Retro-Actively Mortal Sins?

So, I’m pretty sure I know the answer to this, but I figured I should get a second opinion.

If you find out afterwards that some action of yours was a mortal sin, but you did not know it at the time. Would you be guilty of mortal sin?

My guess is no because you didnt have full knowledge.

The reason I ask is because I am now thinking some of the things that I use to have a hunch were mortally sinful, turned out are mortally sinful.

I suppose I should go to confession anyway.

Thoughts? Thanks

Obviously it never hurts to go to confession. But the answer to your question is that a sin cannot retroactively become mortal based on your later education.

For a sin to be mortal, three conditions must together be met: “Mortal sin is sin whose object is grave matter and which is also committed with full knowledge and deliberate consent.”
. . . .
Mortal sin requires full knowledge and complete consent. It presupposes knowledge of the sinful character of the act, of its opposition to God’s law. It also implies a consent sufficiently deliberate to be a personal choice. Feigned ignorance and hardness of heart133 do not diminish, but rather increase, the voluntary character of a sin.

Catechism of the Catholic Church ¶¶ 1857, 1859.

The sins in question were not “committed with full knowledge” – which implicitly means full knowledge at the time, yes? You did not commit the sins with full knowledge, so they weren’t mortal.

But you’re still free to bring them up in confession; you’re always allowed to bring up venial sins, too.

Welcome to CAF, and best of luck to you on your journey!

Hi stjohnberchmans,

While Godfollower’s statements would be absolutely correct if you had no idea whatsoever that the sins you were committing were mortal (in other words, if your ignorance was invincible), that does not appear to be the case. It seems that you really suspected that those sins just might be mortal, but did not take the time to find out for sure before you committed them. According to the Catholic Church, this is culpable ignorance, and does not excuse you from mortal sin. Here are the pertaining sections of the Catechism:

"1790 A human being must always obey the certain judgment of his conscience. If he were deliberately to act against it, he would condemn himself. Yet it can happen that moral conscience remains in ignorance and makes erroneous judgments about acts to be performed or already committed.
1791 This ignorance can often be imputed to personal responsibility. This is the case when a man "takes little trouble to find out what is true and good, or when conscience is by degrees almost blinded through the habit of committing sin.“59 In such cases, the person is culpable for the evil he commits.”

Jimmy Akin also wrote a great post about the three conditions for mortal sin. I’ve included a pertinent section, but I would definitely recommend reading the whole thing–I certainly found it enlightening! (Here’s the link: )

“You sometimes read about a person needing to have “complete knowledge” of the moral character of the act. I think this is misleading because it can make it sound like if you aren’t a thoroughly catechized moral theologian who has thoroughly studied a situation and has all the relevant facts at his fingertips then there is no mortal sin.
Suppose I’m a poorly-catechized ordinary guy who’s out hunting in the woods and I see a shape in the forrest in front of me that I think might be a man, but it might also be a deer. I am not excused from mortal sin if I shoot at it anyway, even though I didn’t know for certain whether I was objectively shooting at a human being or not.
I thus prefer to speak in terms of “adequate knowledge” of the moral character of the act. There are a lot of things that we can know in an intuitive or incomplete way and still be mortally responsible for them. If this were not the case then St. Paul would never have been able to speak in the terms he did in Romans 1 about pagans who “do not have the Law” (i.e., the Torah) and yet are gravely responsible to God for their actions.”

Try to get to confession as soon as you can. Ask your priest if he can hear your confession tomorrow before or after Mass–I’ve done this many times, and the priests have always been more than happy to help! I’ll be praying for you!

A Catholic is not invincibly ignorant but he can be vincibly ignorant. It is encumbant on all Catholics to learn what the Church teaches and not remain in ignorance. A Catholic can never adopt the attitude that ignorance is bliss. It is not and such Catholics can be held accountable.


If I may counsel you to take them to Confession, as you are aware that they are sin. Whether they were mortal sins or not should not be a priority, but the fact that you are aware they are sin. Take them to the Keys and there will be peace about them.

I used to not confess venial sins but have found much solace and peace in doing so.

God bless.

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