Sextus Empiricus Pyrrhoniae Hypotyposes 2.11.107

[107] Such is the Stoic doctrine. But we assert, firstly, that it is non-evident whether any ‟expression” exists. For since some of the Dogmatists, the Epicureans, declare that expression does not exist, others, the Stoics, that it does exist, when the Stoics assert its existence they are employing either mere assertion or demonstration as well. If assertion, then the Epicureans will confute them with the assertion which states that no expression exists. But if they shall adduce demonstration, then since demonstration is composed of expressed judgements, and because it is composed of expressions will be unable to be adduced to confirm the existence of expression (for how will he who refuses to allow the existence of expression grant the reality of a system compounded of expressions?),