Thanks. May I ask a question… what would happen if someone never realised that it was a sin? Would they go to hell? (just wondering by the way)
That’s an interesting question, and difficult to answer because the line between knowing and not knowing it is a sin is very fine.
Even if a person does not know that masturbation is a mortal sin according to the Church, they still *know *it is wrong. You see, woven into our natures, as human beings, is the natural law. Our consciences tell us what is right and what is wrong, not overtly like the laws of the Church do, but quietly, in our minds and hearts.
A person who masturbates may not realize it now, and may not fully understand the ramifications of his action, but still has that voice telling him it is wrong. Further, he can often see how the masturbation negatively affects his relations with other people, his understanding of human sexuality, and, if he is married, his marriage.
So, no, I would say that a person can still be held responsible for his sin even if he does not know it is wrong in the eyes of the Church.
(Note: The word “he” is used here, correctly, as the third person singular. It does not restrict what I have said to males, but includes females.)