Expat: I found another WT article for you on the subject...a QFR in the 1969 Watchtower, which answers it more in the tone typical of that time period..not quite as vague as today's methods.
*** w69 8/15 511-2 Questions from Readers ***
• What is the unforgivable sin?—E. M., U.S.A.
The type of sin mentioned in the Bible as being unforgivable is not simply a category such as stealing, lying or sexual immorality. These things are serious, however, and may involve unforgivable sin. (Rev. 21:8) But the unforgivable sin is deliberate sin against the manifest operation of God’s spirit. It springs from a heart that is thoroughly and forever alienated from God.
Jewish religious leaders who came to Galilee to see and hear Jesus Christ on one occasion had already taken counsel as to how they might destroy him. (Matt. 12:14) In Galilee they saw Jesus cure a man who was unable to speak, was blind and demon-possessed. Instead of admitting the obvious fact, that Jesus was performing miracles by means of God’s holy spirit, the Pharisees maliciously accused him of doing it by means of the power of Satan. After showing how wrong they were, Jesus said:
“Every sort of sin and blasphemy will be forgiven men, but the blasphemy against the spirit will not be forgiven. For example, whoever speaks a word against the Son of man, it will be forgiven him; but whoever speaks against the holy spirit, it will not be forgiven him, no, not in the present system of things nor in that to come.”—Matt. 12:31, 32; Mark 3:28, 29; Luke 12:10.
With these religious leaders it was not just a case of failing to be convinced by Christ’s teachings and works. The people of Chorazin and Bethsaida had been so preoccupied with their way of life that they did not accept Jesus and repent; yet they evidently will benefit from God’s mercy and have a resurrection and a future opportunity to learn the way of righteousness. (Matt. 11:20-24) Nor with the Pharisees was it a matter of blaspheming and opposing true worshipers because of ignorance of God’s will. Saul of Tarsus had been such a man, but he was shown mercy and forgiven. (1 Tim. 1:13-16) Rather, these religious leaders were rotten in their hearts right to their core, and Jesus knew it. Unlike the common people, they had a considerable knowledge of God’s Word. Now they had seen an evident demonstration of God’s spirit. Nevertheless, they completely rejected what was accomplished by Jehovah’s spirit and blasphemously credited Jesus’ miracles to Satan’s power. How bad could one get?
Was their sin serious? Jesus, “knowing their thoughts,” realized that they were deliberately—with their eyes wide open to the facts—sinning against knowledge of the operation of the holy spirit. He indicated that they were “guilty of everlasting sin.” (Matt. 12:25; Mark 3:29) Because of the context of those words, and in view of the fact that Jesus later said that many religious leaders of that time were headed for eternal destruction in Gehenna, it seems that they had committed the unforgivable sin. (Matt. 23:15, 33) Their sin was unforgivable, not because Jehovah is not a forgiving God, but because they were past repentance and beyond being retrieved. Their sin left them in total infidelity as to the real worship of Jehovah. Even in the system of things to come, one guilty of such sin could not be forgiven.
Could one sin against the holy spirit today, and thus be beyond forgiveness? Yes, that is possible. A person could become so hopelessly corrupt in mind and heart as to carry sin to the point of sinning against the spirit. And one need not be a spirit-anointed Christian to do so. Remember that those Pharisees were not anointed Christians and yet they committed unforgivable sin.
How would one know if the unforgivable sin had been committed?
This type of sin is related to what we read in Hebrews 10:26: “If we practice sin willfully after having received the accurate knowledge of the truth, there is no longer any sacrifice for sins left.” So there is a deliberateness or willfulness about this kind of sin. One callously sins, fully aware of the fact that he is going directly contrary to the operation of God’s spirit and His righteous laws. Furthermore, we all are sinful and need Christ’s ransom sacrifice to obtain forgiveness. But “there is no longer any sacrifice for sins left” for one who knows that and “who has trampled upon the Son of God and who has esteemed as of ordinary value the blood” he shed. That one “has outraged the spirit of undeserved kindness with contempt.” (Heb. 10:29) He will never repent and humbly seek God’s forgiveness for his sin and rejection of Christ’s ransom. He is beyond repentance.
But one important point needs to be remembered: In Jesus’ case, he knew the innermost thoughts and heart condition of the Jews and could thus be certain that they had sinned against the holy spirit. Imperfect humans today cannot read hearts as can Jehovah and Jesus, so we cannot determine when someone has carried sin to the point of having sinned against the spirit. (Matt. 12:25; Heb. 4:13) That is for God to determine.
Even the fact that a person has been disfellowshiped from the Christian congregation does not necessarily mean that he has committed the unforgivable sin. He may later repent. In the early Corinthian congregation an anointed Christian had to be disfellowshiped because of his immorality and lack of evidence of repentance. Yet, apparently, that man was later reinstated into the congregation, showing that he had not sinned against the holy spirit.—1 Cor. 5:1-5; 2 Cor. 2:6-8.
Nevertheless, the mere fact that it is possible to sin against the holy spirit should put us on the alert. Being imperfect creatures, we unconsciously sin daily. If one is cut to the heart and truly repentant over his sins, then that is evidence that he has not committed the unforgivable sin. How important it is, then, to maintain a humble spirit, admitting our errors and seeking God’s forgiveness. (1 John 1:9; Mic. 7:18) And recognizing that eternal destruction will be the lot of those who are “guilty of everlasting sin,” the sin against the holy spirit, we should strive to avoid making sin a habit or denying the evident operation of God’s spirit.
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Had Enough
"Never doubt that a small group of citizens can change the world.
Indeed, it is the only thing that ever has."...Margaret Mead