When is lying a mortal sin?

[nursestephanie]

When is lying a mortal sin? The reason that I ask is the other day at work, I withheld information from my supervisor about a given situation. I did this at the request of a co-worker, who was the cause of an accident at work in which someone got hurt. My supervisor asked me if I knew the details about the accident, and I lied to her and said no to keep the coworker from getting fired. Would this be a mortal sin?

 

[Renton405]

apparently in the bad cases when it damages charity

It breaks the commandment “Thou shall not bear false witness” against they neighbor…

heres from the Summa by St. Thomas

Whether every lie is a mortal sin?

Objection 1. It seems that every lie is a mortal sin. For it is written (Psalm 6:7): “Thou wilt destroy all that speak a lie,” and (Wisdom 1:11): “The mouth that belieth killeth the soul.” Now mortal sin alone causes destruction and death of the soul. Therefore every lie is a mortal sin.

Objection 2. Further, whatever is against a precept of the decalogue is a mortal sin. Now lying is against this precept of the decalogue: “Thou shalt not bear false witness.” Therefore every lie is a mortal sin.

Objection 3. Further, Augustine says (De Doctr. Christ. i, 36): “Every liar breaks his faith in lying, since forsooth he wishes the person to whom he lies to have faith in him, and yet he does not keep faith with him, when he lies to him: and whoever breaks his faith is guilty of iniquity.” Now no one is said to break his faith or “to be guilty of iniquity,” for a venial sin. Therefore no lie is a venial sin.

Objection 4. Further, the eternal reward is not lost save for a mortal sin. Now, for a lie the eternal reward was lost, being exchanged for a temporal meed. For Gregory says (Moral. xviii) that “we learn from the reward of the midwives what the sin of lying deserves: since the reward which they deserved for their kindness, and which they might have received in eternal life, dwindled into a temporal meed on account of the lie of which they were guilty.” Therefore even an officious lie, such as was that of the midwives, which seemingly is the least of lies, is a mortal sin.

Objection 5. Further, Augustine says (Lib. De Mend. xvii) that “it is a precept of perfection, not only not to lie at all, but not even to wish to lie.” Now it is a mortal sin to act against a precept. Therefore every lie of the perfect is a mortal sin: and consequently so also is a lie told by anyone else, otherwise the perfect would be worse off than others.

On the contrary, Augustine says on Ps. 5:7, “Thou wilt destroy,” etc.: “There are two kinds of lie, that are not grievously sinful yet are not devoid of sin, when we lie either in joking, or for the sake of our neighbor’s good.” But every mortal sin is grievous. Therefore jocose and officious lies are not mortal sins.

I answer that, A mortal sin is, properly speaking, one that is contrary to charity whereby the soul lives in union with God, as stated above (24, 12;35, 3). Now a lie may be contrary to charity in three ways: first, in itself; secondly, in respect of the evil intended; thirdly, accidentally.

 

[Greg27]

In my understanding perjury (lying under grave oath to tell the truth) is mortally sinful, if done with full knowledge and consent. Other types of lying are considered less grave.

 

[puzzleannie]

When is lying a mortal sin? The reason that I ask is the other day at work, I withheld information from my supervisor about a given situation. I did this at the request of a co-worker, who was the cause of an accident at work in which someone got hurt. My supervisor asked me if I knew the details about the accident, and I lied to her and said no to keep the coworker from getting fired. Would this be a mortal sin?

a lie is a mortal sin when it is grave matter, when the liar knows it is grave, and does it anyway with full free consent and will. I was not there but objectively an accidental that resulted in bodily injury sounds like grave matter to me.

 

[thistle]

As the previous poster said a grave sin only becomes a mortal sin through knowledge that it is a grave sin and then deliberately committing the sin in that knowledge.

However, not all lies are grave sins.

CCC 2482 “A lie consists in speaking a falsehood with the intention of deceiving.” The Lord denounces lying as the work of the devil: “You are of your father the devil, . . . there is no truth in him. When he lies, he speaks according to his own nature, for he is a liar and the father of lies.”

CCC 2483 Lying is the most direct offense against the truth. To lie is to speak or act against the truth in order to lead someone into error. By injuring man’s relation to truth and to his neighbor, a lie offends against the fundamental relation of man and of his word to the Lord.

CCC 2484 The gravity of a lie is measured against the nature of the truth it deforms, the circumstances, the intentions of the one who lies, and the harm suffered by its victims. If a lie in itself only constitutes a venial sin, it becomes mortal when it does grave injury to the virtues of justice and charity.

CCC 2485 By its very nature, lying is to be condemned. It is a profanation of speech, whereas the purpose of speech is to communicate known truth to others. The deliberate intention of leading a neighbor into error by saying things contrary to the truth constitutes a failure in justice and charity. The culpability is greater when the intention of deceiving entails the risk of deadly consequences for those who are led astray.

CCC 2486 Since it violates the virtue of truthfulness, a lie does real violence to another. It affects his ability to know, which is a condition of every judgment and decision. It contains the seed of discord and all consequent evils. Lying is destructive of society; it undermines trust among men and tears apart the fabric of social relationships.