 The Ikhwanian encyclopedia is typical of the changes in Greek science and philosophy during the tenth century as a result of the increasing Shî‘a influence. In the ninth century and at the beginnings of the tenth century, the prominent philosopher Abû Yûsuf Ya‘qûb b. Ishâq al-Kindî (d. ca. 870) had already developed single philosophical doctrines (e.g. in cosmology or psychology; an examination of the contents of Epistle 41 On definition and descriptions in the light of al-Kindî’s treatise with the same title is made by Poonawala in Baffioni, Poonawala 2017, 277 ff.). Though elaborating them in an original way, al-Kindî had not tried to combine such doctrines with the basics of Muslim faith. Theological considerations remain parallel with philosophical issues. The physician Muhammad ibn Zakariyyâ’ al-Râzî (d. ca. 925), mainly interested to natural philosophy, had even questioned the legitimacy of prophecy.