 This cosmological account, however, calls for explaining how separate intellects are differentiated. After all, separate intellects share the feature of immateriality, hence they cannot be numbered. Furthermore, considering the fact that separate intellects share the same epistemological content (i.e., the forms of all existents derived from the First Intellect) and that the knower is identical with the object known, according to the Aristotelian dictum of “cognitive identity”, separate intellects should all be identical. In the Avicennian-emanative scheme, intellects are numbered on account of the causal relation between them, each intellect being the cause of an intellect emanating from it and “only God, who is at the top of the series is an uncaused caused” (Wolfson 1958 : 244). By rejecting the conception of an emanative causal relationship between intellects, Albalag, however, could not speak of a distinction in terms of causal relation. Alternatively, he follows Averroes in positing ontological hierarchy as the differentiating factor between intellects (Tahāfut al-Tahāfut: fifth discussion: 173). While each separate intellect derives its knowledge directly from the First Intellect, each stands in a specific hierarchical relation to the First Intellect, the ranking of each intellect being in accordance with the extent of purity of its mode of apprehension; the purer and simpler the mode of apprehension the closer the intellect in rank to the First Intellect. Overlap between these modes is not possible, which ensures that separate intellects remain differentiated.