Can you sin without knowing it?

I’m talking about venial sins. For example. If one grew up in a culture where abortion was considered a simply procedure much like removing a wart and thought nothing wrong in having one. Their parents got abortions their siblings all got abortions it was common every day occurrence in their culture for 100 of years. Would they have committed a sin if they get one? I agree they would have committed a great evil, but is it a personal sin they would need to repent of? Especially if after somebody explained to them the great evil of abortion and they agreed and never had another one. Would they need to confess the abortion prior to knowing it was a great evil?

Another example. As a former Protestant I presumed upon God to know for sure I was going to be united forever to Christ and participate in the beatific vision. I believe all my future sins where forgiven because I said the “sinners prayer”. But once I came to the Catholic faith I understood this was a grave error prideful error on my part. Was I sinning in this belief?


Was it know in the conscience? Was reasonable effort made to find out the truth? If a person comes to know something is sin then it should be avoided in the future, and penance can be done to help remove any attachment to that sin.

A person can commit an act which is a sin, and then their guilt may be mitigated by circumstances, but I think once they realize it is a sin, they should (if Catholic or upon becoming Catholic without having previously been baptized) confess the sin, perhaps by saying, Father, I committed this grave sin (naming the sin, of course) not knowing it was a sin or the seriousness of the sin, in the sacrament of Confession.

If you believe you were prideful in your previous belief, then confess it. I am not sure it is necessarily prideful to have believed that.

In a theoretical extreme case, where a person had absolutely no understanding that he or she was committing a sin, then that person would not be culpable for their actions. Of course, this is an almost impossible scenario to achieve in practice, but there is likely some form of mitigation present for most people.

It gets down to the idea that everyone, being in the image and likeness of God, has some innate sense of right and wrong, and so should feel some pang of conscience upon committing a sin. In the case of a serious sin like abortion, the lack of full knowledge may prevent the sin from being a mortal one, but a person will still be judged in proportion to how much they could understand the evilness of the act.

As for confession, you should confess any sins you remember, including those you realized after the fact.

Well that is one loaded question, venial sins then abortion without skipping a bit. However lets clarify, when GOD did not manifest directly HIS will to people HE still has instilled in every human being a conscience which informs us of the “natural law” a law that comes directly from GOD.
People can heed or accept the guidelines of their conscience, it is called free will. What tends to happen is that if one gets used to never listen to his/her conscience its voice becomes softer and softer until one cannot hear it any longer. When that person comes to the presence of Jesus his/her conscience will be there too and then we will have to confront it.
Now if by the grace of GOD they come to know HIM and HIS son then praise the Lord they will have a better chance to undo the bad things, habits committed prior to this.
And by the way, welcome to Catholic Church, and no you were not sinning since you were misinformed, you did not know better.


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Killing another human being through abortion is grave matter. It’s a bad example to use for “venial sin”, not only because grave matter usually isn’t the stuff of venial sins, but also because even pagans and unbelievers often don’t go marching in to have an abortion like they’re getting a wart removed. There’s an emotional dimension to the act of a woman getting rid of her baby, partly because it’s against the natural order that promotes propagation, partly because there is often an emotional dimension to the act which begat the child. Even if someone thinks it’s morally okay to abort, they tend to consider it a somewhat big deal.


Yes you can sin ‘without knowing it’. God gives everyone a conscience whether you are a Christian or not. If you choose to ignore your conscience repeatedly then it will appear as if you don’t know it but really it’s because you aren’t listening to your conscience. If you listen to little children playing you’ll see this they know what’s wrong and right to a large degree. Sure a conscience needs to be formed and it can be wrongly formed by society and/or poor parenting and this will mitigate our culpability but generally a sin is a sin and we know it, even if we’ve chosen to ignore it. God will balance these all one day. If we become aware of a previous sin (obviously this would be by Gods grace) we should immediately apologise to God and then take it to confession and/or mass when we are able to.

Acts committed without knowledge of sin are something one is not culpable for.

A three year old may steal a cookie or tell a lie, they are not guilty of sin

Check out the catechism CCC section 1854 and 1859. The latter is about mortal sin; however the point I am raising is about the need for adequate knowledge, consent and the issue or “matter” has to be immoral.

There might be a section on partial or reduced culpability.

For example, if a good person is kidnapped, forcibly injected with an hallucinogenic drug, given a gun and dropped off at a fast food restaurant, there would be greatly reduced or no culpability for the resulting actions–as sad as they likely would be.

