Lest you be wise in your own sight, I want you to understand this mystery, brothers: a partial hardening has come upon Israel, until the fullness of the Gentiles has come in. And in this way all Israel will be saved, as it is written, "The Deliverer will come from Zion, he will banish ungodliness from Jacob; and this will be my covenant wtih them when I take away their sins."
As regards the gospel, they are enemies of God for your sake. But as regards election, they are beloved for the sake of their forefathers. For the gifts and the calling of God are irrevocable.
For just as you were at one time disobedient to God but now have received mercy because of their disobedience, so they too have now been disobedient in order that by the mercy show to you they also may now receive mercy. For God has consigned all to disobedience, that he may have mercy on all.
To which Paul responds:
Theology is important. A proper understanding of God's character and ways, and man's condition, are vital to salvation. But it is arrogant to think that any school of theology can fully grasp and understand how God will accomplish his purposes. This passage in Romans 11, in relation to the destiny of Israel, is beyond our ability to grasp and understand. And Paul's response to this is simply to praise God for his riches and wisdom, and inscrutible nature.
Oh, the depth of the riches and wisdom and knowledge of God! How unsearchable are his judgments and how inscrutible his ways!