Paul is obviously working out some of his own struggle with the Jews not automatically being part of the Kingdom inaugurated by Christ. No wonder. The Pharisee life had defined who he was, and meeting Christ left him in a real identity crisis. He’s working that out here, really trying to keep the good news out front: no, you’re not automatically in because you’re Abraham’s child. But you can still be in the Kingdom through Christ, he’s calling all his people out. There’s also a tinge of mourning in this letter, too, because certainly he had friends whom he knows will never follow the way of Christ.