"It should not be overlooked that we tend to regard predestination as a part of a philosophical theory. For us it is the answer to the question, 'Are all things determined or not?' For Paul it is the answer to quite another question, 'How much of our salvation is due to God?' It is part of man's make-up that he likes to think that he earns his salvation. When he sees that the cross rules out the way of human merit and that he is saved by grace, by God's free gift, he tries to salvage something from the wreck. He thinks that at any rate he deserves some credit. He made the right decision. He decided to be a Christian. He chose God. The doctrine of predestination takes this last prop from under him. He could not decide this, left to himself. The reason he is a believer is not that he chose God but that God chose him. Predestination is the assurance that all of our salvation, from the very beginning to the end, is of God. We ought never to think of it other than in relation to salvation. That is where Paul sets it. It assures me that my salvation is no improvised affair, brought into being by a more or less fortuitous decision of my own. I am saved because none less than God willed it and predestined me before all the ages. Nothing at all can give the believer assurance like this great truth."
--Leon Morris, The Cross in the New Testament, p.215