Christian theologians and philosophers, like those of Judaism and Islam, believed that God is a personal, omnipotent, omniescent, infinite and good Being. Because God is personal, he is like a person, although God’s nature and essence (what God is) are transcendent and not comprehensible in this lifetime.
As God is personal, the scriptures of Christianity (the fundamental source of Christian teaching and belief) hold that God has a relationship to human beings. To be ‘right’ in this relationship, humans must obey God’s will and laws in the proper manner.
There is evident evil and suffering in the world, and there are a few possible explanations for this. One is that evil shows that God does not exist, or is finite or unable or unwilling to stop evil from occuring. Another is that God gave humans free will and allows them to exercise free will, but is not directly responsible for the evil and suffering that results from misuse of free will. Another is that humans have no free will and our fate is determined by God’s power or by some sort of necessity.
Christian theologians and other monotheistic theologians and philosophers generally choose the ‘free will’ defence to explain the outcome of evil choices of human will, including negative consequences. In Christian theology, the worst outcome of a act of will which chooses the wrong object or goal is final and eternal separation from God, and consignment to hell as a consequence. Depending on the Christian denomination and the teaching involved, the sort of sins or actions which lead to this outcome vary, but the outcome is the same.
In Catholic Christianity, ‘mortal sin’ which is not repented of before death is what leads to hell. Final impenitence, which is the final state of the damned person, is the consequence, but the outcome is not due to divine necessity but due to personal choice.
In some strands of Christian belief, such as that of Calvin and Jansenist theology, and also in some of Augustine’s theology, God separates humanity into groups (the composition of these groups is determined by inscrutable divine will) whose fate is determined by God from eternity; the doctrine of predestination. God ‘predestines’ some souls to be saved, and others to be damned. This occupied the attention of Christian theologians since St Paul, and the basic question is how to reconcile God’s absolute foreknowledge of future contingent events (which follows from his omniescence ) with the free will defence placing responsibility for evil and its consequences on humans rather than God. To some degree then, there is a question on whether free will can be reconciled with divine foreknowledge, and predestination is one solution.
The doctrine of predestination remains strong in some Christian theological circles, but the teaching seems to have been moderated a bit in recent decades.