Let's say John was baptized as a Catholic as a baby but did not go to Catholic school or receive any religious education at all and his parents did not take him to mass.

As an adult John begins to go to mass by himself. He begins to read some Catholic books and learned that gossip is a mortal sin. He did not know this up until reading it. Does that mean all his past gossips are considered to be venial sins? If he gossips after reading the material is it then a mortal sin? Or would it only be mortal after a priest has educated him as to why it's a sin?

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    @Grasper Comments are not for answering questions, carrying on theological discussion, or giving personal advice. Please desist using them for those purposes.
    – Caleb
    Commented Oct 17, 2016 at 15:54

2 Answers 2


Mortal sin (from mors = death) forfeits sanctifying grace and is the supernatural death of the soul. St. Augustine defines it as "something said, done or desired contrary to the eternal law."

To be a mortal sin, these conditions must be satisfied:

  1. Knowledge (either natural or supernatural) of the act's sinfulness (offense to God).

  2. Freely performing the sin.

  3. Grave matter

If you didn't know your act was an offense to God at the time of committing it, then it isn't a mortal sin.

Still, in cases of doubt, you should confess it to a priest, who can help judge if it was mortal.

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    One note I would add. Acts like murder or rape can be known by natural reason alone to be wrong; they would be mortal sins regardless. Things like failure to worship on Sundays are only known to be sinful through revelation; they wouldn't be sinful for someone to whom they hadn't been made known. Commented Oct 16, 2016 at 22:46
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    Also, you could do with a couple of supporting quotes if you could find them. Commented Oct 16, 2016 at 22:46
  • I don't fully agree with this. It is true what you wrote about the definition of a mortal sin. But does it mean that all atheist and unbelievers/sinners are in a state of grace just because they don't have full knowledge of their sinfulness? No. They are dead in their sin. This answer needs to be edited to provide more explanation. I believe he had mortal sin and he lived in mortal sins. Even his uninterest or ignorance of his catholic faith caused him to commit a mortal sin. These sins are often generational and sometimes passed down from parents.
    – Grasper
    Commented Oct 17, 2016 at 13:42
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    @Grasper Sin is the separation from God. Atheism/unbelief is the willful separation of oneself from God. Therefore, atheism/unbelief is the greatest sin, most certainly a mortal sin. (Someone ignorant of God is not the same as someone who knows Him yet rejects Him, as atheists do.)
    – Geremia
    Commented Oct 17, 2016 at 15:21
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    @AndrewAlexander While an interesting question (which maybe you should ask! :-) ) once aware of God and choosing to not believe looks like it fits the criteria, as that is seen by the Church as a grave matter. Commented Oct 18, 2016 at 13:02

Full knowledge does not mean that the person explicitly recognizes an act as mortal sin, but that he is or should be aware that the act is seriously wrong. Choosing to be ignorant about the moral character of an act in no way diminishes the person’s responsibility for the act.

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’ (GS, 16). In such cases, the person is culpable for the evil he commits (CCC, no. 1791).

Man not only has a conscience to guide him, but a responsibility to properly inform that conscience. While “ignorance of Christ and His Gospel, bad example given by others, enslavement to one’s passions, assertion of a mistaken notion of autonomy of conscience, rejection of the Church’s authority and her teaching, lack of conversion and of charity” can lead to erroneous judgments of conscience, they do not necessarily constitute invincible ignorance (CCC, no. 1792). Invincible ignorance means that the person is not responsible for their lack of knowledge. It is only this type of ignorance that makes the person not responsible for his morally evil act. However, even in this case, the act “remains no less an evil, a privation, a disorder” ( CCC, no. 1793).

The meaning of man being made in the image of God does not end, however, with reason and will. Man is, by his very nature, made for relationship with God. The missionary mandate is to bring man into full relationship with God. Therefore, to neglect Christ’s mandate is to neglect our fellow man.


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