Taken as a whole the Bible points insistently toward the salvific role of sacrifice, and Christians have long held that this recurrent theme is a kind of prelude to the greatest sacrifice in history: The sacrifice of Christ on Calvary. Jesus' death is seen by Christians as being more than just a martyr's execution. It has for 2000 years been viewed as a substitutionary atonement for the sin of all mankind.
Our betrayal of God - our falleness - requires, in the Divine economy, that our self-imposed estrangement from Him be permanent. The divine law demands a complete divorce with no reconciliation, but Divine Love also has its demands and it was out of that love that God refused to give up on His beloved. He chose rather to do all He could to redeem mankind from the stringent requirements of the law.
His solution was to take our place, to die physically in our stead, to pay the price for our sin. Somehow, even the temporary death of an infinite God was commensurate to the eternal deaths of finite men. God's death in Christ settled a debt that otherwise could never have been paid and insured that even though we still must endure the fears and sufferings of physical death ourselves, our separation from God need no longer be forever. There is now a chance for reconciliation, both corporately and individually. Because of His death, ours is now more like a birth into a new existence, a reunion with the creator and source of all that is good in this world.
But a question arises: Was the death of Christ sufficient to guarantee that no one at all would be left out of eternal union with God? Christians have historically given several answers to this question. One answer is that this salvation from eternal death is granted only to those who repent of their sin and accept Jesus' forgiveness and own Him as their God. This pretty much limits eternal life to Christians and is a view called "exclusivism" by theologians.
Another answer to the question says that Christ's death paid the price for everyone's sin and therefore everyone will ultimately have eternal life. This view is called "universalism" since salvation is seen as extending to everyone who ever lived no matter what their life was like.
A third view, called "inclusivism," falls between the other two. It agrees with the exclusivists in that it maintains that apart from Christ's sacrifice no one would have eternal life, but it also partly agrees with the universalists in believing that God accepts into His bosom more than just those who've made a willful decision to accept Christ as their savior. It holds that salvation is a matter of the condition and attitude of one's heart toward God.
Jesus' work on the cross is the price paid to secure salvation for anyone who obtains it, but those who never heard of Jesus, or who for cultural reasons, perhaps, find it exceedingly implausible that Jesus' death was a divine gift are nevertheless not excluded from receiving it. People whose hearts are open to God, people who, indeed, may be infatuated with God, are embraced by Him even though their understanding of His redemption is inadequate or attenuated. After all, whose understanding isn't?
Theological conservatives (fundamentalists and evangelicals) tend to hold the exclusivist position, liberals (e.g. unitarians) tend to be universalists, and moderates tend to be inclusivists.
But what of those who choose not to accept Christ, whose hearts are closed to God, who would prefer that He not even exist and who would find eternity with Him to be a kind of hell? A possible answer to this question is that God compels no one to love Him. He forces no one to accept His embrace. Those who find the very idea of God repellant, who want to have nothing to do with Him, will be given their way. They will be, for as long as they wish and/or as long as they exist, separated by their own volition from the source of everything that is good. They choose for themselves a destiny devoid of the love, peace, happiness, and intellectual stimulation that flows from God.
It's a tragic choice, but God will not force us against our will to choose Him. It might be noted that if this is true then universalism must be false. People can choose not to accept heaven. Read C.S. Lewis' fanciful description of this state of mind in The Great Divorce.
Our earlier posts on Christian Belief can be found here(I), here(II), here(III), and here(IV).