Q: Is the sin against the Holy Spirit simply the sin of unbelief?”
A: No, there is an important distinction. The sin against the Holy Spirit is described as “unforgivable,” due to its very nature of involving blasphemies against the Holy Spirit and thereby prohibiting the Spirit from ever working repentance in the heart (Matt. 12:31, 32; Mark 3:28, 29; Luke 12:10; Heb. 6:4-6; and Heb. 10:26, 29). It is a callous rejection of the truth on the part of one who would already have known and embraced the truth, and it also must include voluntary and atrocious verbal assaults against the Spirit. The sin of unbelief–by its definition–is a sin of which there can be repentance, even when we are discussing those who once embraced the truth but now do not (see Rom. 11:23). The end results for a person who persists in unbelief and for a person who commits the sin against the Holy Spirit are, of course, the same: eternal damnation. Yet, this biblical difference should be upheld: While unbelief is naturally included in the unpardonable sin, more is exhibited here, such as cursing the very name of the Spirit who alone enacts conversion.
Since we are unable to tell when an individual has committed this sin, we ought never charge anyone with it. Warnings are appropriate, nevertheless, for those who are around the truth but repeatedly turn a deaf ear. If one is afraid that he or she has committed this sin, that person should rest assured that it definitely has not been committed. Were it the case of having done so, one wouldn’t even be the slightest bit concerned about the possibility of the sin being committed. “It is God who works in you to will and to act according to His good purpose,” (Phil. 2: 13.)