There is no sin too great to be forgiven provided one sincerely repents of it. Christ really referred to evil dispositions of soul which are so hardened that one will lack the will to repent. Blasphemy against the Holy Spirit is not blasphemy as commonly understood, but a determined resistance to the very grace of the Holy Spirit which is meant to save us. Thus the Pharisees who saw the miracles of Christ could not deny them to be miracles; yet rather than yield to the grace being offered them, they said that Christ wrought them with the help of the devil, and not by God. A man who rejects the very means God adopts to convert him is little likely to make good use of other graces offered by God, and Our Lord warns us very strongly to beware of sinning against the light, since it seldom ends in repentance. Yet even such a man with the help of special grace could repent of his bad dispositions and thus be converted and forgiven. Any unforgivableness, therefore, is on account of a man’s bad dispositions, not on account of the nature of the sin. There is no absolutely unforgivable sin such as cannot be forgiven even though a man repents.
Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty