EXHORTATION, 1. In order to avoid the vice of lying, (a) let us be careful in small matters regarding the truth; (b) let us avoid all unnecessary loquacity; (c) let us always remember that insincerity is hateful both to God and man (Ecclus. vii. 14; Wis. i. li; Prov. xii. 22; Ecclus. xx. 26). 2. Parents should train their children to be scrupulously truthful.
Catechism of the Council of Trent, Part III
THE SIN OF LYING
To all conscientious persons is addressed the divine command that in all their intercourse with society, in every conversation, they should speak the truth at all times from the sincerity of their hearts; that they should utter nothing injurious to the character of another, not even of those by whom they know they have been injured and persecuted. For they should always remember that between them and others there exists such a close social bond that they are all members of the same body.
THE MALICE OF LYING
In order that the faithful may be more disposed to avoid the vice of lying, the pastor will place before them the extreme lowness and disgrace and turpitude of this sin. In the Sacred Scriptures the devil is called "the father of lies"; for as, "he stood not in the truth, he is a liar and the father thereof."(1)
But to banish from amongst the faithful so great a sin, the pastor will add the mischievous consequences of which this vice is the source. These consequences are without number; and the pastor, therefore, must be content with pointing out the chief kinds of evil and calamity that are caused by lying.
In the first place, he will inform them how grievously lies offend God and how deeply a liar is hated by God. "Six things there are," says Solomon, "which the Lord hateth, and the seventh his soul detesteth: haughty eyes, a lying tongue, hands that shed innocent blood, a heart that deviseth wicked plots, feet that are swift to run into mischief, a deceitful witness that uttereth lies, etc." (2) Who, then, can protect or save from severest chastisements the man who is thus the object of God's special hate?
Again, what more wicked, what more base than, as St. James says, "with the same tongue, by which we bless God and the Father, to curse men, who are made after the likeness of God," so that "out of the same fountain flows sweet and bitter water."(3) The tongue, which was before employed in giving praise and glory to God, afterwards, as far as it is able, by lying treats the Author of truth with ignominy and dishonor. Hence, liars are excluded from a participation in the bliss of heaven. To David asking, "Lord! who shall, dwell in thy tabernacle?" the Holy Spirit answers: "He that speaketh truth in his heart, who hath not used deceit in his tongue." (4) Lying is also attended with this very great evil that it is an almost incurable disease. For since the guilt of the calumniator cannot be pardoned, unless satisfaction be made to the calumniated person, and since as we have already observed, this duty is difficult for those who are deterred from its performance by false shame and a foolish idea of dignity, it follows that he who continues in this sin perseveres in a course which must ultimately lead to the unending punishments of hell. Let no one indulge the delusive hope of obtaining the pardon of his calumnies or detractions, until he has repaired the injury which they have inflicted, whether this was done in a court of justice or in private and familiar conversation.
But the evil consequences of lying are widespread and extend to society at large. By duplicity and lying good faith and truth, which form the closest links of human society, are dissolved, confusion ensues, and men seem to differ in nothing from demons.
The pastor will also teach that loquacity is to be avoided. By avoiding loquacity the other evils of the tongue will be obviated, and a preventive opposed to lying, from which loquacious persons can scarcely abstain.
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