That he should be the heir of the world (to klhronomon auton einai kosmou). The articular infinitive (to einai) with the accusative of general reference in loose apposition with h epaggelia (the promise). But where is that promise? Not just Genesis 12:7 , but the whole chain of promises about his son, his descendants like the stars in heaven, the Messiah and the blessing to the world through him. In these verses ( Genesis 13-17 ) Paul employs (Sanday and Headlam) the keywords of his gospel (faith, promise, grace) and arrays them against the current Jewish theology (law, works, merit).