Recent theorizing has emphasized the concept of “difference” and how its normative deployment orders our knowledge of the world. This ethical determination of how we know, however, is only half of a loop as difference has epistemological roots. It is precisely the concept’s inherent connection to the epistemological demand that we must be certain of what we know that underprops it as a contemporary problematic. This demand is basic to philosophy since ancient times. We find it, for example, in the late Platonic dialogues Theaetetus and Sophist as Plato endeavors to define and account for knowledge and true belief. We also find this in Aristotle’s Categories, which not only underpins his other philosophical works, but also founds the categorialism still current in philosophical thinking. We can think of categorial thinking as defining and structuring what we can know. And insofar as our knowledge guides our practice, categorial thinking also defines and structures our reality. In this essay, I perform a simple content analysis of the Categories. The aim is to look for difference and its variants, to count how many times they appear, to identify the general and specific contexts of their appearance, to find related terms and concepts in the specific context of the sentences that they appear in. The essay’s analyses try to find explanations as to what Aristotle’s concept of difference is, as to what Aristotle think of it as it appears in various contexts in the Categories, as to how it reflects the structure of our knowledge of the world, and as to how it likewise reflects the manner by which we attempt to structure or order our world.