  160b–d summarises the whole of 151–160. Socrates shows how the exploration of Theaetetus’ identification of knowledge with perception has led us to develop a whole battery of views: in particular, a Protagorean doctrine of the incorrigibility of perception, and a Heracleitean account of what perception is. Thus “perception has one of the two marks of knowledge, infallibility” (Cornford 1935, 58); “and, if we can accept Protagoras’ identification of what appears to me with what is, ignoring the addition ‘for me’ and the distinction between being and becoming, the case will be complete.”