The Ikhwan al-Safa' (Brethren of Purity), the anonymous adepts of a tenth-century esoteric fraternity based in Basra and Baghdad, hold an eminent position in the history of science and philosophy amongst Muslims due to the wide reception and assimilation of their monumental encyclopaedia, the Rasa'il Ikhwan al-Safa' (Epistles of the Brethren of Purity). The present volume is the fourth of this definitive series consisting of the very first critical edition of the Rasa'il in Arabic, complete with the first fully annotated English translation. Prepared by James Montgomery and Ignacio Sanchez,...