Islam emerged amid flourishing Christian and Jewish cultures, yet students of Antiquity and the Middle Ages mostly ignore it. Despite intensive study of late Antiquity over the last fifty years, even generous definitions of this period reach only the eighth century, whereas Islam did not mature sufficiently to compare with Christianity or rabbinic Judaism until the tenth century. Before and After Muhammad suggests a new way of thinking about the historical relationship between the Abrahamic religions, integrating Islam into European and West Asian history.

Garth Fowden identifies the whole of the First Millennium--from Augustus and Christ to the formation of a recognizably Islamic worldview by the time of the philosopher Avicenna--as the proper chronological unit of analysis for understanding the emergence and maturation of the three monotheistic faiths across Eurasia. Fowden proposes not just a chronological expansion of late Antiquity but also an eastward shift in the geographical frame to embrace Iran.

In Before and After Muhammad, Fowden looks at the Abrahamic monotheisms alongside other important developments in Greek philosophy and Roman law, to reveal how the First Millennium was bound together by diverse exegetical traditions that nurtured and fed off each other.