  All theorizing about relations in the Middle Ages begins with Aristotle’s short treatise, the Categories. Due to historical circumstances, this Aristotelian text was one of the very few pieces of ancient Greek philosophy available in the Latin west between the seventh and twelfth centuries, and the only one to contain a systematic philosophical treatment of relations. In the Categories, Aristotle identifies relations as one of the ten highest kinds or categories (one of the so-called summa genera), and he devotes an entire chapter—the seventh chapter of the treatise—to distinguishing its members from those of the other categories (most notably, substance, quantity, and  quality).[1]  On the standard medieval interpretation of this chapter, Aristotle is attempting to characterize relations at least partly on the basis of semantic or logical considerations—that is, on the basis of the differences between statements containing relational (or ‘relative’) terms and those containing only non-relational (or ‘absolute’) terms. As we shall see, this approach to characterizing relations helps to shape the way medieval philosophers understand them, and gives rise to the common medieval distinction between relations merely according to speech (relationes secundum dici) and relations according to nature or being (relationes secundum esse).