Romans 11:1 meaning

Throughout Romans, Paul has been responding to slanderous charges made by competing Jewish "authorities." Their arguments were meant to set aside Paul's ministry, and their first charges were meant to portray his teaching as crazy (Romans 3:8). These authorities argued that since Paul teaches that the Jewish Law has now been set aside, then we ought to sin all we want to. The competing "authorities" argue that Paul is teaching that by sinning profusely, we are doing God a favor by expanding His grace even more. 

Paul has already defeated this slander (Romans 6:1). He demonstrated that although it is true that God's grace abounds beyond any amount of sin (Romans 5:20), it is crazy for us to sin because of the severe adverse consequences associated with sinning. Paul started his letter by showing the progressive self-destruction sin wreaks upon those who follow in its steps, progressing from lust, to addiction, to loss of mental health (Romans 1:24, 26, 28). 

Paul also asserted that Jesus has abolished the Law, and has given us the power of the Spirit to actually experience a righteous life through living by faith. But here, it seems Paul now answers a follow-up argument against his teaching, along the lines of "If the Law has been set aside, if we're no longer under the Law, then that means Israel has been set aside. And Israel no longer has a purpose in God's plan."

"So," the competing Jewish authorities might conclude, "we've got all this history leading up to this point in God's dealing with His people (the Jewish people), and He just suddenly shoves them aside? See, this is another reason Paul's teaching, which emphasizes grace and faith, is false." Paul now answers this allegation, that God has rejected His people, Israel. 

There are multiple times in Romans where Paul presents the misrepresentations of his teaching in the form of a question, then responds with May it never be! (Romans 3:4, 6, 31, Romans 6:2, 15, Romans 7:7, 13, Romans 9:14). Each of these questions is essentially in the same format, so it is likely that Paul is still answering the objectors. He asks, I say then, God has not rejected His people, has He (v 1)? And just like the other objections, Paul answers it immediately with: May it never be! No, God has not rejected His people.

Has He cast them away? No. That would mean He cast away Paul, who says I too am an Israelite, a descendant of Abraham, of the tribe of Benjamin (v 1). God foreknew His people, and He isn't finished with them (Romans11:2). Paul will argue in this chapter that Israel are still God's people. God still loves them. God will keep His promises to them, because His promises are irrevocable (Romans 11:29). 

The tribe of Benjamin was the historical tribe of Israel's first king, Saul. Paul's Jewish name was also Saul. There is a pattern in scripture of the second ascending over the first. Perhaps the Apostle Paul is the second Saul. He started off like the first Saul, persecuting God's church, and insisting on his own way. But then he learned humility, and became God's faithful servant. In this way the second Saul would become the faithful servant of the second David, Jesus Christ the Son of David (Matthew 1:1). Unlike the first Saul, who sought to kill David, in order to prevent him from ascending to the throne.