 Here the Perfect City is relying on the conclusion of the Book of Letters that “circumscribed by its quiddity” is one of the meanings of “being” and the conclusion of the On the One that “circumscribed by its quiddity” is one of the meanings of “one”, and using these conclusions to interpret Aristotle’s claim in Metaphysics IV,2 that “being” and “one” are mutually entailing. Any being X has a “specific existence” which “circumscribes it”, i.e., distinguishes it from all other things, and it is one in the sense that it is uniquely specified by this existence. If X is a member of a species, then X’s “specific existence” might include the matter or the place or other accidental attributes which distinguish X from other members of the same species. But, Fârâbî is saying, if X is the First and therefore indivisible in its substance, it cannot have both a quiddity which it shares with other things and then a distinct “specific existence” which distinguishes it from those other things. So because it is one both as “unique” and as “indivisible”, its unity, that by which it is one, is completely identical with the quiddity by which it exists [is a being]. Here, as with the other attributes which he demonstrates of the First, Fârâbî is paralleling the Muʿtazilite pattern of asserting that, for any attribute F such that we can say that God is F, the F-ness through which God is F is identical with the divine essence. But Fârâbî claims to have based his account of the First and its attributes on demonstrations grounded in analyses of the meanings of being, unity, intelligence and the other fundamental philosophical concepts; whereas, Fârâbî would say, when the Muʿtazilites say that God is F through an F-ness which is identical with his essence, and therefore is F in a different way from creatures, this is bare assertion to save their theses that God is simple and that he is nonetheless F, and does not rest on an analysis of a special sense of F that applies to God and how it relates to more ordinary senses of F. In the cases of being and unity, the special metaphysics of the Perfect City and Political Regime is supposed to rest on the general metaphysics of the Book of Letters and On the One, and is supposed to vindicate Fârâbî’s claim that Aristotelian general metaphysics, when properly understood, will give the path to a scientific special metaphysics.