The Scripture Demonstrates That God Is Sovereign Over All Things And Has Mercy On Whom He Wills (9:14-18).
Paul recognises that what he has just demonstrated about God's elective mercy might raise the protest, ‘but surely that means that God is being unfair'. So he immediately deals with that charge on the basis of the Scriptures, demonstrating what God had proclaimed to Moses, and what was revealed in God's treatment of Pharaoh at the Exodus. The point behind these examples is that what he has already said about Israel is justified, and that God does what He wills because no man has any claim on Him on the basis of their goodness. He thus can have compassion on whom He chooses, and He can harden whom He chooses, because they have already all demonstrated their hardness of heart. By this he is bolstering his argument in the previous verses that God acts unilaterally on individuals and nations in order to further the fulfilling of His purposes.