  One more point needs to be made clear. Aristotle never clearly and consistently ties the categories to sentential or propositional structure. In Categories he appears to consider them in isolation from their syntactical context, but in Topics (103b20–27) and Metaphysics (1017a23–25) he seems to tie them to predication and, thus, to consider them in relation to a syntactical context. This ambiguity gives rise to different interpretations, such as that of Frede, who considers them to be kinds of predications (1987), and that of Ryle, who views them as independent from syntactical context (1971). In short, the picture is far from clear, and this serves to separate Aristotle from authors who explicitly and exclusively view categories as reflecting syntactical contexts.