Q. A teacher told my child he was in mortal sin for telling a lie (a small lie, of omission). Are small lies mortally sinful?
A. First, I want to apologize that a teacher misapplied the term mortal sin to what was, according to your question, a venial sin; also, I’m glad you asked this question, as it is a good opportunity to distinguish mortal sin from venial sin. This is something every Christian should know well.
A mortal sin, by its very nature, is something serious: it separates a person from friendship with God, it is a grave violation of God’s commandments, and if unrepented, leads to eternal separation from God, that is, hell (cf. CCC 1855, 1861). For an action to be a mortal sin, three criteria are necessary: 1. grave matter; 2. full knowledge; and 3. deliberate consent (cf. CCC 1857).
Sadly, mortal sins are not uncommon. Nevertheless, it is very important for the formation of one’s conscience to distinguish a mortal sin from a venial sin, as venial sins are far more common and, even for the very holy, are not entirely avoidable. Venial sins hurt but do not break our friendship with God, they wound but do not destroy charity, and they merit temporal but not eternal punishment. Venial sins occur when there is less serious matter, or when one “disobeys the moral law in a grave matter, but without full knowledge or without complete consent” (CCC 1862).
Let’s use the various kinds and degrees of lying to illustrate this distinction. Every lie, that is, false speech with the intent to deceive, is against the 8th Commandment. Therefore, every lie is a sin. Yet, not every lie constitutes grave matter. In fact, “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” (CCC 2484).
Some clear examples of grave matter with regard to the 8th Commandment are: lying or omitting an essential fact under oath; serving as a false alibi for something criminal or serious; lying or omitting an essential fact in a serious matter to an authority who has the right to know, e.g., to a police officer or school administrator who is collecting facts about alleged sexting, drugs, underage drinking, etc. Each of these examples constitutes grave matter. Yet, a mortal sin includes not only grave matter but also full knowledge and complete or deliberate consent.
For example, a young child may not understand the gravity of an oath; in this case there may not be full knowledge if he intentionally omitted an import fact under oath. Likewise, an adolescent who is speaking falsely out of fear or duress to a school administrator about alleged sexting might not have complete or deliberate consent. In these cases, if full knowledge or complete consent are truly missing—i.e., it is not actually feigned ignorance or hardness of heart—then it is not a mortal sin. Yet the matter is still serious, and it is still a sin. If all three elements are present, then it is a mortal sin.
On the other hand, there are numerous examples of lying that do not constitute grave matter: objectively presenting one’s talents in sports as greater than they really are (boasting); attributing motivations to another’s misbehavior in the workplace without a clear foundation (rash judgment); speaking of or repeating another’s faults or supposed faults to one’s friends without a valid reason (gossip); overstating or misrepresenting a case in correcting a student in class (officious lies); speaking falsely in small matters to a parent or teacher to get out of trouble (so-called “emergency” lies), etc. All of these particular examples are venial sins for which repentance is needed. Nevertheless, these sins are still essentially different from a mortal sin, since they do not include grave but less serious matter.
This question was answered by a priest of the Diocese of Lincoln. Write to Ask the Register using our online form, or write to 3700 Sheridan Blvd., Suite 10, Lincoln NE 68506-6100. All questions are subject to editing. Editors decide which questions to publish. Personal questions cannot be answered. People with such questions are urged to take them to their nearest Catholic priest.
