by fear to commit a sin. Therefore vengeance is sometimes taken on those who have deserved it involuntarily.
5. Further Ambrose says on Lc 5 that "the ship in which Judas was, was in distress"; wherefore "Peter, who was calm in the security of his own merits, was in distress about those of others." But Peter did not will the sin of Judas. Therefore a person is sometimes punished without having voluntarily deserved it.
On the contrary Punishment is due to sin. But every sin is voluntary according to Augustine (De Lib. Arb. iii; Retract. i). Therefore vengeance should be taken only on those who have deserved it voluntarily.
I answer that Punishment may be considered in two ways. First, under the aspect of punishment, and in this way punishment is not due save for sin, because by means of punishment the equality of justice is restored, in so far as he who by sinning has exceeded in following his own will suffers something that is contrary to this will. Wherefore, since every sin is voluntary, not excluding original sin, as stated above (FS, Question , Article ), it follows that no one is punished in this way, except for something done voluntarily. Secondly, punishment may be considered as a medicine, not only healing the past sin, but also preserving from future sin, or conducing to some good, and in this way a person is sometimes punished without any fault of his own, yet not without cause.It must, however, be observed that a medicine never removes a greater good in order to promote a lesser; thus the medicine of the body never blinds the eye, in order to repair the heel: yet sometimes it is harmful in lesser things that it may be helpful in things of greater consequence. And since spiritual goods are of the greatest consequence, while temporal goods are least important, sometimes a person is punished in his temporal goods without any fault of his own. Such are many of the punishments inflicted by God in this present life for our humiliation or probation. But no one is punished in spiritual goods without any fault on his part, neither in this nor in the future life, because in the latter punishment is not medicinal, but a result of spiritual condemnation.
Reply to Objection: 1. A man is never condemned to a spiritual punishment for another man's sin, because spiritual punishment affects the soul, in respect of which each man is master of himself. But sometimes a man is condemned to punishment in temporal matters for the sin of another, and this for three reasons. First, because one man may be the temporal goods of another, and so he may be punished in punishment of the latter: thus children, as to the body, are a belonging of their father, and slaves are a possession of their master. Secondly, when one person's sin is transmitted to another, either by "imitation," as children copy the sins of their parents, and slaves the sins of their masters, so as to sin with greater daring; or by way of "merit," as the sinful subjects merit a sinful superior, according to Jb 34,30, "Who maketh a man that is a hypocrite to reign for the sins of the people?" Hence the people of Israel were punished for David's sin in numbering the people (2S 24). This may also happen through some kind of "consent" or "connivance": thus sometimes even the good are punished in temporal matters together with the wicked, for not having condemned their sins, as Augustine says (De Civ. Dei i, 9). Thirdly, in order to mark the unity of human fellowship, whereby one man is bound to be solicitous for another, lest he sin; and in order to inculcate horror of sin, seeing that the punishment of one affects all, as though all were one body, as Augustine says in speaking of the sin of Achan (Questions. sup. Josue viii). The saying of the Lord, "Visiting the iniquity of the fathers upon the children unto the third and fourth generation," seems to belong to mercy rather than to severity, since He does not take vengeance forthwith, but waits for some future time, in order that the descendants at least may mend their ways; yet should the wickedness of the descendants increase, it becomes almost necessary to take vengeance on them.
2. As Augustine states (Questions. sup. Josue viii), human judgment should conform to the divine judgment, when this is manifest, and God condemns men spiritually for their own sins. But human judgment cannot be conformed to God's hidden judgments, whereby He punishes certain persons in temporal matters without any fault of theirs, since man is unable to grasp the reasons of these judgments so as to know what is expedient for each individual. Wherefore according to human judgment a man should never be condemned without fault of his own to an inflictive punishment, such as death, mutilation or flogging. But a man may be condemned, even according to human judgment, to a punishment of forfeiture, even without any fault on his part, but not without cause: and this in three ways.First, through a person becoming, without any fault of his, disqualified for having or acquiring a certain good: thus for being infected with leprosy a man is removed from the administration of the Church: and for bigamy, or through pronouncing a death sentence a man is hindered from receiving sacred orders.Secondly, because the particular good that he forfeits is not his own but common property: thus that an episcopal see be attached to a certain church belongs to the good of the whole city, and not only to the good of the clerics.Thirdly, because the good of one person may depend on the good of another: thus in the crime of high treason a son loses his inheritance through the sin of his parent.
