During the last 15 years several important sources have been published allowing the appraisal of the role of ulema during the Iranian constitutional movement (1906–11) and thus opening new lines of research. The 2006–7 edition compiled by Muhsin Kadivar from several unknown documents written by Akhund Muhammad Kazim Khurasani (d. 1330/1911) make it possible to measure his importance and his impact on the evolution of the events as well as his ideological influence. The usuli rationalist jurist Akhund Khurasani was considered at the beginning of the constitutional movement as one of the principal mujtahid and marja’-i taqlid of the Shiite world, and was possibly the best-known. After introducing the life and work of Akhund Khurasani and the theoretical principles (nazari) that he uses to define the constitutional movement, the main topics that arise in the study of this literature are identified. Particular attention is paid to his position as a rallying point and legitimizing force, his enthusiasm for an ambitious progressive policy, his intricate relations with western powers and his links with the Qajar.