How then do we illustrate the sin against the Holy Spirit as opposed to a sin against the Father or against the Son? We ought to know what the sin consists of so as to avoid it. We have to take Jesus’ words literally, that some sins will not be forgiven, either in this world or in the next. Was Judas, for example, guilty of a sin against the Holy Spirit? Is this why Jesus tells him it would be better for him had he never been born? But on the surface it appears that Judas’ sin was against the Son, which was forgivable. In what way could it have been also against the Holy Spirit? Was it the despair that followed the sin, and the suicide that followed the despair, that offended the Holy Spirit? Was it that Jesus knew the willingness of Judas to be doomed by his own sins instead of repenting them, as Peter had repented his denial of knowing Jesus and Paul had repented his persecution of Christ?
What’s graver was that Judas despaired of God’s mercy and thereby killed himself. It was his despair and suicide that was much worse. He could have easily repented and gained forgiveness if he has just simply done this.
Now, the sin Jesus was taking about in Matt 12:31 is commonly called “the unforgivable sin” either because of the following different interpretations…
A) It’s a sin that is less likely to be forgiven due to its malice and hardness of heart (like those of the Pharisees) and one that will cause God’s wrath in this world and the world to come.
B) The unforgivable sin that Jesus was talking about here was not a declaration of their (the Pharisees) being unforgivable but rather a warning that if they persist in this state of sin and blasphemy they will die that way and hence be unforgivable. This is also known as “final impenitence” and it’s the interpretation that St. Augustine, the Catechism of the Catholic Church and I tend to lean towards.
C) The third interpretation is that blasphemy against the Holy Ghost is any sin which removes anything that is directly necessary for forgiveness: like the sin of despair removes hope, hence a person in that state cannot be forgiven while he remains in that state. St. Thomas Aquinas uses the analogy of a sick man refusing all or any means that will help him get back to health and thereby is incurable through his own fault.
All of these are said to be special “sins against the Holy Spirit” because they directly go against the Holy Ghost who is the main Divine Person we attribute forgiveness of sins to. A lot of things can be “sins against the Holy Spirit” but the kind Jesus was taking about was a special case where the person either cuts off all means of forgiveness due to the circumstances of his sin or harness of hear, or he keeps on sinning until he dies that way.
All in all the church teaches that there is no sin that can be committed, if truly repented of, that cannot be forgiven by the power of Jesus Christ’s blood through the sacramental keys of Confession.
If a person commits the unforgivable sin it is because He refuses the forgiveness, not God.