3. By the judgment of God children are punished in temporal matters together with their parents, both because they are a possession of their parents, so that their parents are punished also in their person, and because this is for their good lest, should they be spared, they might imitate the sins of their parents, and thus deserve to be punished still more severely. Vengeance is wrought on dumb animals and any other irrational creatures, because in this way their owners are punished; and also in horror of sin.
4. An act done through compulsion of fear is not involuntary simply, but has an admixture of voluntariness, as stated above (FS, Question , Articles ,6).
5. The other apostles were distressed about the sin of Judas, in the same way as the multitude is punished for the sin of one, in commendation of unity, as state above (Reply Objection ,2).
We must now consider truth and the vices opposed thereto. Concerning truth there are four points of inquiry:
(1) Whether truth is a virtue?
(2) Whether it is a special virtue?
(3) Whether it is a part of justice?
(4) Whether it inclines to that which is less?
Objection: 1. It seems that truth is not a virtue. For the first of virtues is faith, whose object is truth. Since then the object precedes the habit and the act, it seems that truth is not a virtue, but something prior to virtue.
2. Further, according to the Philosopher (Ethic. iv, 7), it belongs to truth that a man should state things concerning himself to be neither more nor less than they are. But this is not always praiseworthy---neither in good things, since according to Pr 27,2, "Let another praise thee, and not thy own mouth"---nor even in evil things, because it is written in condemnation of certain people (Is 3,9): "They have proclaimed abroad their sin as Sodom, and they have not hid it." Therefore truth is not a virtue.
3. Further, every virtue is either theological, or intellectual, or moral. Now truth is not a theological virtue, because its object is not God but temporal things. For Tully says (De Invent. Rhet. ii) that by "truth we faithfully represent things as they are were, or will be." Likewise it is not one of the intellectual virtues, but their end. Nor again is it a moral virtue, since it is not a mean between excess and deficiency, for the more one tells the truth, the better it is. Therefore truth is not a virtue.
On the contrary The Philosopher both in the Second and in the Fourth Book of Ethics places truth among the other virtues.
I answer that Truth can be taken in two ways. First, for that by reason of which a thing is said to be true, and thus truth is not a virtue, but the object or end of a virtue: because, taken in this way, truth is not a habit, which is the genus containing virtue, but a certain equality between the understanding or sign and the thing understood or signified, or again between a thing and its rule, as stated in the FP, Question , Article ; FP, Question , Article . Secondly, truth may stand for that by which a person says what is true, in which sense one is said to be truthful. This truth or truthfulness must needs be a virtue, because to say what is true is a good act: and virtue is "that which makes its possessor good, and renders his action good."
Reply to Objection: 1. This argument takes truth in the first sense.
2. To state that which concerns oneself, in so far as it is a statement of what is true, is good generically. Yet this does not suffice for it to be an act of virtue, since it is requisite for that purpose that it should also be clothed with the due circumstances, and if these be not observed, the act will be sinful. Accordingly it is sinful to praise oneself without due cause even for that which is true: and it is also sinful to publish one's sin, by praising oneself on that account, or in any way proclaiming it uselessly.
3. A person who says what is true, utters certain signs which are in conformity with things; and such signs are either words, or external actions, or any external thing. Now such kinds of things are the subject-matter of the moral virtues alone, for the latter are concerned with the use of the external members, in so far as this use is put into effect at the command of the will. Wherefore truth is neither a theological, nor an intellectual, but a moral virtue. And it is a mean between excess and deficiency in two ways. First, on the part of the object, secondly, on the part of the act. On the part of the object, because the true essentially denotes a kind of equality, and equal is a mean between more and less. Hence for the very reason that a man says what is true about himself, he observes the mean between one that says more than the truth about himself, and one that says less than the truth. On the part of the act, to observe the mean is to tell the truth, when one ought, and as one ought. Excess consists in making known one's own affairs out of season, and deficiency in hiding them when one ought to make them known.
Objection: 1. It seems that truth is not a special virtue. For the true and the good are convertible. Now goodness is not a special virtue, in fact every virtue is goodness, because "it makes its possessor good." Therefore truth is not a special virtue.
2. Further, to make known what belongs to oneself is an act of truth as we understand it here. But this belongs to every virtue, since every virtuous habit is made known by its own act. Therefore truth is not a special virtue.
