(c) It regulates the expression of the mind, that is, the words, writing, gestures, conduct, and other external signs, so as to make them conformable to the mind which they stand for. Truthfulness deals with internal things (e.g., when the speaker says that he has good health or is well disposed towards another) and with external things as they appear to the speaker (e.g., when he says that he is certain or believes that a report is accurate).
(d) It is a faithful expression of what is in the mind or belief. Hence, one may be truthful while making statements contrary to fact, or untruthful while making statements agreeable to facts, for truthfulness is sincerity, not correctness.
(e) It is a due expression of one’s mind or belief; that is, it is given when and where and as it should be given. A person who speaks out his mind on all occasions, with no regard for results, is not a liar, but he is at least imprudent, and he cannot be said to possess the virtue of truthfulness, for every virtue is prudent. Examples of this are persons who unnecessarily indulge self-praise by telling their true virtues or perfections (Prov., xxvii. 2), or who vaingloriously or otherwise foolishly publish their true sins or imperfections (Is. iii. 9).
2386. The Excellence of Truthfulness.—(a) Truthfulness is a virtue, since it makes right use of language and other signs by employing them for the truth, and also serves society, which rests on the trust that men have in the words and promises of their fellow-men. St. Paul admonishes the Ephesians (iv. 25) that each one speak the truth to his neighbor, since all are members of the other.
(b) It is a moral virtue, preserving moderation in conversations and other interchanges of thought. This virtue sees that facts are neither exaggerated nor understated, that truth is not manifested when it should be concealed, nor concealed when it should be spoken.
(c) It is a special virtue, for, while the other moral virtues regulate actions and external things, none of them except truthfulness regulates those objects precisely in their character of media or instruments for signifying and conveying thoughts, opinions, and decisions. And since a great part of human life is occupied in conference or correspondence with others, truthfulness is one of the most useful of the virtues and one whose exercise is most frequently called for.
(d) It is a virtue annexed to justice. On the one hand, it is like justice, since it pays a debt which one social being owes another of speaking the truth; on the other hand, it falls short of justice, since the debt is moral, not legal. This is said of truthfulness in ordinary intercourse, for in judicial process and in contracts there is also a legal obligation of justice to tell the truth.
2387. Sincerity and Fidelity.—Two virtues that pertain to truthfulness are sincerity and fidelity.
(a) Sincerity (simplicity) is the virtue of one who is consistent with himself, avoiding duplicity and double dealing of every kind, such as lies, equivocations, sophistries, specious excuses, quibbles, dishonest shifts, distractions, concealments, and the like.
(b) Fidelity (loyalty) is the virtue of one who fulfills promises that are obligatory only in virtue of his word freely given. It differs from constancy, which is concerned not with promises but resolutions, and from virtues concerned with promises that are obligatory in virtue of legal debt, such as contracts, promissory oaths (see 1692, 1749, 1753, 1888). Fidelity makes an honest man’s word as good as his bond, and it is therefore one of the most appreciated of virtues (Matt., xxv. 21; Psalm xiv). Horace calls it the sister of justice.