Stoic logic is in its core a propositional logic. Stoic inference concerns the relations between items that have the structure of propositions. These items are the assertibles (axiômata). They are the primary bearers of truth-values. Accordingly, Stoic logic falls into two main parts: the theory of arguments and the theory of assertibles, which are the components from which the arguments are built.

SAYABLES AND ASSERTIBLES

What is an assertible? According to the Stoic standard definition, it is

This definition places the assertible in the genus of self-complete sayables, and so everything that holds in general for sayables and for self-complete sayables holds equally for assertibles. Sayables (lekta) are items placed between mere vocal sounds on the one hand and the world on the other. They are, very roughly, meanings: ‘what we say are things, which in fact are sayables’ (DL VII 57). Sayables are the underlying meanings in everything we say or think; they underlie any rational presentation we have (S. E. MVIII 70). But they generally also subsist when no one actually says or thinks them.