Paul says the blindness in part has happened until the fullness of the Gentiles comes in.
Exactly.
The word until means up to or as far as.
Yep.
The condition of partial blindness happens up to or as far as the fullness of the Gentiles. The partial blindness doesn’t happen past that point.
Agree.
How can the mystery of Romans 11:25 be talking about partial blindness as a fraction of the people being spiritually blind and a fraction of the people not being spiritually blind?
How can it not? Are you looking for context? Please read this:
Romans 11:5 Even so then
at this present time also there is a remnant according to the election of grace. 6 And if by grace, then is it no more of works: otherwise grace is no more grace. But if it be of works, then it is no more grace: otherwise work is no more work. 7 What then?
Israel hath not obtained that which he seeketh for; but the election hath obtained it, and the rest were blinded.
So, the "remnant according to the election of grace" was not blinded "and the rest were blinded". So, it's obvious to me that Israel being blinded in part refers to the fact that some, but not all, of the Israelites were blinded.
A mystery is something hidden in the Old Testament and revealed in the New Testament.
Not necessarily. It can be, such as in the case of the fact that Gentile believers are fellowheirs with Israelite believers of God's promises (Eph 3:1-6), but that doesn't have to be the case.
Are you suggesting that it was not understood that some Israelites weren’t saved until Paul revealed this mystery to us?
LOL. Of course not. The mystery is simply that the partial blindness status of Israel would continue until the fullness of the Gentiles comes in, which was not previously revealed until Paul revealed it.
Because it was meant to provoke those who kept the burden of the old covenant into an understanding that under the new covenant those burdens were unnecessary.
After the cross the burden of the old covenant was still being observed by the Jews, while the Gentiles had a different burden, this seemed good to the Holy Spirit in Acts 15:28.
No, it wasn't. Just read Galatians 3 to see if God still wanted people to keep the old covenant law. He did not. But, I'm not going to argue with you about this again. Let's stay on topic with Romans 11. I don't believe what you're talking about has anything to do with Romans 11.
In Hebrews 8:13 the old covenant was ready to vanish away
Not the old covenant itself. It was already obsolete. You either accept that it was obsolete at that point or not. What's your decision? If you agree with the verse saying that it was obsolete at that point, then you need to figure out what the difference is between it being obsolete and it vanishing away. It seems that you do not differentiate between those things for some reason.
and in 2 Corinthians 3:14 it is the reading of the old covenant that is the vail on their hearts. Once that old covenant vanished that vail vanished.
Someone today can believe in the old covenant and reject the new covenant but that is not the vail, the old covenant has vanished. In the first century someone could have the Holy Spirit and hear the reading of the old covenant and conclude it was good, that temporary situation ended when the old covenant vanished.
Let’s face it, no church today asks if you’re a Jew or Gentile in order to determine which burden should be placed on that individual. The temporary blindness on Israel has ended, there is no difference between ethnic Israel and Gentile since that old covenant vanished.
I think you are taking Romans 11 completely out of context and it has nothing to do with what you're talking about. How did the fullness of the Gentiles already come in long ago? That makes no sense. What does "the fullness of the Gentiles" mean to you? To me, it's talking about the point at which every Gentile who will be saved has been saved. The process God began long ago of the Gentiles provoking Israelites to jealousy and leading them to salvation will continue until the last Gentile has been saved.