I can’t believe this thread. No, you cannot sin without knowing it. It’s like asking if you can eat without food. You can’t. In some cases can a person be culpable for not knowingly something? Sure. We don’t have carte Blanc to bury our heads in the sand. It would be sinful to TRY to avoid learning about the Church’s teachings on sin in order to avoid knowing & being responsible for what you know. But barring this - in a situation in which you genuinely believe you are doing a morally-fine thing… zero personal sin even if the action itself is objectively sinful!

Right now I have a baby crawling all over me & babbling loudly. It’s the middle of the night but she was fussy so here we are. Is she sinning? Of course not. Would my ten year old be sinning if she walked into my room talking loudly and trying to get my attention in the middle of the night every night? Yes because I have a rule about disturbing me in the middle of the night - it better be an emergency! Mom needs sleep! But this baby doesn’t know that. And I don’t expect her to. Let’s remember that God is a good FATHER. Why in the world would he have expectations for knowledge on someone who, in good faith, did. not. know. ?? Lets have more trust in the fatherliness of our God! Now it can be a sin for legitimate authority figures if they know but don’t communicate what they know - think the Grand Inquisitor from Dostoyevsky‘s book or, oh I don’t know, authority figures that go around muddying up the waters about moral issues surrounding marriage when their position of authority makes them a rightful teacher to the people…

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Negligence is sinful. God gave man an intellect. The intellect is ordered to truth. If one ignores his natural desire to discover moral truth, he is culpable for sins that result.

From the CCC 1736:
An action can be indirectly voluntary when it results from negligence regarding something one should have known or done: for example, an accident arising from ignorance of traffic laws.

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You are talking about children. That is not the same thing they are yet unformed…Even society doesn’t recognise them as culpable. Not that those things would necessarily be sinful anyway.

As for what is sinful do you not think that people in the world who fornicate with whoever they like not thinking it’s a sin thinking it’s their right to do with their bodies as they like… do you not think that offends God? Do you not think that people acting on same sex attraction but justifying it because society thinks it’s ok cos it’s the way they are made etc. Do you not think that offends God? These are sins and they are done without them knowing it because repeated sin has dulled their intellect. I assure you that’s its possible to sin without knowing it, though people ought to know it as they have a conscience but they are merely ignoring it. That is why people in general are so unhappy. Go down the 10 commandments and see if the world does any of them. Of course they do. Next time you’re in a busy place count how many times you hear the Lord’s name taken in vain. That’s a sin and it’s so common I sometimes wish I could turn my hearing off, yet people dont know they are doing it. Sadly many don’t care.

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Thanks everyone for the reply’s. For the most part I think this is healthy discussion. I wonder if it would be helpful to make a few distinctions.

What is the difference between personal sin and something that is intrinsically evil? If someone does something intrinsically evil is it always a personal sin?

Example. Would destroying the planet with a nuclear weapons be intrinsically evil? I believe it is, but is it always a personal sin that someone needs to be accountable for if done? For example. What if you where told to push this red button to get a free ice cream cone but it actually released enough nuclear missiles to destroy the earth. Your act committed a great evil but was it a personal sin? Does your ignorance of the actual effect of pushing the red button disqualify you from a personal sin?

Devils tempt people the flesh and deceive it is not sin by law, media or other powers to subdue people.

Refer to Timony 3:1-5, to understand all the world have lost sense of many sins.

In 1960s, they allowed dishonoring parents for over 18 years old because they wanted more soldiers for VN war. Nobody feel it is sin any more because of legitimate authorized. Same as abortion, gay marriages, satanist church’s attendance…

However, when people strictly obey God’s orders then they realize the sins at once. Will realize the abortion is the murder of the unborn child; etc.

You sound angry and I’m not sure why. If people had all the answers, there wouldn’t be much of a need for these forums. It sounds like the OP has not always been Catholic and has come here to gain a better understanding of what Catholics believe. Let’s treat him and his question with respect.

Yes. The person who deceived you is the one who sinned.

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Oh I wasn’t bugged by the OP… just by the concept that he’s being told to confess things that are accidents! I feel he’s being encouraged towards scrupulosity and that frustrates me. Being scrupulous isn’t holier.

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Yup. It does.

Pope Pius XII spoke a prophetic word: “Perhaps the greatest sin in the world today is that men have begun to lose the sense of sin.”


Well, I’m not disagreeing. However moral OCD / scrupulosity is ALSO a loss of the sense of sin. Asking if someone is personally responsible for something they did with zero knowledge / understanding… sounds like scrupulosity to me. I am all about people forming a correct sense of sin, but that avoids both the pitfall of seeing sin nowhere & seeing sin where it… isn’t.

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