Christians predeterminism, as I understand it from those that teach it, is a kind of no-choice-about-it faith and salvation. God has already decided who will believe Him unto salvation, and who will not.
If it were a simple matter of foreknowing who would and would not, then that is just the omniscience of God. However, I have found that the teaching of predeterminism includes God creating men and women differently. It suggests that God is a respecter of persons. He actually creates and makes some in His image with power to believe and willingness to obey Him, while others are not, or are created of a lesser image of God. It's like God picking and choosing the winners of life's lottery, when He creates us. Those who are determined by God to believe and obey, shall do so, because He creates them that way, and those who are not determined to do so, shall not, because He purposely creates them another lesser way.
I find this most offensive, and an accusation against the God that is love and would have all men to be saved by faith in His Son.
The main verse of the Bible they use most is John 5:16, Ye have not chosen me, but I have chosen you, and ordained you, that ye should go and bring forth fruit, and that your fruit should remain: that whatsoever ye shall ask of the Father in my name, he may give it you.
They use this to say we have no individual choice in the matter of believing and being saved, but each person is fated one way or the other. It's the Christian version of pagan divine fatalism, that Jesus Christ came to destroy.
In the verse, Jesus is not saying we have not chosen to believe He is the Christ, but rather we have not chosen Him to be the Christ of God. We must understand old paganism to understand what He was dispelling among His disciples. Pagans believed they could choose from among many gods, the one they most wanted to please and receive blessing and protection from. They could make one god of many into their 'patron god'. Whole cities would do so, such as Ephesus of Diana and Egyptian Thebes of Amun. Catholics have a version of it with patron saints.
What Jesus is telling us, is to not thinks as the pagans think, and suppose we are choosing who is the true Christ and Lord for ourselves, from among many gods, christs and lords. We do not choose Him to ourselves as the best candidate for God's Christ. We are not favoring Him with our own form of election, of who is the best of the gods for us.
When Jesus therefore perceived that they would come and take him by force, to make him a king, he departed again into a mountain himself alone.
The Jews were trying to do the same thing, by trying to choose Jesus for themselves to be their very own personal king. Jesus would have none of it. Jesus is telling us that we do not choose Him from among other christs and gods to be our King and Lord, but that we are either to believe He is the one and only Christ of God, or not. And so, he chooses them that do believe from the heart, that He is indeed the only true Christ and Lord and Savior for men.
And so, it's not that we have no choice nor say in the matter. God neither creates us different from others to become saved believers, nor does Jesus choose us 'randomly' out of crowd to be His special people. The truth is that there is only one true choice to make: we either choose to believe He is the true Christ of God sent for our redemption by faith, or we choose not to.
We have not chosen and 'elected' Him to be Christ, but we choose to believe He is indeed Christ. And so, He chooses to elect us to be His people by His faith recieved and kept in our hearts.
Keeping His faith is always a matter of choice, because all that hear His word do receive the faith instantly into the heart, but not all keep His faith in the heart. And these are they by the way side, where the word is sown; but when they have heard, Satan cometh immediately, and taketh away the word that was sown in their hearts.
All choose to have Jesus' faith sown in their hearts by hearing the word alone, but all hearers do not choose to do the word and keep His faith unto salvation and everlasting life. All choose to be hearers of the world, by hearing it, but only the few choose to be doers of the word by keeping it in their hearts.
If Christian predeterminism were true, and God does in fact make some people with power of will to believe and obey Him, and some He makes a lesser version of His image without such power, and then Jesus chooses us accordingly at some point in our lives, then the exhortation to keep and continue in the faith is a redundant waste of time. It would be like telling birds to keep flying in the air, and not stop and drop to the ground, or coaxing cars to continue burning fuel from a full gas tank.
Christian predeterminism makes no practical sense and is an abhorrent teaching, that God purposely and wilfully makes some men to do good, and others to do evil. That is what James calls a false accusation against God. Let no man say when he is tempted, I am tempted of God: for God cannot be tempted with evil, neither tempteth he any man.