This project aims at analyzing for the first time (im)purity language and discourses in Syriac sources written in the 4th-9th c., to highlight the specificities of Syriac Christianity vis-à-vis other ancient strands. In particular, it will verify the existence of a Syriac specialized purity lexicon and chart the overlaps of the concepts of impurity and sin. Accordingly, it will produce the first database of Syriac purity lexicon of the 4th-9th c. Furthermore, it will focus on the ‘demarcational’ function of purity to analyze how discourses on transmission of impurity were used to create artificial borders. In the past decade, anthropologists have argued that purity norms are stricter in societies without strong boundaries. The Syriac world is an ideal field to further test this approach: lacking political and confessional unity, Syriac communities had to continually negotiate their internal and external boundaries. This project will investigate how purity discourses were used in anti-heretical and polemical works (against Jews, Muslims, and Zoroastrians, among whom Syriac people lived), and whether Zoroastrianism and Islam influenced Syro-Christian purity ideas. It will produce the first monograph analyzing Syriac purity ideas diachronically, and across literary genres and geo-ecclesiastical borders. Hence, it will contribute not only to the understanding of Syriac Christianity, but also to the study of Syriac contacts with Muslims, Jews, and Zoroastrians.