I point out some unnoticed features of the interrelationships between episteme and doxa which help to explain some difficult texts and which I take to be archai for their definitive accounts. Much turns on how 'is' is to be understood, and whether or not it can be said to have different senses.
Turnbull, Robert G., "Episteme and Doxa: Some Reflections on Eleatic and Heraclitean Themes in Plato" (1978). The Society for Ancient Greek Philosophy Newsletter. 91.