He who blasphemes against the Holy Spirit will not be forgiven
In today's gospel Jesus teaches us among other things, the possibility of an unforgivable sin. "Everyone who speaks a word against the Son of Man will be forgiven, but the one who blasphemes against the Holy Spirit will not be forgiven." What is this sin that is beyond the mercy of God?
To understand this passage, we need to read what comes before it, as well as other parallel passages in the synoptic gospels. Jesus said this soon after the Pharisees and Scribes had contended that the mighty works he was performing were due to the power of the devil. With this background we can understand what is stated in the Catechism of the Catholic Church Paragraph 1864 about the eternal sin: "there are no limits to the mercy of God, but anyone who deliberately refuses to accept his mercy by repenting, rejects the forgiveness of his sins and the salvation offered by the Holy Spirit."
William Barclays explains so clearly the mechanism behind the "eternal sin". He says: "...we can lose the faculty of recognizing God. By repeatedly refusing God's word, by repeatedly taking our own way, by repeatedly shutting our eyes to God and closing our ears to him, we can come to a stage when we do not recognize him when we see him, when to us evil becomes good and good becomes evil. That is what happened to the scribes and Pharisees. They had so blinded and deafened themselves to God that when he came they called him a devil.
Why is that the unforgivable sin? Because in such a state repentance is impossible. If a man does not even realize that he is sinning, if goodness no longer makes any appeal to him, he cannot repent. God has not shut him out; by his repeated refusals he has shut himself out.
