"Un-Compounding" Certain Mortal Sins


I was (am) under the impression that there are certain sins that can never be mortal -- namely, sins that are not of a grave nature and therefore can't meet that one objective criterion for mortal sin.

It's not hard to imagine a (usually) non-grave sin -- for example, a lie -- as having manifest grave consequences and somehow entailing mortal sin. But perhaps such sins are best understood as a sort of compound sin, entailing both a falsehood intended to deceive (i.e., a lie) and a separate intention of "grave injury to the virtues of justice and charity," i.e., the mortal sin.

It's tricky because the catechism seems to make clear that a lie can be mortally sinful (par. 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."

I'm not convinced that this rules out an understanding of a lie as strictly being always venial, and the key may be the words "in itself": The lie itself may always only constitute venial sin, and the "it" which clearly *can *constitute mortal sin and which does in fact refer to the lie (but perhaps loosely enough) may be referring to this sort of compound sin.

Thoughts? Objections?



Note that it says IF:

"If a lie in itself only constitutes a venial sin..."

It does not say a lie is always only venial in itself and made mortal by grave injury. A lie can be grave matter, such as perjury. Perjury is always considered grave matter in itself, regardless of injury, circumstances, etc.

I'm not sure I understand what your actual question is. Could you clarify?


"It's all right for us to have sex because I love you."

"No, I have never cheated on you."

"Yes, she has been cheating on you."

"Yes, I'm sure it's not loaded."

"No, he wasn't with me during the time the murder was committed." (even if not under oath)

"Jesus is not really God."

I would think that any of these might be mortal sins if a person knew he was lying when he said them, regardless of his intentions at the time. I'm sure a lot of people have said the second one, for example, from some idea of "sparing the person pain." But a lie like that could easily be grave matter, given "the nature of the truth it deforms." And the last, again if the person knows he is lying, would I think always be grave matter regardless of other circumstances.



"No, those pants don't make you look fat" is not a mortal sin, even if the pants make him/her look like a sausage.

Misrepresenting the truth in a serious matter is a mortal sin.


The catechism doesn’t say “when a lie only constitutes venial sin,” as if to imply that a lie can constitute (in itself) grave matter and therefore mortal sin: It says “if,” which to me reads more as something of an admission of uncertainty about whether a lie in itself can ever constitute grave matter. Accordinly, it would seem to allow for this way of understanding things like perjury as being compound sins and therefore not being completely constituted by a lie in itself, but still entailing some other thing which in itself is grave matter and therefore constitutes the graveness of perjury.

I realize that the word “it” in Par. 2484 refers to the lie, but again, the reference may be loose enough that we can take it to refer to the whole (compound) act and not the lie in itself, in which case it still allows that a lie, strictly speaking, never can be grave matter (but a lie, as understood as the compound act, can be).

So I guess the heart of my question is whether (such) sins are separable; or must a sin, of its very nature, be constituted by a single act of the will, and are things like perjury sins in this especially strict sense?


Sorry, I'm not trying to be obtuse, but I'm still a little unclear on your question.

I agree that to lie per se is not mortal sin. It is the nature of the lie, its circumstances and/or its consequences that makes it more or less grave.

Some types of lie are always considered grave matter, regardless of consequences. Perjury is one such lie that is always considered grave. Perhaps though it is not the lie itself that is gravely wrong, but that we lie having made an oath not to.

Bearing false witness is grave matter, as defined by the ten commandments. But perhaps it is the harm done to the other that makes it so?

In these cases, the lie is still the sin. The only thing wrong in perjury is the lie told. The circumstances (having made on oath) make it grave, but the lie is the only thing that one actively does wrong in this case. So I don't think the lie can be un-compounded as such. Is that what you were getting at?


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