There are generally believed to be 6 sins that concern blaspheming the Holy Spirit: despair, presumption, impenitence or a fixed determination not to repent, obstinacy [in sin], resisting the known truth, and envy of another’s spiritual welfare.
If one does none of these things one’s grave sins are quite forgivable if repenting and confessing them before they die.
But what is absolutely certain is that final impenitence is absolute. God cannot pardon where there is no repentance, and the moment of death is the instant after which mortal sin can not be remitted. One dieing impenetent in grave sin has thus blasphemed the Holy Spirit by ignoring His incessant call to repent over the entirety of one’s life.
More Here:
Holy Spirit
A few descriptions of some of the sins that blaspheme the Holy Spirit:
Despair:
Is the voluntary and complete abandonment of all hope of saving one’s soul and of having the means required for that end. It is not a passive state of mind: on the contrary it involves a positive act of the will by which a person deliberately gives over any expectation of ever reaching eternal life. There is presupposed an intervention of the intellect in virtue of which one comes to decide definitely that salvation is impossible. This last is motived by the persuasion either that the individual’s sins are too great to be forgiven or that it is too hard for human nature to cooperate with the grace of God or that Almighty God is unwilling to aid the weakness or pardon the offenses of his creatures, etc.
It is obvious that a mere anxiety, no matter how acute, as to the hereafter is not to be identified with despair.
Presumption:
It may be defined as the condition of a soul which, because of a badly regulated reliance on God’s mercy and power, hopes for salvation without doing anything to deserve it, or for pardon of his sins without repenting of them. There are generally believed to be 5 ways in which one may be guilty of presumption.
- By hoping to obtain by one’s natural powers, unaided, what is definitely supernatural, viz. eternal bliss or the recovery of God’s friendship after grievous sin (this would involve a Pelagian frame of mind);
- A person might look to have his sins forgiven without adequate penance (this, likewise, if it were based on a seriously entertained conviction, would seem to carry with it the taint of heresy);
- A man might expect some special assistance from Almighty God for the perpetration of crime (this would be blasphemous as well as presumptuous);
- One might aspire to certain extraordinary supernatural excellencies, but without any conformity to the determinations of God’s providence. Thus one might aspire to equal in blessedness the Mother of God;
- Finally, there is the transgression of those who, whilst they continue to lead a life of sin, are as confident of a happy issue as if they had not lost their baptismal innocence.
Note: There are some fundamentalist Protestants who I believe as a matter of their doctrine are in real danger of falling under #5 in their presumption that they are free to sin (as if an expression of faith) once they think themselves “saved” no matter how objectively evil their deeds. However it may be possible that Invincible Ignorance can mitigate this.
James