Paul was the apostle to the Gentiles but he would still preach to those from Israel because he never knew who the remnant would be.

Romans 11:13-15 KJV

Paul tells the Gentiles not to feel superior to Israel because they know Jesus. But to be thankful to God for the opportunity. V.22 if we don't continue in our belief then we can also be cut off from God. Also if they believe they can come back to God.

Romans 11:16-24 KJV

Israel for the most part, is to be blind to God until all the Gentiles that are called by God respond to him. Then Israel as a whole will have their eyes opened to God and be drawn to him. Israel is still waiting for this future time of deliverance. God say's that it will happen. He say's that all Israel is to be saved. How is that possible if this present life is all there is, if this present life is mankind’s only chance to accept the salvation only Jesus can bring?

For salvation to come to people who are already dead. When the only way to be saved is to believe in the name of Jesus. Then those that are dead must have the chance to believe and be saved. As we have already read from previous scriptures the only mechanism that the bible teaches us so that they can come back to life to do that, is by the resurrection from the dead. Then they will have their opportunity for salvation. By the same resurrection of the dead all of mankind can have their chance to know God.

Romans 11:25-36 KJV