The present article aims to show that the treatise On the Harmonization of the Opinions of the Two Sages the Divine Plato and Aristotle cannot have been written by al-Fārābī. It considers to this end four crucial issues treated in this work, concerning (1) divine Providence and the particulars, (2) Platonic Ideas and the divine Intellect, (3) creation ex nihilo and (4) the divine attribute of ‘will’. It establishes in each case that the thesis defended by the author is contrary to al-Fārābī’s doctrine and akin to that of Yaḥyā ibn ‘Adī. This twofold result prompts us to suggest that the author should be associated with Ibn ‘Adī and his milieu; it also suggests a new periodization of 10th century Arabic philosophy. Rather than imagining a Kindian phase followed by a ‘‘school of Baghdad’’ extending from al-Fārābī’s masters to the age of Avicenna, we should postulate that some of al-Fārābī’s followers returned to al-Kindī in the field of cosmology, for theological reasons.