Composed by Thomas of Marga, a bishop in northern Iraq (9th century), the Book of Superiors tells the story of Christianity in the Middle East between the 6th and 9th centuries. The Syriac text was edited and translated at the end of the 19th century, only to be largely neglected by scholars. The originality of Thomas' work can be seen in the depth of its historiographic reconstruction, coupled with a rigorous research method. The innovation of this proposal lies in a complete analysis of the contents of the Book, never attempted before, to bring light on the value and the wealth of information on events such as the Arab-Muslim Conquest and of the ways in which Christian religious groups adapted to the new circumstances. The ambition of the project is to locate the historical-religious perspective of The Book of Superiors in the context of the changing society of Late Antique Iraq. My research project will focus on some macro-themes that are developed by Thomas: the relationship with the Arab-Muslims, the "newcomers" in 7th century Mesopotamia; internal relations between the institutions of the Oriental Christianism; the relations and mobility between Thomas' world, the worlds of the Silk Road and the Mediterranean. These are the themes that allow us to reconstruct a unique view from the 9th century on issues that are still topical, in the Middle East and beyond, such as the encounter between religions, the mobility of people and ideas, and the representation of the past.