Book excerpt: The contributions to this volume enter into a dialogue about the routes, modes and institutions that transferred and transformed knowledge across the late antique Mediterranean and the Persian Gulf. Each contribution not only presents a different case study but also investigates a different type of question, ranging from how history-writing drew on cross-culturally constructed stories and shared sets of skills and values, to how an ancient warlord was transformed into the iconic hero of a newly created monotheistic religion. Between these two poles, the emergence of a new, knowledge-related, but market-based profession in Baghdad is discussed, alongside the long-distance transfer of texts, doctrines and values within a religious minority community from the shores of the Caspian Sea to the mountains of the southern Arabian Peninsula. The authors also investigate the outsourcing of military units and skills across religious and political boundaries, the construction of cross-cultural knowledge of the balance through networks of scholars, patrons, merchants and craftsmen, as well as differences in linguistic and pharmaceutical practices in mixed cultural environments for shared corpora of texts, drugs and plants.