Philosophical Fragments  

"As long as I keep my hold on the proof, i.e., continue to demonstrate, the existence does not come out, if for no other reason than that I am engaged in proving it; but when I let the proof go, the existence is there." (...) "unless we hold fast to the Socratic doctrine of Recollection, and to his principle that every individual man is Man, Sextus Empiricus stands ready to make the transition involved in "teaching" not only difficult but impossible; and Protagoras will begin where Sextus Empiricus leaves off, maintaining that man is the measure of all things, in the sense that the individual man is the measure for others, but by no means in the Socratic sense that each man is his own measure, neither more nor less. Philosophical Fragments