3. Further, the truth of life is the truth whereby one lives aright, and of which it is written (Is 38,3): "I beseech Thee . . . remember how I have walked before Thee in truth, and with a perfect heart." Now one lives aright by any virtue, as follows from the definition of virtue given above (FS, Question , Article ). Therefore truth is not a special virtue.
4. Further, truth seems to be the same as simplicity, since hypocrisy is opposed to both. But simplicity is not a special virtue, since it rectifies the intention, and that is required in every virtue. Therefore neither is truth a special virtue.
On the contrary It is numbered together with other virtues (Ethic. ii, 7).
I answer that The nature of human virtue consists in making a man's deed good. Consequently whenever we find a special aspect of goodness in human acts, it is necessary that man be disposed thereto by a special virtue. And since according to Augustine (De Nat. Boni iii) good consists in order, it follows that a special aspect of good will be found where there is a special order. Now there is a special order whereby our externals, whether words or deeds, are duly ordered in relation to some thing, as sign to thing signified: and thereto man is perfected by the virtue of truth. Wherefore it is evident that truth is a special virtue.
Reply to Objection: 1. The true and the good are convertible as to subject, since every true thing is good, and every good thing is true. But considered logically, they exceed one another, even as the intellect and will exceed one another. For the intellect understands the will and many things besides, and the will desires things pertaining to the intellect, and many others. Wherefore the "true" considered in its proper aspect as a perfection of the intellect is a particular good, since it is something appetible: and in like manner the "good" considered in its proper aspect as the end of the appetite is something true, since it is something intelligible. Therefore since virtue includes the aspect of goodness, it is possible for truth to be a special virtue, just as the "true" is a special good; yet it is not possible for goodness to be a special virtue, since rather, considered logically, it is the genus of virtue.
2. The habits of virtue and vice take their species from what is directly intended, and not from that which is accidental and beside the intention. Now that a man states that which concerns himself, belongs to the virtue of truth, as something directly intended: although it may belong to other virtues consequently and beside his principal intention. For the brave man intends to act bravely: and that he shows his fortitude by acting bravely is a consequence beside his principal intention.
3. The truth of life is the truth whereby a thing is true, not whereby a person says what is true. Life like anything else is said to be true, from the fact that it attains its rule and measure, namely, the divine law; since rectitude of life depends on conformity to that law. This truth or rectitude is common to every virtue.
4. Simplicity is so called from its opposition to duplicity, whereby, to wit, a man shows one thing outwardly while having another in his heart: so that simplicity pertains to this virtue. And it rectifies the intention, not indeed directly (since this belongs to every virtue), but by excluding duplicity, whereby a man pretends one thing and intends another.
Objection: 1. It seems that truth is not a part of justice. For it seems proper to justice to give another man his due. But, by telling the truth, one does not seem to give another man his due, as is the case in all the foregoing parts of justice. Therefore truth is not a part of justice.
2. Further, truth pertains to the intellect: whereas justice is in the will, as stated above (Question , Article ). Therefore truth is not a part of justice.
3. Further, according to Jerome truth is threefold, namely, "truth of life," "truth of justice," and "truth of doctrine." But none of these is a part of justice. For truth of life comprises all virtues, as stated above (Article , ad 3): truth of justice is the same as justice, so that it is not one of its parts; and truth of doctrine belongs rather to the intellectual virtues. Therefore truth is nowise a part of justice.
On the contrary Tully (De Invent. Rhet. ii) reckons truth among the parts of justice.
I answer that As stated above (Question ), a virtue is annexed to justice, as secondary to a principal virtue, through having something in common with justice, while falling short from the perfect virtue thereof. Now the virtue of truth has two things in common with justice. In the first place it is directed to another, since the manifestation, which we have stated to be an act of truth, is directed to another, inasmuch as one person manifests to another the things that concern himself. In the second place, justice sets up a certain equality between things, and this the virtue of truth does also, for it equals signs to the things which concern man himself. Nevertheless it falls short of the proper aspect of justice, as to the notion of debt: for this virtue does not regard legal debt, which justice considers, but rather the moral debt, in so far as, out of equity, one man owes another a manifestation of the truth. Therefore truth is a part of justice, being annexed thereto as a secondary virtue to its principal.
