According to Steiner, the original Mu‘tazilite heresy arose in the bosom of Islam, independently of any foreign influence, but, however that may be, its later development was largely affected by Greek philosophy. We need not attempt to follow the recondite speculations of Abú Hudhayl al-‘Alláf († about 840 A.D.) of his contemporaries, al-Naẓẓám, Bishr b. al-Mu‘tamir, and others, and of the philosophical schools of Baṣra and Baghdád in which the movement died away. Vainly they sought to replace the Muḥammadan idea of God as will by the Aristotelian conception of God as law. Their efforts to purge the Koran of anthropomorphism made no impression on the faithful, who ardently hoped to see God in Paradise face to face. What they actually achieved was little enough. Their weapons of logic and dialectic were turned against them with triumphant success, and scholastic theology was founded on the ruins of Rationalism. Indirectly, however, the Mu‘tazilite principles leavened Muḥammadan thought to a considerable extent and cleared the way for other liberal movements, like the Fraternity of the _Ikhwánu ’l-Ṣafá_, which endeavoured to harmonise authority with reason, and to construct a universal system of religious philosophy. [Sidenote: The Ikhwánu ’l-Ṣafá.] These 'Brethren of Purity,'[692] as they called themselves, compiled a great encyclopædic work in fifty tractates (_Rasá’il_). Of the authors, who flourished at Baṣra towards the end of the tenth century, five are known to us by name: viz., Abú Sulaymán Muḥammad b. Ma‘shar al-Bayusti or al-Muqaddasí (Maqdisí), Abu ’l-Ḥasan ‘Alí b. Hárún al-Zanjání, Abú Aḥmad al-Mihrajání, al-‘Awfí, and Zayd b. Rifá‘a. "They formed a society for the pursuit of holiness, purity, and truth, and established amongst themselves a doctrine whereby they hoped to win the approval of God, maintaining that the Religious Law was defiled by ignorance and adulterated by errors, and that there was no means of cleansing and purifying it except philosophy, which united the wisdom of faith and the profit of research. They held that a perfect result would be reached if Greek philosophy were combined with Arabian religion. Accordingly they composed fifty tracts on every branch of philosophy, theoretical as well as practical, added a separate index, and entitled them the 'Tracts of the Brethren of Purity' (_Rasá’ilu Ikhwán al-Ṣafá_). The authors of this work concealed their names, but circulated it among the booksellers and gave it to the public. They filled their pages with devout phraseology, religious parables, metaphorical expressions, and figurative turns of style."[693] Nearly all the tracts have been translated into German by Dieterici, who has also drawn up an epitome of the whole encyclopædia in his _Philosophie der Araber im X Jahrhundert_. It would take us too long to describe the system of the _Ikhwán_, but the reader will find an excellent account of it in Stanley Lane-Poole's _Studies in a Mosque_, 2nd ed., p. 176 sqq.