The Stoics defined dialectic as ‘the science of what is true, what is false and what is neither true nor false’. This means that dialectic is a science with a specific object, the lekta or sayables. There seem to be conflicting sources concerning their status. According to Sextus, lekta are meanings correlated to thought and language. An alternative theory attributed to Diogenes of Seleucia, introduces them as predicates. In addition, the theory of complete sentences presents them as items combined by the expressions of vocal sound that signify them. Finally, sayables seem first to appear in physics as the incorporeal effects of corporeal causes and do not belong to dialectical contexts alone. These different aspects of the sayables are shown to be different moments of one process, from what happens to a body to its expression understood through cognition and language communication. Thus the notion of a sayable shaped Stoic dialectic not only as a science of signifying sounds and sayables, but also as a technique of argumentation by question and answer that reflects the asymmetry of cause and effect in physics by the asymmetry of name and verb in logic.