What is the theme in The Source; a Novel by James A. Michener?

The development of judaism. The Source is basically a journey through the history of the development of Judaism, from the days of paganism to the 1960s. It begins at Makor when Ur lives in a cave and is a pagan. After Ur, there are a variety of different pagan gods at the site, including Baal. When the god El-Shaddai appears, the emphasis begins to shift to monotheism and the beginnings of Judaism as he evolves into the god Yahweh.