The Concept of ‘Differentia’ in Avicenna’s Philosophy and that of Sohrawardi And its Evolution in Mulla Sadra’s Philosophy

Differentia’ is the only concept among the ‘Five Universals’ that is not essentially quidditative. It is neither ‘essence’ nor ‘accident’. Rather, it is, as Avicenna puts it, the most general concept. Generality of the concept ‘differentia’ and its being out of the circle of categories can show its being existential, which Avicenna does not assert anyway. For Sohrawardi, the concept ‘differentia’ has basically no place in his philosophy due to its simple light quiddity. And in logic, he rejects the limit elements, i.e. genus and differentia, by criticizing Peripatetic definition. Considering Sohrawardi’s critics of elements of quiddity and inspired by Avicenna, Mulla Sadra asserts, based on principality of existence, that the concept of ‘differentia’ is existential. For Mulla Sadra, the form of mode of existence of a thing is in outside, whose negatively conditioned consideration, i.e. the very ‘differentia’, is a philosophical concept, not a quidditative one. In this article, we show how the ‘differentia’ returns from its logical position to its originally philosophical position, and turns into one of the essential accidents of existence as it is.