2388. Vices Opposed to Truthfulness.—(a) By defect one sins against truth through lying and breach of promise; (b) by excess one sins against truthfulness in violation of secret or other unjustifiable disclosures.
2389. Lying.—A lie is a word spoken with the purpose of stating what is not true.
(a) It is said to be a word, by which is meant any external sign consisting in speech or its equivalent. A lie may be expressed by language, oral or written, by signs, by gestures, by insinuation, by expressive silence, by actions or conduct (see 2012, 2028).
(b) A lie is spoken, that is, expressed externally. But the guilt is found in the will, and hence those who plan lies are guilty of mendacity, even though they do not carry out their plans.
(c) A lie is told with purpose; that is, there is a comparison by the intellect of the sign with the thing signified and a voluntary choice of the insufficient sign to be used. An infant or an unconscious person, therefore, may tell an untruth, but he cannot tell a lie. Moreover, a person who has no good command of language or no clear understanding of a subject is not guilty of lying when in spite of his efforts to the contrary he gives misleading impressions. But those who do not think before they speak, or who use language carelessly or inaccurately, may be guilty of injustice and deception, or even of indirect lying.
(d) The purpose of a lie is the statement of what is not true, or the pretense that what is not in one’s mind is in one’s mind. Just as truth is the agreement of the word with the thought, so a lie is the disagreement of word with thought. But a lie need not be entirely false, and indeed one of the most dangerous of lies is what is known as a half-truth, in which some real facts are told in order to give support to pretended facts, or in which valid arguments are adduced to throw dust in the eyes as regards other arguments that are sophistical.
2390. Statements Liable to Misunderstanding or Misinterpretation.—A word that sufficiently expresses one’s idea is not a lie or a deception, even though another idea will be taken from it by a listener or is conveyed by its mere letter.
(a) Thus, misunderstanding due to defect, not of the speaker, but of the listener, does not make one’s words untruthful, any more than it makes them scandalous (see 1462), as when the listener has not given attention to what was said (John, xxi. 23). Even a speech worded obscurely because the matter is obscure, or because the listener would be harmed by plainer speech (see 1001), is not mendacious but prudent.
(b) Misinterpretation to which a statement is open on account of its wording does not make the statement untruthful, if the context or circumstances sufficiently disclose the true meaning of the words. Examples: hyperbolical, ironical or other metaphorical speech; words spoken in jest or in terms of customary politeness, such as “your most obedient servant”, statements made inquiringly or hypothetically (e.g., when a judge or prosecutor accuses a defendant of crime in order to discover the truth; cfr. Gen., xiii. 9), or by way of mere quotation or of fictitious narrative (e.g., fairy tales, stories, reveries), or of disputation as in school debates exercised for the sake of practice in argumentation. It is not a lie to write under a pen-name, to speak according to the personality one represents (Gen., xxxi. 13; Tob., v. 18), to answer according to the mind of a questioner, as when A says to B: “Have you seen your father?” meaning, “Do you know where he is?” and B replies: “I have not seen him,” meaning “I do not know where he is.” Lying contests, in which fishermen, sportsmen, etc., vie with one another to see who can tell the most incredible yarn or tall tale, are not in themselves sinful, but there may be circumstances (for example, scandal, deception, danger) that make them reprehensible.
2391. Divisions of Lies.—(a) Intrinsically, or in respect to its nature as a departure from the speaker’s mind, every lie is either an exaggeration, which tells more than the truth, or a suppression, which tells less than the whole truth. He who affirms what he does not believe, or who states as certain what he thinks is uncertain, exaggerates; he who denies what he believes, or who states as doubtful what he holds as certain, is guilty of suppression.