Reply to Objection: 1. Since man is a social animal, one man naturally owes another whatever is necessary for the preservation of human society. Now it would be impossible for men to live together, unless they believed one another, as declaring the truth one to another. Hence the virtue of truth does, in a manner, regard something as being due.
2. Truth, as known, belongs to the intellect. But man, by his own will, whereby he uses both habits and members, utters external signs in order to manifest the truth, and in this way the manifestation of the truth is an act of the will.
3. The truth of which we are speaking now differs from the truth of life, as stated in the preceding Article , ad 3.We speak of the truth of justice in two ways. In one way we refer to the fact that justice itself is a certain rectitude regulated according to the rule of the divine law; and in this way the truth of justice differs from the truth of life, because by the truth of life a man lives aright in himself, whereas by the truth of justice a man observes the rectitude of the law in those judgments which refer to another man: and in this sense the truth of justice has nothing to do with the truth of which we speak now, as neither has the truth of life. In another way the truth of justice may be understood as referring to the fact that, out of justice, a man manifests the truth, as for instance when a man confesses the truth, or gives true evidence in a court of justice. This truth is a particular act of justice, and does not pertain directly to this truth of which we are now speaking, because, to wit, in this manifestation of the truth a man's chief intention is to give another man his due. Hence the Philosopher says (Ethic. iv, 7) in describing this virtue: "We are not speaking of one who is truthful in his agreements, nor does this apply to matters in which justice or injustice is questioned."
The truth of doctrine consists in a certain manifestation of truths relating to science wherefore neither does this truth directly pertain to this virtue, but only that truth whereby a man, both in life and in speech, shows himself to be such as he is, and the things that concern him, not other, and neither greater nor less, than they are. Nevertheless since truths of science, as known by us, are something concerning us, and pertain to this virtue, in this sense the truth of doctrine may pertain to this virtue, as well as any other kind of truth whereby a man manifests, by word or deed, what he knows.
Objection: 1. It seems that the virtue of truth does not incline to that which is less. For as one incurs falsehood by saying more, so does one by saying less: thus it is no more false that four are five, than that four are three. But "every falsehood is in itself evil, and to be avoided," as the Philosopher declares (Ethic. iv, 7). Therefore the virtue of truth does not incline to that which is less rather than to that which is greater.
2. Further, that a virtue inclines to the one extreme rather than to the other, is owing to the fact that the virtue's mean is nearer to the one extreme than to the other: thus fortitude is nearer to daring than to timidity. But the mean of truth is not nearer to one extreme than to the other; because truth, since it is a kind of equality, holds to the exact mean. Therefore truth does not more incline to that which is less.
3. Further, to forsake the truth for that which is less seems to amount to a denial of the truth, since this is to subtract therefrom; and to forsake the truth for that which is greater seems to amount to an addition thereto. Now to deny the truth is more repugnant to truth than to add something to it, because truth is incompatible with the denial of truth, whereas it is compatible with addition. Therefore it seems that truth should incline to that which is greater rather than to that which is less.
On the contrary The Philosopher says (Ethic. iv, 7) that "by this virtue a man declines rather from the truth towards that which is less."
I answer that There are two ways of declining from the truth to that which is less. First, by affirming, as when a man does not show the whole good that is in him, for instance science, holiness and so forth. This is done without prejudice to truth, since the lesser is contained in the greater: and in this way this virtue inclines to what is less. For, as the Philosopher says (Ethic. iv, 7), "this seems to be more prudent because exaggerations give annoyance." For those who represent themselves as being greater than they are, are a source of annoyance to others, since they seem to wish to surpass others: whereas those who make less account of themselves are a source of pleasure, since they seem to defer to others by their moderation. Hence the Apostle says (2Co 12,6): "Though I should have a mind to glory, I shall not be foolish: for I will say the truth. But I forbear, lest any man should think of me above that which he seeth in me or anything he heareth from me."Secondly, one may incline to what is less by denying, so as to say that what is in us is not. In this way it does not belong to this virtue to incline to what is less, because this would imply falsehood. And yet this would be less repugnant to the truth, not indeed as regards the proper aspect of truth, but as regards the aspect of prudence, which should be safeguarded in all the virtues. For since it is fraught with greater danger and is more annoying to others, it is more repugnant to prudence to think or boast that one has what one has not, than to think or say that one has not what one has.
Reply to Objection: 1. This suffices for the Replies to the Objections.
