This question touches on so many Biblical subjects, I can’t possibly go into depth and provide in depth answers on all of them. Otherwise each point would be as long as this answer on its own. So if you’re a Calvinist reading this, try not to get offended. Keep believing what you want. And there will be subject like demons and sons of God that are controversial, please check out other questions about these subjects I’m trying to answer only the question asked
If you will let the Bible speak for itself then you will get an answer. But if you come to the Bible with an already preconceived interpretation and try to make it fit, it’s going to get very difficult to understand the passages.
having been predetermined
That is out of context but based on your comments that you want a reformed view, you are talking about Calvinism.
First predestination means to set a destination in advance. The destination set in advance commences according to Scripture at the point of salvation and not before Creation.
This all happens, key words, IN HIM
“even as he chose us in him before the foundation of the world, that we should be holy and blameless before him. In love”
No human was predestined IN HIM, in Christ prior to Creation, only Christ was predestined prior to Creation. Upon entering Christ we too partake of everything due Him, if we remain IN HIM.
We were all IN ADAM
“Just as we have borne the image of the man of dust, we shall also bear the image of the man of heaven. I tell you this, brothers: flesh and blood cannot inherit the kingdom of God, nor does the perishable inherit the imperishable.”
1 Corinthians 15:49-50
And we were all predestined in Adam for life but Adam failed
“For as in Adam all die, so also in Christ shall all be made alive.”
1 Corinthians 15:22
Notice it’s a future tense with Christ. That’s what we are predestined once we get into Christ, imperishable bodies and life.
But fact is we are all in Adam
“For as by a man came death, by a man has come also the resurrection of the dead.”
1 Corinthians 15:21
If we were not all in Adam then we would not all be subject to death, only Adam would have been. But since we are subject to death, it attests that we were in his loins.
No where in Scripture will you find names being added to the Book of Life after Creation
What you will find is that names are all added prior to Creation.
“and all who dwell on earth will worship it, everyone whose name has not been written before the foundation of the world in the book of life of the Lamb who was slain.”
In this passage we find earth dwellers who were never written in the book of life, ever. If you assume they are human you will have to then make something up about predetermined humans for hell or heaven.
These are those who came as a result of the sons of God (most will understand angels) in Genesis 6 taking human women as wives and the hybrid children having a nephesh (soul) that did not and could not have come from God. When these hybrid human/angels died their physical bodies disintegrated but they continued to roam the earth. They being spirits needed bodies to manifest. They are also known as demons. They are the earth dwellers and they will give their obedience to the beast.
Humans are all written in the book of life. It’s a registry of names.
It was always God’s intention that every human live. We were all written in that book. But we can opt out. That’s where the erasing comes into the picture.
Adam failed! As a result we were all condemned. But instead of erasing everyone out, God allowed every person on an individual level to chose to remain or be blotted out. That’s God’s grace and goodness. So in the first Adam we lost it all. In the second and final Adam we regain it all back and our names can stay in the book of life.
In Christ we have been predestined to glory, which is our glorified bodies. We haven’t got them yet but if we remain in him we will.
In order to remain in the book, you had to first have been in it.
It’s clear that the only time the Bible mentions names being written in, is before Creation
To stay in you must conquer by remaining IN HIM
But if you are outside of Him, He will erase you out of the book. And the only reason He erases anyone is because they reject Him. Because The first Adam failed.
“The one who conquers will be clothed thus in white garments, and I will never blot his name out of the book of life. I will confess his name before my Father and before his angels.”