If you don't mind, you raise some interesting thoughts and questions and I would like to respond to them myself.
Romans 8:33
Admittedly, the verse by itself doesn't necessitate endurance or permanence. But it resides in a context where that is the overall concept. Think of it this way: all of reality is like a house: physical things are on the bottom floor, whereas spiritual things are on the top floor. Humans, animals, planets, stars, trees, mountains, chemistry, physics, and history are all on the bottom floor. Angels, demons, Satan, and heaven are on the top floor. The entire house represents everything that is real. But nothing in the house, whether it is on the top floor or the bottom floor, is permanent. Everything is transitory.
God exists outside the house to the extent that he is self-existent and cannot "go out of existence." Paul argues that if God, who exists outside of time, space, and circumstances, justifies someone, then nothing in all of our reality can thwart his effort or will. Nothing in this reality can defeat God's will for us. This would include our will since we exist inside this reality. But Let's put that aside for now and assume that my will can still dictate my fate.
Paul argues for permanence and endurance earlier in the chapter. For the sake of his argument, Paul narrows the focus to "those who are in Christ Jesus." When Paul makes assertions about those “in Christ” in Romans 8, he is indeed speaking in a way that is categorically true, but with a very specific meaning of “categorical.” When Paul says stuff like:
- “There is now no condemnation for those in Christ Jesus”
- “The Spirit of God dwells in you”
- “You are sons and heirs”
- “Nothing can separate us from the love of God in Christ Jesus”
- how believers feel,
- how they perform,
- or how they perceive themselves.
Romans 8:28-30
Here, Paul draws a straight, unbroken line between being foreknown and glorified, affirming his belief that all those "in Christ", without exception, will experience eternal life in the coming age.
The term "foreknown" has the same meaning as "to know" in the covenant sense. Those who were in covenant with Christ will not fail to be glorified.
God preordains who will be saved and who will be judged.
You said it yourself. We are saved according to God's advance plan / divine purpose.
Some are critical of Calvinism, accusing it of being fatalistic. That is the weakness of Calvinism and a fair critique. Fatalism says that our fate is not determined by our free will choices and so it doesn't matter what we do. In the end it is always the same.
The missing piece of the foreordination picture is the idea that God not only foreordains people he foreordains their personal stories. When people talk about foreordination, they usually imagine God determining who will be saved. But Scripture’s vision is far richer and more personal. God does not merely foreordain destinations; He foreordains narratives. In other words: God does not simply foreordain that you will be His. He foreordains how you will become His.
This is the difference between a bare decree and a crafted life.
Fatalism says:
“The end is fixed, and nothing you do matters.”
Biblical predestination says something entirely different:
?The end is fixed because God is writing a story in which your actions, choices, prayers, and faith genuinely matter.”
Fatalism erases agency. Predestination establishes agency by giving it a place in a divinely crafted narrative.
This is the crucial distinction.
