Today’s Catechism sections discuss respect for the truth. Supporting material comes from St. Augustine’s “On Lying”.

IV. Respect for the Truth

2488 The right to the communication of the truth is not unconditional. Everyone must conform his life to the Gospel precept of fraternal love. This requires us in concrete situations to judge whether or not it is appropriate to reveal the truth to someone who asks for it.

2489 Charity and respect for the truth should dictate the response to every request for information or communication. The good and safety of others, respect for privacy, and the common good are sufficient reasons for being silent about what ought not be known or for making use of a discreet language. The duty to avoid scandal often commands strict discretion. No one is bound to reveal the truth to someone who does not have the right to know it.282

2490 The secret of the sacrament of reconciliation is sacred, and cannot be violated under any pretext. "The sacramental seal is inviolable; therefore, it is a crime for a confessor in any way to betray a penitent by word or in any other manner or for any reason."283

2491 Professional secrets - for example, those of political office holders, soldiers, physicians, and lawyers - or confidential information given under the seal of secrecy must be kept, save in exceptional cases where keeping the secret is bound to cause very grave harm to the one who confided it, to the one who received it or to a third party, and where the very grave harm can be avoided only by divulging the truth. Even if not confided under the seal of secrecy, private information prejudicial to another is not to be divulged without a grave and proportionate reason.

2492 Everyone should observe an appropriate reserve concerning persons' private lives. Those in charge of communications should maintain a fair balance between the requirements of the common good and respect for individual rights. Interference by the media in the private lives of persons engaged in political or public activity is to be condemned to the extent that it infringes upon their privacy and freedom.

IN BRIEF

2510 The golden rule helps one discern, in concrete situations, whether or not it would be appropriate to reveal the truth to someone who asks for it.

2511 "The sacramental seal is inviolable" (⇒ CIC, can. 983 # 1). Professional secrets must be kept. Confidences prejudicial to another are not to be divulged.

In “On Lying”, St. Augustine discusses whether there are circumstance where it is allowable to lie for a good purpose.

5. But whether a lie be at some times useful, is a much greater and more concerning question. Whether, as above, it be a lie, when a person has no will to deceive, or even makes it his business that the person to whom he says a thing shall not be deceived although he did wish the thing itself which he uttered to be false, but this on purpose that he might cause a truth to be believed; whether, again, it be a lie when a person willingly utters even a truth for the purpose of deceiving; this may be doubted. But none doubts that it is a lie when a person willingly utters a falsehood for the purpose of deceiving: wherefore a false utterance put forth with will to deceive is manifestly a lie. But whether this alone be a lie, is another question. Meanwhile, taking this kind of lie, in which all agree, let us inquire, whether it be sometimes useful to utter a falsehood with will to deceive. They who think it is, advance testimonies to their opinion, by alleging the case of Sarah, who, when she had laughed, denied to the Angels that she laughed: of Jacob questioned by his father, and answering that he was the elder son Esau: likewise that of the Egyptian midwives, who to save the Hebrew infants from being slain at their birth, told a lie, and that with God's approbation and reward: and many such like instances they pick out, of lies told by persons whom you would not dare to blame, and so must own that it may sometimes be not only not blameworthy, but even praiseworthy to tell a lie. They add also a case with which to urge not only those who are devoted to the Divine Books, but all men and common sense, saying, Suppose a man should take refuge with you, who by your lie might be saved from death, would you not tell it? If a sick man should ask a question which it is not expedient that he should know, and might be more grievously afflicted even by your returning him no answer, will you venture either to tell the truth to the destruction of the man's life, or rather to hold your peace, than by a virtuous and merciful lie to be serviceable to his weak health? By these and such like arguments they think they most plentifully prove, that if occasion of doing good require, we may sometimes tell a lie.

6. On the other hand, those who say that we must never lie, plead much more strongly, using first the Divine authority, because in the very Decalogue it is written You shall not bear false witness; under which general term it comprises all lying: for whoso utters any thing bears witness to his own mind. But lest any should contend that not every lie is to be called false witness, what will he say to that which is written, The mouth that lies slays the soul: and lest any should suppose that this may be understood with the exception of some liars, let him read in another place, You will destroy all that speak leasing. Whence with His own lips the Lord says, Let your communication be yea, yea; nay, nay; for whatsoever is more than these comes of evil. Hence the Apostle also in giving precept for the putting off of the old man, under which name all sins are understood, says straightway, Wherefore putting away lying, speak ye truth.

Footnotes

282 Cf. ⇒ Sir 27:16; ⇒ Prov 25:9-10.
283 ⇒ CIC, Can. 983 # 1.