Omitting a sin that I did not know was mortal


Years and years ago, I’m afraid I went to confession and omitted a sin- which I believed to have been venial in my teens,but see differently now. My catholic radar did not fully develop until my later 20’s, and as such, I believe if I were to commit the sin again with full knowledge, it may be mortal (?).

My question is this: if I did not know it was grave at the time, would it be a venial sin and therefore forgiven with a confession (when the priests absolves you from all your sins)?
If I did not have full knowledge of its grave nature, would it be venial or mortal?

Or do I bring up something from that far back in confession now?

Thanks in advance!


Hm… I’m not really sure. I mean, it’s obviously forgiven, let’s be clear about that much. It is not unforgiven. Even unconfessed mortal sins, if forgotten unintentionally, are forgiven (although I believe you must confess them next time around)

The question is, ought you to confess it, if it were venial? I’m not certain.

If you’re like me, there’s a few things from the past that just haunt you. And if it’s just those types of things, you’re probably better off confessing them. Mine were pretty humiliating. But I confessed them anyways… and I don’t have to worry about that nagging question anymore.

So, think about that: even if you don’t have to confess them, do you think it’s better to do so anyways?


My worry is that I’ve been receiving communion and participating in the church, all the while.


One of the requirements for a sin to be mortal is full knowledge. If you weren’t aware that it was a mortal sin, then you’re not culpable. Rest easy.


First of all, if you honestly did not know that an act was grave matter at a specific time, then the sin was venial. Period. It’s forgiven, forget about it. However, if you were to commit that same sin now (with full will), then it would be a mortal sin. Seriously. A sin needs three things to be a mortal sin:

(a) grave matter - some sins (such as abortion, artificial birth control, masturbation, proclaiming heresy, etc.) are always grave matter, while for others it depends on context (e.g. stealing $1 from most people would probably not be grave matter, but if it’s from a homeless person or a beggar, then it would be);

(b) full knowledge of the gravity of the sin (of course, willfull or feigned ignorance is no excuse, but this is why children under the age of reason are thought to be incapable of committing mortal sins - their consciences are still in the very early stages of being formed - and pretty much distinguish whether an act is right or wrong based on whether or not they get in trouble for it);

© full intent of the will (outside factors can mitigate the will, such as addiction, forced action, mental illness and/or intellectual disability, desperation, coercion, etc.).


You didn’t realize that what you did was grave matter, therefore, you did not commit a mortal sin.

In order to commit mortal sins, we have to actually know that whatever act we are about to commit is morally grave.

For example: I myself have masturbated since the age of 12, and only tried to break the habit when I realized that it is morally sinful 4 years later. Since I didn’t realize that I was committing grave matter, I was committing venial sin.

In this circumstance, you likely committed venial sin, which dams you to Purgatory, but have no fear. Taking the Eucharist worthily, subjecting your body to acts of penance, confession, etc. will wipe away venial sins.



It was forgiven either way, so no worry about past Communion. You can always mention it at your next confession to ease your mind.


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