On Aristotle's "Categories 5-6"

"Chapters 5 and 6 of Aristotle's Categories describe his first two categories, Substance and Quantity. It is usually thought that Plotinus attacked Aristotle's Categories, but that Porphyry and Iamblichus restored it to the curriculum once and for all. However, Frans de Haas stresses that Porphyry drew much of his defense of Aristotle from Plotinus' critical discussion.".

"Simplicius' commentary is the most comprehensive account of the debate on the validity of Aristotle's Categories. Simplicius discusses where the differentia of a species (for instance, the rationality of humans) fits into the scheme of categories. Another is why Aristotle elevates the category of Quantity to second place, above the category of Quality. Further, de Haas shows how Simplicius arrives at multiple definitions of "universal" to solve some of the problems."--BOOK JACKET.