[T]here can be a causal science of categories, inasmuch as there can be a causal science of things belonging to the categories. Kilwardby remarks, however, that the real philosopher, and not the logician, studies categories as composed of matter and form, for it is the real philosopher who deals with the principles of material things. Studying the principles of sensible substances, the real philosopher can first ascend from material to immaterial substances, then he can further ascend from the multiplicity of immaterial substances to the highest immaterial substance, i.e. God.
--Geogio Pini, Categories and Logic in Duns Scotus, Chapter One.
Pini's excellent book nevertheless contains a mistake here. The Kilwardby passage from which the above remarks are taken is as follows:
Et hec cognicio est propria primo philosopho; considerat enim in principiis substancie sensibilis, et consequenter in principiis substancie insensibilis, reducens omnes substancias sensibiles ad insensibiles, et insensibiles omnes ad unam . . ."
Note that Pini begins talking about sensible substances and then speaks of ascending to immaterial substances, up to the highest immaterial substance. Kilwardby, in contrast, speaks of sensible and insensible substances throughout. Pini shares here the extremely common prejudice that insensible substances are obviously also immaterial, and thinks nothing of conflating the two terms. This is dangerous, however, when Kilwardby is speaking of matter and form as the foundation for understanding things belonging to categories, for if insensible substances are themselves composed of matter and form, they can be included under (at least some of) the same categories as sensible substances. Now Kilwardby, although a Dominican, does in fact accept spiritual matter, as Pini might have learned from Kleineidam. The point doesn't seem to have occurred to him, though.
This is not a jab at Pini. I'm 1/3 through the book and it is otherwise very good.