Many Christians believe that when a person dies, they go to either heaven or hell. Catholics believe in purgatory, but most Protestants seem to not believe in this doctrine. Furthermore, the vast majority of Protestant Christians claim that salvation comes about through having the right belief in Jesus - who he was and a theological understanding of what he did.
This doctrine of eternal consequences without the ability to get purified in purgatory never really made logical sense to me for a number of reasons, including the contradiction between Old Testament righteous people seeming to have a good afterlife without knowing about Jesus, and slippery-slope questions about children, mentally handicapped and others who simply never heard the gospel but were more or less good people. I have encountered at least some answers to these objections, although they seemed logically incoherent to me. However, I have not heard any answers at all to the following:
Let's suppose that the Christian dogma of heaven and hell is correct. That would mean that the ultimate moral consequences are determined by God. If a person cannot bring themselves to believe in "Mere Christianity" -- because, for example, every time they try to examine the evidence for/against Christianity it leads them to the conclusion that this is a man made legend and nothing really supernatural occurred -- what incentive or reason does this person have to behave morally at all? According to Protestant Christianity, no matter how good an unbeliever behaves, even the kindest old lady gets the same exact fate as Hitler and Pol Pot. Isn't this a reductio ad absurdum, showing that the heaven/hell doctrine provides for no moral incentives for unbelievers to act good without Christian belief?