We must now consider the vices opposed to truth, and (1) lying: (2) dissimulation or hypocrisy: (3) boasting and the opposite vice. Concerning lying there are four points of inquiry:
(1) Whether lying, as containing falsehood, is always opposed to truth?
(2) Of the species of lying;
(3) Whether lying is always a sin?
(4) Whether it is always a mortal sin?
Objection: 1. It seems that lying is not always opposed to truth. For opposites are incompatible with one another. But lying is compatible with truth, since that speaks the truth, thinking it to be false, lies, according to Augustine (Lib. De Mendac. iii). Therefore lying is not opposed to truth.
2. Further, the virtue of truth applies not only to words but also to deeds, since according to the Philosopher (Ethic. iv, 7) by this virtue one tells the truth both in one's speech and in one's life. But lying applies only to words, for Augustine says (Contra Mend. xii) that "a lie is a false signification by words." Accordingly, it seems that lying is not directly opposed to the virtue of truth.
3. Further, Augustine says (Lib. De Mendac. iii) that the "liar's sin is the desire to deceive." But this is not opposed to truth, but rather to benevolence or justice. Therefore lying is not opposed to truth.
On the contrary Augustine says (Contra Mend. x): "Let no one doubt that it is a lie to tell a falsehood in order to deceive. Wherefore a false statement uttered with intent to deceive is a manifest lie." But this is opposed to truth. Therefore lying is opposed to truth.
I answer that A moral act takes its species from two things, its object, and its end: for the end is the object of the will, which is the first mover in moral acts. And the power moved by the will has its own object, which is the proximate object of the voluntary act, and stands in relation to the will's act towards the end, as material to formal, as stated above (FS, Question , Articles ,7).Now it has been said above (Question , Article , ad 3) that the virtue of truth---and consequently the opposite vices---regards a manifestation made by certain signs: and this manifestation or statement is an act of reason comparing sign with the thing signified; because every representation consists in comparison, which is the proper act of the reason. Wherefore though dumb animals manifest something, yet they do not intend to manifest anything: but they do something by natural instinct, and a manifestation is the result. But when this manifestation or statement is a moral act, it must needs be voluntary, and dependent on the intention of the will. Now the proper object of a manifestation or statement is the true or the false. And the intention of a bad will may bear on two things: one of which is that a falsehood may be told; while the other is the proper effect of a false statement, namely, that someone may be deceived.Accordingly if these three things concur, namely, falsehood of what is said, the will to tell a falsehood, and finally the intention to deceive, then there is falsehood---materially, since what is said is false, formally, on account of the will to tell an untruth, and effectively, on account of the will to impart a falsehood.However, the essential notion of a lie is taken from formal falsehood, from the fact namely, that a person intends to say what is false; wherefore also the word "mendacium" [lie] is derived from its being in opposition to the "mind." Consequently if one says what is false, thinking it to be true, it is false materially, but not formally, because the falseness is beside the intention of the speaker so that it is not a perfect lie, since what is beside the speaker's intention is accidental for which reason it cannot be a specific difference. If, on the other hand, one utters' falsehood formally, through having the will to deceive, even if what one says be true, yet inasmuch as this is a voluntary and moral act, it contains falseness essentially and truth accidentally, and attains the specific nature of a lie.That a person intends to cause another to have a false opinion, by deceiving him, does not belong to the species of lying, but to perfection thereof, even as in the physical order, a thing acquires its species if it has its form, even though the form's effect be lacking; for instance a heavy body which is held up aloft by force, lest it come down in accordance with the exigency of its form. Therefore it is evident that lying is directly an formally opposed to the virtue of truth.
Reply to Objection: 1. We judge of a thing according to what is in it formally and essentially rather than according to what is in it materially and accidentally. Hence it is more in opposition to truth, considered as a moral virtue, to tell the truth with the intention of telling a falsehood than to tell a falsehood with the intention of telling the truth.
2. As Augustine says (De Doctr. Christ. ii), words hold the chief place among other signs. And so when it is said that "a lie is a false signification by words," the term "words" denotes every kind of sign. Wherefore if a person intended to signify something false by means of signs, he would not be excused from lying.
3. The desire to deceive belongs to the perfection of lying, but not to its species, as neither does any effect belong to the species of its cause.
Summa Th. II-II EN Qu.108 a.2