  Although commentaries on Aristotle's Categories written before 1200 tend to be expository, still they raise important philosophical questions, such as whether the categories time and place are synonymous with when and where, or whether action and passion are reducible to motion. Even more important is the lively debate between realists and nominalists concerning whether categories are words, concepts, or things (for Abelard's influence, see Marenbon 1997, 108). The position they take on it determines the discipline in which they think the categories are studied and affect the degree of isomorphism they believe holds between language (words), thought (concepts), and reality (things). If Aristotle's Categories is a book about words, then categories are studied in grammar; if it is about concepts, they are studied in logic; and if it is about extra-mental things, they are studied in metaphysics.