Genus and species are characteristics that determine every definition  . However, they are not   the only determining factors. These factors include the further moment of proprium and of differentia   specifica as such. These aspects, which guide concept-formation, are called predicables or κατηγορήματα. These κατηγορήματα were systematically treated for the first time by Porphyry in his introduction to Aristotle  ’s Κατηγορίαι. This Εισαγωγή was then translated into Latin by Boethius and became the basic text   on logical questions in the Middle Ages. The so-called controversy over universals of the Middle Ages developed in connection with this Εισαγωγή. (GA18  :15-16]