Originally published in 1963, "Demonstration of the Truth" (Borhan ol-Haqq) presents for the first time a comprehensive and authoritative historical account of the mystical order of the Ahl-e Haqq, including its development, fundamental principles, and sacred rites, which until then had been kept secret. Written in a precise style resembling a legal text or catechism, "Demonstration of the Truth" codifies and harmonizes the practices and doctrines of the Ahl-e Haqq without any ambiguity. Indeed, Ostad's rigorous approach of cross-checking and critically examining all available sources, as well as inventorying and clarifying the various rites and practices of the Ahl-e Haqq (not to mention definitively establishing the calendar of saints) makes "Demonstration of the Truth" an important landmark in the history of the Ahl-e Haqq, whose doctrines and principles had never been the subject of such a systematic study.