Blasphemy against the Holy Spirit is the sin committed by the person who claims to have a "right" to persist in evil and who thus rejects Redemption
The unjust hath said within himself, that he would sin : there is no fear of God before his eyes. Psalm 36:1
“Whoever rejects the Spirit and the Blood remains in” dead works”, in sin. “
Dominum et vivificantem:
The Sin Against the Holy Spirit
46. Against the background of what has been said so far, certain other words of Jesus, shocking and disturbing ones, become easier to understand. We might call them the words of “unforgiveness.” They are reported for us by the Synoptics in connection with a particular sin which is called “blasphemy against the Holy Spirit.” This is how they are reported in their three versions:
Matthew: “Whoever says a word against the Son of Man will be forgiven but whoever speaks against the Holy Spirit will not be forgiven, either in this age or in the age to come.”180
Mark: “All sins will be forgiven the sons of men, and whatever blasphemies they utter; but whoever blasphemes against the Holy Spirit never has forgiveness, but is guilty of an eternal sin.”181
Luke: “Every one who speaks a word against the Son of Man will be forgiven; but he who blasphemes against the Holy Spirit will not be forgiven.”182
Why is blasphemy against the Holy Spirit unforgivable? How should this blasphemy be understood ? St. Thomas Aquinas replies that it is a question of a sin that is “unforgivable by its very nature, insofar as it excludes the elements through which the forgiveness of sin takes place.”183
According to such an exegesis, “blasphemy” does not properly consist in offending against the Holy Spirit in words; it consists rather in the refusal to accept the salvation which God offers to man through the Holy Spirit, working through the power of the Cross.
If man rejects the “convincing concerning sin” which comes from the Holy Spirit and which has the power to save, he also rejects the “coming” of the Counselor – that “coming” which was accomplished in the Paschal Mystery, in union with the redemptive power of Christs’s Blood which ” purifies the conscience” from dead works.”
We know that the result of such a purification is the forgiveness of sins. Therefore, whoever rejects the Spirit and the Blood remains in “dead works,” in sin.
And the blasphemy against the Holy Spirit consists precisely in the radical refusal to accept this forgiveness, of which He is the intimate giver and which presupposes the genuine conversion which He brings about in the conscience.
If Jesus says that blasphemy against the Holy Spirit cannot be forgiven either in this life or in the next, it is because this “non-forgiveness” is linked, as to its cause, to non-repentence,” in other words to the radical refusal to be converted.
This means the refusal to come to the sources of Redemption, which nevertheless remain “always” open in the economy of salvation in which the mission of the Holy Spirit is accomplished.
The Spirit has infinite power to draw from these sources: “he will take what is mine,” Jesus said. In this way he brings to completion in human souls the work of the Redemption accomplished by Christ, and distributes its fruits.
Blasphemy against the Holy Spirit, then, is the sin committed by the person who claims to have a “right” to persist in evil – in any sin at all – and who thus rejects Redemption.
One closes oneself up in sin, thus making impossible one’s conversion, and consequently the remission of sins, which one considers not essential or not important for one’s life.
This is a state of spiritual ruin, because blasphemy against the Holy Spirit does not allow one to escape from one’s self-imposed imprisonment and open oneself to the divine sources of the purification of consciences and of the remission of sins.
47. The action of the Spirit of truth, which works toward salvific “convincing concerning sin,” encounters in a person in this condition an interior resistance, as it were an impenetrability of conscience, a state of mind which could be described as fixed by reason of a free choice. This is what Sacred Scripture usually calls “hardness of heart.”184
In our own time this attitude of mind and heart is perhaps reflected in the loss of the sense of sin, to which the Apostolic Exhortation Reconciliatio et Paenitentia devotes many pages.185
Pope Pius XII had already declared that “the sin of the century is the loss of the sense of sin,”“186 and this loss goes hand in hand with the “loss of the sense of God.”
In the Exhortation just mentioned we read: “In fact, God is the origin and the supreme end of man, and carries in himself a divine seed. Hence it is the reality of God that reveals and illustrates the mystery of man. It is therefore vain to hope that there will take root a sense of sin against man and against human values, if there is no sense of offense against God, namely the true sense of sin.”187
Hence the Church constantly implores from God the grace that integrity of human consciences will not be lost, that their healthy sensitivity with regard to good and evil will not be blunted. This integrity and sensitivity are profoundly linked to the intimate action of the Spirit of truth. In this light the exhortations of St. Paul assume particular eloquence: “Do not quench the Spirit”; “Do not grieve the Holy Spirit.”188 But above all the Church constantly implores with the greatest fervor that there will be no increase in the world of the sin that the Gospel calls “blasphemy against the Holy Spirit.” Rather, she prays that it will decrease in human souls-and consequently in the forms and structures of society itself-and that it will make room for that openness of conscience necessary for the saving action of the Holy Spirit. The Church prays that the dangerous sin against the Spirit will give way to a holy readiness to accept his mission as the Counselor, when he comes to “convince the world concerning sin, and righteousness and judgment.”
see from Dominum et vivificantem 46 -47
or see p 636-637
Companion to the Catechism of the Catholic Church