Are there unforgivable sins?

I strongly disagree with most of the answers given here: The answer to your question is an absolute No!

I will also cite Matthew (5:43-48):

“You have heard that it was said, ‘Love your neighbor[a] and hate your enemy.’
44 But I tell you, love your enemies and pray for those who persecute you,
45 that you may be children of your Father in heaven. He causes his sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous.
46 If you love those who love you, what reward will you get? Are not even the tax collectors doing that?
47 And if you greet only your own people, what are you doing more than others? Do not even pagans do that?
48 Be perfect, therefore, as your heavenly Father is perfect.

It is clearly written here that perfection encompasses total forgivingness. Otherwise God would not be perfect which he is - he would be like a "tax collector". So he will forgive every sin and that is the incomprehensibly great story about our Saviour Jesus Christ.

It clearly encompasses "those who persecute you" which translates even to people that hate God and Jesus (or don't believe in him) - they will be saved too, this is the overwhelmingly good message of Jesus! He also gives the example of his causing the sun to rise on the evil! There is obviously no room for interpretation here because "the evil" is explicitly addressed.

It could justly be said that people who believe that God doesn't forgive everything accuse God of not being perfect because he would only reward those that love him (= "tax collector"). They don't understand the fantastic message Jesus is giving us here!

I think Jesus had a point and it is no coincidence that he is so direct here and gives so many clear examples.

The only unforgivable sin is blasphemy against the holy spirit. Hebrews 6 and 10 are both referring to Jews who had became Christians but were now considering renouncing Christ because of fear of persecution and thought they could go back to animal sacrifices to cover their sin in the future. He is not talking about unforgivable sins, rather that having being enlightened to the true payment for sin there is now no way back. In short he is saying that if you are enlightened about true forgiveness and then choose to reject that : there is now nowhere else to go; because animal sacrifices were only a foreshadow of the Christ. It is not saying that your sin is unforgivable but rather that having rejected the true forgiveness there is no other (and never was). People tend to confuse this with turning your back on god but that's not what it's about at all. It would fly in the face of the passages about the prodigal son and the teaching about "forgive your brother seven times seventy seven" ( so clearly god will always forgive us if we repent, no matter what the circumstances ). Blaspheming the HP is clearly in a class of it's own.

Let us look at Hebrews 6:4-8.

“It is impossible for those who have once been enlightened, who have tasted the heavenly gift, who have shared in the Holy Spirit, who have tasted the goodness of the word of God and the powers of the coming age and who have fallen away, to be brought back to repentance. To their loss they are crucifying the Son of God all over again and subjecting him to public disgrace. Land that drinks in the rain often falling on it and that produces a crop useful to those for whom it is farmed receives the blessing of God. But land that produces thorns and thistles is worthless and is in danger of being cursed. In the end it will be burned. Even though we speak like this, dear friends, we are convinced of better things in your case — the things that have to do with salvation.”

In short, for those people who have fallen away from God after all the mercy and forgiveness they have been given is simply trampling Son of god under their feet. There is similar passage in Hebrews 10:26-29.

26 If we deliberately keep on sinning after we have received the knowledge of the truth, no sacrifice for sins is left, 27 but only a fearful expectation of judgment and of raging fire that will consume the enemies of God. 28 Anyone who rejected the law of Moses died without mercy on the testimony of two or three witnesses. 29 How much more severely do you think someone deserves to be punished who has trampled the Son of God underfoot, who has treated as an unholy thing the blood of the covenant that sanctified them, and who has insulted the Spirit of grace?

As stated here, falling out of God after having knowledge of consequences is as same as insulting Spirit of Grace.

It is important to note that the default condition of the world is that of being under condemnation, according to John 3:18:

Whoever believes in him is not condemned, but whoever does not believe is condemned already, because he has not believed in the name of the only Son of God. John 3:18

All men have sinned and fallen short of the glory of God (Romans 3:23) and are already dead in their trespasses and sins (Colossians 2:13).

Consequently, the question is not so much if there is there any unforgivable sin that a Christian can commit that will result in his losing salvation. Rather, it is what an unbeliever does that precludes him from being made alive, forgiven, and given eternal life.

The answer is his failure to recognize Jesus as the Messiah and trust in His substitionary atonement on the Cross and His resurrection from the dead. The sin of the Pharisees was, when seeing the evidence of the Messiahship and Deity of Jesus, they rejected it.

We must understand that it is the Holy Spirit who "convicts the world of sin and righteousness and judgment" to draw them to faith. So, it seems that people can blaspheme the Father and the Son and be forgiven, yet blaspheming the Holy Spirit may result in the Holy Spirit ceasing to draw the person to faith in Christ, rendering that person unforgivable.

Forgiveness comes through faith in Christ, and faith in Christ comes at the beckoning of the Holy Spirit. So, once again, the blaspheming of the Holy Spirit may result in the cessation of His drawing of a person to faith in Christ.

And when he comes, he will convict the world concerning sin and righteousness and judgment: concerning sin, because they do not believe in me; concerning righteousness, because I go to the Father, and you will see me no longer; concerning judgment, because the ruler of this world is judged. John 16:8-11

So, yes, there is an unforgivable sin, but this isn't something a Christian can commit. It's something an unbeliever can commit by quenching the One who draws him to faith in Christ, through which forgiveness is received.

In the gospels Jesus speaks, as your question points out, of the unforgivable sin of blasphemy against the Holy Spirit. Indeed it's true that blaspheming the Spirit of God is a grave sin. It's important to keep in mind that he was speaking not to his disciples or to the crowds following him, but to the Pharisees who accused him saying "It is only by Beelzebul, the ruler of the demons, that this fellow casts out the demons." Those Pharisees did not say what they said by carelessness or momentary anger. They said it intentionally and deliberately, in order to entrap Jesus. And his response ("unforgivable sin") was an explanation of the spiritual consequences of their actions. I think he was inviting them to repent. But what do I know?

Sisters and brothers, for pastoral reasons I urge you to be very VERY careful with speech about this unforgivable sin. There are a surprising number of people in this broken world of ours who have become convinced that they have committed this sin and are beyond redemption.

The ones I have spoken to are seriously seeking some kind of reconciliation, but have become convinced they're not worth it. Some are struggling with intrusive thoughts of personal unworthiness, and others are struggling to repent of past angry thoughts or words. Not one of these people seeking redemption from God can possibly be guilty of this sin of blasphemy against the Spirit: it is that same Spirit that inhabits their hearts and turns them to seek God. Jesus did not turn away ANYONE who sincerely sought healing or repentance.

So, let's you and I leave all judgement about this sin to God, OK? Please? For the life of the world?