This question even haunted me back in Bible College. Think about a child born in a Muslim household. The child has been brainwashed from birth into the mysticisms and mythologies of Islam and will grow to despise Jews and the West. At some point he is recruited to wear some TNT around his midsection and his last act will be the murder of about a dozen Jewish and Western civilians. Christianity will dicate that this soul would end up in hell but does that make sense? Seriously, did the child ever have a chance or a real choice in the matter? The answer, despite Christian rationalization, is a resounding NO!
What about Free Will?
It is a testament to the artificiality of this philosophy that only those who believe in some Just, Almighty God subscribe to it. You see, if we accept the fact that someone's behavior is simply the predictable result of his genetics and environment then we cannot possibly believe that a just god would send that person's soul to hell. Enter the artificial theory of "free will". People can choose to be evil or be good and therefore God simply punishes for the action of this "free will". All it takes to disprove this bizarre theory is the following question "Do believe in teaching children morality and disciplining them?" If you said yes to this question than you can't believe in "free will". Let's say we have two children; one raised by you and one who grows up without parents. According to "free will" both children have the same chance of doing what's right or wrong. In reality, however, your child will certainly act differently from the other child specifically because of how you raised it. Neither child is responsible for how it is raised but your child would have a MUCH better chance of being good and going to heaven than the other child. How is that fair to the child without parents?
If We're Not Responsible For Our Behavior Than Why Punish?
Christians are so used to the concept of sin and punishment that they shocked by the realization that behavior is simply the result of environment and genetics. "Why punish people who are not responsible for what they do?" Simply put - we don't punish people because we're making some sort of higher, eschatological moral judgement on their culpability; we punish to adjust behavior. We punish criminals, pets, children in order to adjust behavior. If someone is caught shoplifting and is not punished then he has no incentive not to do it again. If, however, he is punished then a new set of variables is pushed into his decision making process and he is less likely to do it again. The same is true when we punish children or pets; we're adjusting behavior - it's like reprogramming a computer.
Eternal Punishment
Which brings us to the pointless sadism of 'Eternal Punishment'. We, as humans, punish in order to adjust behavior. Punishing a soul for eternity is an oxymoron of a statement since the person has no opportunity to learn from the punishment. Eternal punishment, unlike earthly punishment, does nothing for the person being punished and is, therefore, just pointless sadism.
The rest of this is just clarification of the earlier points but I've included these quesions here because these're real questions asked about this subject.
If we don't have free will, then good and evil can't
make sense.
Good/Evil, Right/Wrong, Holy/Unholy do not make sense in a larger eschatalogical way. It doesn't make sense that any god would condemn a Muslim child of Al Qadim terrorists to hell for behaving in a very predictable way. In the real world, however, good and bad make perfect sense. If your child does something good you probably reward him, tell him that he is good for performing a good deed and give him a cookie - this reinforces good behavior (environment). You see, good and bad are just words we use when we want to adjust behavior. We WANT people to act good (in a healthy fashion towards themselves and their society) so we praise good behavior to influence people to act that way or punish bad behavior so that we can influence people NOT to act in an unhealthy way.
You say we are not responsible for our deeds.
Our behavior is predictable but we are responsible for our behavior. You ARE your genetics and environment; you are NOT some "free will" sitting above your hormones, experiences, chemical reactions and societal influences. Although your decisions are pretty much predictable you are still responsible for them and will be punished or praised for them.
So we can't be praised or blamed for good or evil?
If you don't praise someone for good or punish for bad then you're not providing incentive for good behavior or disincentive for poor behavior. Besides, aren't people praised all the time for attributes that are just part of their genetic package? Praise is common for intelligence, height, beautiful eyes, long legs... even though the person is clearly not responsible for these attributes - he/she will gladly accept the compliment.