Muhammad Abu 'l-Fadl Muhammad's (fl. ca. 800/1400) Persian Qamus al-bahrayn was written in 814/1411. About the author's life and times nothing is known other than that his nickname 'Hamid Mufti' points at a certain level of expertise in the legal profession. Being a theological summa, the Qamus al-bahrayn stands in a long tradition. The author used numerous theological and philosophical sources, referring explicitly to such authorities as Avicenna (d. 428/1037), Suhrawardi (d. 587/1191), Fakhr al-Din Razi (d. 606/1210), and Nasir al-Din Tusi (d. 672/1274). The work contains so many obvious borrowings from Razi that the Qamus al-bahrayn is factually an exposition of his thought. In the edition, a special effort was made to point this out in each case where a concrete reference could be given. There are few theological summae in Persian; readers of Persian will therefore be delighted to discover this comprehensive work and its mellifluous style of composition.