M. F. Burnyeat, Idealism and Greek Philosophy: What Descartes Saw and Berkeley Missed, in G. Vesey (ed.), Idealism Past and Present, Cambridge UP 1982, 19-50

These: Erst Descartes habe den Idealismus als Standpunkt möglich gemacht, daher kann sich Berkely nicht auf griechische Quellen (etwa Theait. 160A) berufen.

Greek philosophy does not know the problem of proving in a general way the existence of an external world. That problem is a modern invention. (...) The characteristic worry, from Parmenides onwards, is not how the mind can be in touch with anything at all, but how it can fail to be (p. 33).

Burnyeat belegt dies auch an Parm. 132BC:

Thought is relative, essentially of something else, and therefore it is incapable of furnishing the ultimate explanation of anything (p. 35).

Antiker Skeptizismus:

... the sceptic has no prior commitment to the thesis that perception or appearance is knowledge (p. 36).
First, and this is something Sextus is entirely explicit about, the sceptics doubting and suspending judgement extend only to statements which make claims about how things are in themselves (p. 37).
'True' in these discussions always means 'true of a real objective world', and that is how 'true' has been used since Protagoras and before. (...) Never, for example, does he [Sextus] claim that the sceptic can be certain of 'appearing'-statements or that he knows his own experinences (p. 38f.).

So far as I can discover, the first philosopher who picks out as something we know what are unambiguously subjective states, is Augustine (Contra Academicos III,26) (p. 40).

So it is not surprising, if Descartes thinks that he has found examples of knowledge and truth which lie beyond the reach of the traditional sceptical arguments, that these examples should turn out to be truths which an ancient sceptic would hardly have recognized as truths at all (p. 48).

Das Urteil schränkt Newman ein:

it is not so obvious that the more radical 'Cartesian' doubt was a later invention (p. 513, fn. 42).