In this controversial study, Aaron W. Hughes breaks with received opinion, which imagines two distinct religions, Judaism and Islam, interacting in the centuries immediately following the death of Muhammad in the early seventh century. Tradition describes these relations using tropes such as that of "symbiosis." Hughes instead argues that various porous groups-neither fully Muslim nor Jewish-exploited a shared terminology to make sense of their social worlds in response to the rapid process of Islamicization. What emerged as normative rabbinic Judaism on the one hand, and Sunni and Shi'a Islam on the other were ultimately responses to such marginal groups. The so-called "Golden Age" in places such as Muslim Spain and North Africa continued to see the articulation of this "Islamic" Judaism in the writings of luminaries such as Bahya ibn Paquda, Abraham ibn Ezra, Judah Halevi, and Moses Maimonides. Drawing on social theory, comparative religion, and primary texts, Hughes presents a compelling case for rewriting our understanding of Jews and Muslims in their earliest centuries of interaction. Not content to remain solely in the past, he examines the continued interaction of Muslims and Jews, now reimagined as Palestinians and Israelis, into the present.