The Neoplatonist Plotinus (d. 270) raised a number of detailed difficulties with Aristotle’s account. The big problem, for him, was that if Aristotle’s scheme of categories is supposed to be a classification of all beings, it seems unable to accommodate those intelligible entities that are the primary beings from which all others emanate. Plotinus’ disciple Porphyry (d. 305) wrote two commentaries on the Categories, only one of which survives. He proposed an ingenious solution to Plotinus’ interpretive problem. The Categories should not be read as a pretended classification of all beings but as a classification of the species and genera of sensible beings. By this means, Aristotle’s book could be assimilated into Neoplatonic doctrine. Porphyry’s most famous work is the EisagOge - an introduction to the Categories - which contains the structure later known as Porphyry’s Tree, a detailed account of the way in which the category of substances branches out into its genera and species.
The Categories talks sometimes about ‘‘things that are said’’ (1a16) and sometimes about ‘‘things that are’’ (1a20). Thus, there arose the interpretive question of whether the work is about words or things. Porphyry proposed that the book is about words insofar as they are used to signify things. This compromise solution was to become influential in the Middle Ages.
The commentary on the Categories by Boethius (d. 524/525) takes over much of Porphyry’s thinking. For example, he says that the substances of which the Categories speaks are compounds of matter and form, and not such things as God or the soul.
In the eleventh century, some interpreters rejected Porphyry’s compromise concerning the subject matter of the Categories; they insisted either on reading the work as being about things [in re] or being about words [in voce].
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