Epistemology:

1) "Zeno, the founder of the Stoic school, illustrated sensation by the outstretched hand, assent by the curled fingers, apprehension by the closed fist and knowledge by the grasping of one hand by the other (Cicero, Academica Priora 2.145 = LS 41 A); for knowledge for the Stoics is part of a whole system, and while individual statements can be true (or false), truth, as opposed to just 'what is true', is a property of the system as a whole."

2) "The problem is, of course, that while we receive many impressions of which we can be reasonably sure that they represent their sourecs accurately, it is less easy to find examples of individual impressions which simply could not be in any way distorted or misleading...A man can normally recognise hsi own wife without ther ebeing any doubt about the matter; but this was not so for Admetus in Euripides' play when his wife Alcestis had returned from the dead."

3) "The second important Stoic contribution to 'logic', in their own broad sense of the term, was their theory of the lekton or 'that which is said'. Consider Cato walking, and some who says out loud in Latin, with Cato in view but without pointing to him, 'Cato ambulat'. A person who does not know Latin will see the walking Cato - who is a physical object - and will hear the sounds the speaker utters, which are also physical objects (modifications of the air). But he or she will not connect the sounds with the physical object Cato behaving in a certain way, and has thus failed to apprehend a third, incorporeal thing, the lekton or what the words are actually saying." (this anticipates the modern distinction between sense and reference)

Sharples, R.W. Stoics, Epicureans, and Sceptics. Routledge: London, 1996.