Epicureanism

5. Qualities

Atoms themselves have only the primary or ineliminable features of body: size, shape and weight. They lack the secondary properties of colour, flavour and so on. The ground for this parsimony is (Letter to Herodotus 54–5) that secondary properties are in their nature changeable, whereas atoms have been posited as the enduring entities which underlie change. Atomism instead treats colour and the like as purely macroscopic properties, caused by the individual shapes and overall arrangement of the constituent atoms in a compound body, and changed if that arrangement changes.Lucretius frequently compares the explanatory economy of this system to that of the alphabet, capable of generating endless different words simply by rearranging a modest stock of letters. In practice the crudely sketched atomistic explanations of macroscopic properties owe more to the shapes than to the arrangement of a thing’s constituent atoms (fluids consist of smaller and rounder atoms, sweet things of smoother ones…), although the degree of separation between atoms plays some part.

There are two kinds of properties (symbebēkota). ‘Permanent accompaniments’ (Greek ta aidion parakolouthounta, Latin coniuncta) are essential to a thing’s very existence, for example, tangibility for body and heat for fire, while accidents (symptōmata) are non-essential, for example, slavery or poverty for a human being. It is crucial to note that no ontological priority is implied for the properties of atoms over those of phenomenal bodies. The earlier atomist tradition had tended to treat atoms and void alone as real, with phenomenal properties mere arbitrary constructions placed upon them by the human mind and sense organs. This had led atomism in the direction of epistemological scepticism, a tendency which Epicurus himself strenuously resists. In discussing the status of properties (Letter to Herodotus 68–71), he emphasizes that although undoubtedly different from the per se existents, body and void, they are no less real for that. (The second-generation Epicurean Polystratus adds that even relative properties such as ‘beneficial’ and ‘harmful’, often decried as unreal by sceptics, have clear causal effects.) Accidents, in fact, have no existence at the microscopic level (Letter to Herodotus 70), and yet are real. This is a clear indication that Epicurus is consciously opposed to the atomist reductionism of his predecessors: colours and other accidents are real, yet irreducibly different from atomic structures. Although atomic structures are causally prior to the phenomena which they generate, they are in no way ontologically privileged over them.