Had it been identical with quiddity...

Had it been identical with quiddity, or a part of it, such a negation would have been invalid, for it is impossible to negate something in regard to a thing which is identical with it or a part of it. Also, a proof is required if existence is to be predicated of a quiddity; therefore, it is neither identical with quiddity nor a part of it, because a thing’s essence ( dhat ) and its essential characteristics [i.e. genus and differentia] are self-evident and do not stand in need of a proof.

Moreover, quiddity is in itself indifferent ( mutasawiyat al-nisbah , lit. ‘equally related’) to existence and non-existence. Were existence identical with quiddity or a part of it, it would be impossible to attribute to it non-existence, which is its contradictory. الفصل الرابع في أ