Aziz Mahmud Hüdayi was one of the most important spiritual, political and intellectual figures of the Iate sixteenth and early seventeenth century of the Ottoman Empire and his memory is stili alive in the present-day Turkish society. His life-span corresponds to the crucial period of the Ottoman history which is marked by a series of significant developments both within and outside the Empire. The first part of this study is devoted to the turning points in Aziz Mahmud Hüdayi' s life in the light of the primary (Ecvibe-i Mutasavvifane, Letters to Halil Paşa, Tezakir) and the secondary sources on the concepts that form the basis of dervish life; on Ottoman ilmiyye organisation; on the origins, history and ·basic principles of the Celvetiyye order; on the development of opposition movements to the growing centralisation and consolidation of the principles of siinnf Islam within the Ottoman Empire; and on some significant political figures of the age who w ere influential in Aziz Mahmud Hüdayi' s establishing himself as the şeyh of the sultans. The second chapter is an evaluation of his correspondance with two of his followers, Ecvibe-i Mutasavvifane and Letters to Halil Paşa, and of the letters he wrote to the sultans, Tezakir. The third part of this study is about Aziz Mahmud Hüdayi' s comments, as fo und in Tezakir, on politics, which is treated within the context of the nasihatname genre, and on piety, which is treated within the context ofthe Kadızadeli movement. Appendix I is an overview of the literary outputs of Aziz Mahmud Hüdayi and their present state of publication. Excerpts from Tezfikir that have been referred to in the text are given in their original form in Appendix II.