 Following the opinion of Duns Scotus (q. 36 of his Quaestiones in librum Praedicamentorum—Questions on the Book of the Categories), Burley maintains that the four ‘species’ of quality mentioned by Aristotle are not properly species but modes (modi) of quality. That is because unlike real species, they are not completely separate classifications, since many things belonging to the first species also belong to the second and/or the third (EP, ch. de qualitate, fol. 38vb).