Matthew 23:33 " You serpents, you offspring of vipers, how will you escape the judgment of Gehenna?"
Notice that Jesus was asking a rethorical question, not making a statement. The Pharisees could STILL escape Gehenna, however their stubborn resistance to the teaching of Jesus wasn't a good sign. Should they continue in that path, they would surely perish eternally.
Notice the interesting comparison with John, the Baptizer, four years before, adressing those who came to him to be baptized: " John said to the crowds coming out to be baptized by him, "You brood of vipers! Who warned you to flee from the coming wrath? Produce fruit in keeping with repentance. And do not begin to say to yourselves, 'We have Abraham as our father.' For I tell you that out of these stones God can raise up children for Abraham." (Luke 3:8)
The Pharisees didn't heed the warning from John. When Jesus told them that the truth would set them free, they replied: "We are Abraham's descendants and have never been slaves of anyone. How can you say that we shall be set free?" (John 8:32, 33) They did not understand that they were slaves to sin; They failed to see that they needed to repent from their sins and embrace the message of Christ, the Messiah that they ought to have recognized.
So we can see that the potential "unforgivable sin" of the Pharisees was their unrepentance. The "sin against the Holy Spirit" is the stubborn refusal to repent from sin. While the person is still alive, there is always the possibility to "escape from the judgement from Gehenna", through repentance. But once the person dies, if he dies unrepentant, there isn't anything more than the Holy Spirit can do for the person. Jesus could see the unrepentant nature of the Pharisees. He gave them clear warning that they were paving their way into Gehenna. To sin "against the Holy Spirit" is to refuse the help and power of the Holy Spirit to repent from sin, beg for forgiveness, and turn to God. Naturally, that can only be verified once the person dies, hence the reason why no human can judge other as to the "unforgivable sin" has been commited or not.
Eden