The divine promises to Abraham have long been recognized as a key to the book of Genesis as a whole. But their variety, often noted, also raises literary and theological problems. Why do they differ each time, and how they related to each other and to the story of Abraham? Williamson focuses on the promises is Genesis 15 and 17, and concludes that they are concerned with two distinct but related issues. Genesis 15 guarantees God's promise to make Abraham into a great nation, while Genesis 17 focuses chiefly on God's promise to mediate blessing (through Abraham) to the nations. The two chapters are connected, however, by the theme of an individual, royal descendant who will come from the nation (Israel) and mediate blessing to all the nations of the earth.
