Stoicism

6. The ‘categories’

Aristotle developed a complex ontological scheme, his ten ‘categories’ (see Aristotle §7; Categories). The Stoics, following not Aristotle but the early Academy, recognized just two categories: that is, they divided all existing things into absolute or per se items, and relative items. For example, a house or dog is something absolute, whereas to be a slave, or sweet, is relative: being a dog does not, as such, involve standing in any relation, but to be a slave is to be somebody’s slave, and to be sweet is to taste sweet to one or more percipients.

However, the Stoics also developed a more original, fourfold ontological classification, commonly known to modern interpreters as the Stoic ‘categories’, although it is unlikely that they used this term for it, and it is safer to call them ‘genera’. It is disputed what the origins and purpose of this scheme were, but its most interesting recorded uses are to account for individual identity over time, and to amplify the thesis described in §3 that ‘being’ belongs only to bodies.

According to this classification, any given item may be seen as: (1) a mere ‘substrate’ (hypokeimenon); (2) something ‘qualified’ (poion); (3) something ‘disposed in a certain way’ (pōs echon); and (4) something ‘disposed in a certain relation’ (pros ti pōs echon).

To start with the first pair. To pick out a thing as (1), a ‘substrate’, is merely to individuate it as a (temporary) lump of matter, for example, by pointing at it. To mark it as (2), something ‘qualified’, is to distinguish it by one or more qualities which it possesses. Here the Stoics have a precise physical analysis of what a quality is: a portion of pneuma imbuing the thing, whether as its soul or as some other inherent property, for example, its colour or its weight. There is a further subdivision of the ‘qualified’ into (a), what is ‘commonly qualified’, for example, dog, human, wise, green, and (b), what is ‘peculiarly qualified’, for example, Fido, Socrates. These correspond, roughly, to what is signified by (a) common nouns and adjectives, and (b) proper names.

It is the first pair that is invoked to explain diachronic identity. Such identity had been challenged by the growing argument (auxanomenos logos), a puzzle much favoured by the Stoics’ sceptical opponents in the New Academy. This argument objected that any ‘growth’, however slight, must generate a new individual, since a body with even one new particle added is not the same body as before; therefore there can be no enduring subject of growth; and hence no growth. The Stoic answer is that what endures as the subject of growth is not the material substrate (or ‘substance’, ousia), but the ‘peculiarly qualified individual’. Qua ‘substrate’ Dion (to use the Stoics’ favourite stock name) has little if any endurance, but qua ‘peculiarly qualified individual’ (idiōs poios), that is, qua Dion, he endures throughout his life. Although Dion’s matter constantly changes, the individuating quality that makes him Dion is with him, unchanged, from birth to death. That there is such a lifelong peculiar quality is a thesis of Stoic physics (there is no evidence what they thought it consisted in; the uniqueness of fingerprints is a modern discovery), but the need to solve the growing argument elevates it to the status of a metaphysical necessity. It also plays a part in Stoic epistemology (see §12).

As well as being (1) a lump of matter, and (2) both (a) human, wise and so on and (b) Dion, he is also at all times (3) in some disposition or other, for example, sitting, and (4) in some relation, for example, the person on my right. Here (3) and (4) represent the final two genera. The third genus, ‘disposed in a certain way’, is widely used to analyse as corporeal items commonly believed to be incorporeal (see §3). For example, knowledge is analysed as ‘the commanding-faculty of the soul disposed in a certain way’ – where the soul itself is corporeal, being pneuma. The fourth genus has similar analytic uses. What is special about it as a mode of being is that it picks out, not all relative items, but those whose being what they are is wholly parasitic on that relation, so that they could cease to exist merely because their external correlate changes or perishes. Suppose Dion is Theon’s accomplice. Qua Dion he may continue to exist despite Theon’s desertion or death; but qua accomplice he cannot. Hence ‘accomplice’ is a fourth genus item, while ‘Dion’ is not. For an important debate about the status of virtue, using this fourth genus, see §16.