Blasphemy against the Holy Spirit - the one unforgivable sin. What is it?
I suggest that blasphemy against the Spirit might be similar to God “hardening Pharaoh’s heart” – which was not so much God turning Pharaoh bad as God allowing Pharaoh to settle in the badness he had chosen.
I think a man who makes a positive choice to affirm evil in his life and to cease struggling against it, to opt for it as his greatest good, is committing blasphemy against the Holy Spirit, and so we see the results – not only his being unforgiven, but being unforgivable because he no longer desires to be forgiven.
Final impenitence is the fruit of this attitude. The unforgiven state is the state of the calloused soul that results from this blasphemy - this blasphemy being a lifelong act, not an unguarded moment of anger or frustration.
Think of certain sinners whose sins have become ontologically a part of who they are - inveterate pedophiles, sodomites devoted to the lifestyle, serial adulterers. Yes, repentance may be possible in any of the above cases, unless the evil the sinner serves has become his god - his greatest good; unless he begins to live for that and to sell his soul to it. It is then, when we have said to the Goodness of God, "To hell with you," that we have kicked God's Spirit out of our lives, and in His mercy He allows us to live and die unforgivable and unforgiven - in other words, to get what we want.
When you think about it, the psychology of Scripture is far more insightful than the pop psychology of our day.
And may the Holy Spirit keep us from blasphemy against Him.