Stoicism

10. Dialectic

Dialectic is the main branch of what the Stoics called ‘logic’, and amounts, roughly, to the science of argument. Although dialectic was both theorized and applied in innumerable treatises, the Stoics never lost sight of the Platonic conception of it as a fundamentally two-person activity, involving the interrogation of an interlocutor. ‘Dialectic’ actually means ‘the science of dialogue’. The science of rhetoric differed from dialectic precisely in being the science of producing a good monologue, and was treated as a separate branch of logic. There was no uniform Stoic view as to whether theory of knowledge (see §§12–13) counted as part of dialectic, or as a third branch of logic.

In so far as it is concerned with argument, dialectic has distinct parts dealing with (1) signifiers and (2) significates. The former are words (and hence bodies; see §8), and Stoic dialectic’s concern with language as such led it, among other things, to develop the first real grammatical theory in Western thought. It became the basis of all subsequent work on grammar in antiquity and far beyond.

The latter term, ‘significates’, designates lekta (see §8), the incorporeal meanings which in their complete form are expressed only by whole sentences. Stoic logic (to use the word now in its modern sense) concentrates on one species of lekta, the declarative ones, called axiōmata. This term, literally ‘judgments’, is more familiarly translated as ‘propositions’. Stoic logic is indeed the first fully developed propositional or sentential logic. In this it differs radically from Aristotelian logic, which is a logic of terms (see Logic, ancient). The origins of Stoic logic probably lie less in Aristotle than in the work of the Dialectical school (see Dialectical school; Diodorus Cronus; Philo the Dialectician).