 As should be clear from this brief discussion, providing a complete derivation of Aristotle’s categorical scheme would be a difficult, indeed perhaps impossible, task. After all, someone might conclude that Aristotle’s categorial scheme was either in part or in whole mistaken. Minimally, the task is a daunting one. But of course, the difficulty in establishing its ultimate correctness is not peculiar to Aristotle’s categorial scheme. Indeed, it should not be at all surprising that the difficulties that have beset metaphysical speculation in the Western tradition can be seen in such a stark and provocative fashion in one of the great founding works of that very tradition. In fact, it is in part due to such difficulties that external questions about categorial and other metaphysical structures arise. Such difficulties understandably lead to questions about the legitimacy of category theory and metaphysical speculation in general. Unfortunately, the history of metaphysical speculation has shown that it is no less difficult to establish answers to external than to internal questions about category theory. That acknowledged it is noteworthy that questions of both sorts owe their first formulations, ultimately, to the categorialism of Aristotle’s seminal work, the Categories.