Mark recalls Jesus speaking about the “unpardonable sin” this way:
28 “Truly, I say to you, all sins will be forgiven the children of man, and whatever blasphemies they utter, 29 but whoever blasphemes against the Holy Spirit never has forgiveness, but is guilty of an eternal sin” [Mark 3:28-29 ESV]
Is it possible for a person to commit this sin? Is there really an action terrible enough to merit this kind of condemnation? How do I know if I’ve committed this sin?
Questions swirl around this teaching of Jesus. And it’s not likely that Christians will stop wondering anytime soon. For one thing, it shows up in Matthew, and Mark, and Luke. You can’t simply pick you favorite Gospel (unless, I suppose, yours is John), and avoid it. It’s going to come up if you read your Bible. And secondly, because eternity is a long time. I know that “eternal condemnation” is a laughable (and even pitiable) idea for people who don’t follow Jesus — but to those who have seen and believed, this teaching of Jesus is sobering. Forever is forever.
So, what is it?
Context Is Key
If you don’t read this passage with the before-and-after material in mind, you’re going to misunderstand what Jesus is saying. Here’s what happens before:
 Now he was casting out a demon that was mute. When the demon had gone out, the mute man spoke, and the people marveled.  But some of them said, “He casts out demons by Beelzebul, the prince of demons,”  while others, to test him, kept seeking from him a sign from heaven.
(Luke 11:14-16 ESV)
Here’s what just happened: A group of people watch Jesus heal a man who was possessed by a demon. This group of people respond in two different ways. One group “marvels” because they’re sure that Jesus did this with God’s power and authority. The other group scoffs. They’re sure that Jesus did this with the demon’s power and authority. We see this in the next verse:
 But some of them said, “He casts out demons by Beelzebul, the prince of demons,”
(Luke 11:15 ESV)
One group says: Jesus heals with God’s power. The other says: Jesus heals with Beelzebul’s (Satan) power. Jesus’ ability to heal is understood in two different ways. One says it’s from God. The other says it’s from Satan.
Blasphemy of the Holy Spirit – In Context
Jesus answers this evaluation of his ministry by saying that 1) it’s illogical, and 2) it’s inconsistent. It’s illogical because no ruling authority attacks it’s own members. How and why would Satan cast out his own demons? And it’s inconsistent because there were many other Jewish rabbis who had done similar acts of exorcism and never experienced this kind of criticism.
It’s in this context that our “blasphemy of the Holy Spirit,” or unforgivable sin, shows up. And if you’ve followed along so far, I think you’ll begin to see why this context of healing->evaluation->differing conclusions, is so helpful.
Jesus goes on to say:
28 But if it is by the Spirit of God that I cast out demons, then the kingdom of God has come upon you.
If you want to understand what the unpardonable sin is, then you have to understand this verse. This verse is what we might call “the interpretive key.” Put this verse in the lock, turn it, and things begin to open up. If Jesus really is doing things with God’s power and authority, then the observer (us, and the original audience) must be very careful about how we evaluate what we see in Jesus. If God really is in fact empowering Jesus to do these incredible things, then to say, “he’s doing this by Satan’s power” is to misjudge him, and call God’s acts through him, “evil.”
Craig Blomberg sums it all up brilliantly in his book Jesus and the Gospels (pg 280) by saying,
“In context, blasphemy against the Holy Spirit means the persistent equation of Christ’s power with the demonic by those who refuse to believe him.”
When you take a few minutes to read the before-and-after material, this unforgivable sin becomes much clearer.
But there are still one issue I want to address: What if, at one point, you decide in a fury to yell out, “I deny the work of the Holy Spirit in Jesus”? Is there any way to repent, or have you crossed a “point of no return”?
(This is the first installment of two posts on the “unforgivable sin.” The first post answers the question, “what is it?” The second post will answer the question, “Can I repent of the unforgivable sin?”)