What is blasphemy against the Holy Ghost?

Matthew 12:31 and 12:32 is repeated in Mark 3:29. “But he that shall blaspheme against the Holy Ghost hath never forgiveness, but is in danger of eternal damnation.”
Both essentially say that blasphemy against the Holy Ghost will never be forgiven as spoken by Christ himself. This seems unusually sever and contradicts the concept that with Christ all sins are forgivable. Does this make sense as written? If so, please describe and give an example of blasphemy.

Thank you

Catechism of the Catholic Church:

**1864 **“Therefore I tell you, every sin and blasphemy will be forgiven men, but the blasphemy against the Spirit will not be forgiven.” There are no limits to the mercy of God, but anyone who deliberately refuses to accept his mercy by repenting, rejects the forgiveness of his sins and the salvation offered by the Holy Spirit. Such hardness of heart can lead to final impenitence and eternal loss.

Blasphemy against the Holy Spirit means refusing the forgiveness of God. God does not force Himself upon us, if we do not wish to be with Him then He will permit us to be separated from Him. God offers us His forgiveness always but if we refuse it then we do not receive it.

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