Theory and History of Ontology by Raul Corazzon | e-mail: rc
"In addition to developing the hypothetical syllogism, Stoic logic also elaborated categories, which likewise stand in contrast to Aristotelian thought. The Stoics teach that there are four categories: substance, quality, disposition, and relative disposition.(140) Rather than being horizontal, signifying aspects of an enduring substance which are accidental and which can be shorn from it without destroying its essence, the Stoic categories are vertical. They move from lesser to greater levels of concreteness. None is accidental; all must be present in a given reality if that reality is to be grasped in all its individuality. Substance denotes the materiality of a thing and is possessed by everything except the incorporeals. Quality denotes the way in which matter is organized to form an individual being. Disposition includes times, places, actions, size, and color. It describes the particular situation and attributes of the individual. All the features covered by the category of disposition, including color,(141) are regarded by the Stoics as inherent in the individual. This view harmonizes with the doctrine in Stoic physics that bodies create their own extension and their own time and space, so to speak, through their tonos and activity. Relative disposition denotes the way that an individual thing is related to other phenomena. None of the four Stoic categories can be removed from an individual being without that being ceasing to be itself. At each level of specificity the categories refer to something integral to the individual being's reality. The categories mirror the physics of concrete individual events taught by the Stoa. Although officially classified under logic, the Stoic categories are really pertinent to physics since they are modes of expressing reality.(142)"
(142) Bochenski, Ancient Formal Logic, p. 87; Bréhier, Chrysippe, pp. 132-33; Phillip De-Lacy, "The Stoic Categories as Methodological Principles,"Transactions and Proceedings of the American Philological Association, 76 (1945), 246-63; Goldschmidt, Le système stoïcien, p. 23; Sambursky, Physics of the Stoics, p. 18; Sandbach, The Stoics, pp. 93-94. On the other hand, A. C. Lloyd, "Grammar and Metaphysics in the Stoa," in Problems in Stoicism, ed. Long, p. 65 and Rist, Stoic Philosophy, pp. 15260 argue that the categories should be regarded entirely as lekta. (pp. 55-56)
From: Marcia L. Colish, The Stoic Tradition from Antiquity to the Early Middle Ages. I. Stoicism in Classical Latin Literature, Leiden: Brill 1985.