The purpose of this study is: to identify the essence of Yezidism and its place in the system of representations of the peoples of Mesopotamia and Ancient Iran; analysis and systematization of available information about the Kurds - followers of Yezidism - and an attempt to resolve existing contradictions in questions about the essence of Yezidism and the ethnicity of its adherents; presentation of biographical information about Sheikh Adi ibn Musafir and characteristics of his activities, determination of the influence of his ideas on the reform of Yezidism