This chapter examines the medieval Greek and Arabic sources for the movement of medical substances between the Byzantine and Islamic worlds in the period from the ninth to the twelfth centuries. Although commerce was the most common means employed in the movement of materia medica, and the part played by tribute taking and looting was not negligible, the role of diplomatic gift exchange cannot be ignored. A relatively wide range of drugs were exchanged, ranging from theriac and a stone against dropsy to spices and perfumes. Moreover, this chapter examines the peculiar role of drugs as gifts in diplomatic communication compared to more typical diplomatic gifts such as expensive textiles and luxurious objects. Not suited to acting as objects of display, materia medica seemed to convey a personal message of care, creating mutual ties between the sender and the recipient.

Between the eleventh and twelfth centuries a new class of authors specifically interested in classical philosophical texts appeared in Byzantium. After a long hiatus, these authors embarked upon a new adventure by producing commentaries on ancient philosophical texts. Their works are highly sophisticated and came to shape the Byzantine cultural landscape in this period and beyond. This chapter presents a survey of the middle Byzantine commentaries on philosophical works. For the first time, issues such as the conception of authoriality displayed in these commentaries, the different textual approaches, the transmission of these texts and the peculiar way of life of the Byzantine commentators are discussed and investigated from the point of view of the material and social conditions that favoured the production of these new texts.