ABSTRACT
In the exposition of the theory of perception and the discussions associated with it Protagoras’ doctrine about truth has been grounded in the flux theory so far as its implications for Theaetetus’ views on knowledge are concerned. His theory that what seems to be the case https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315694740/4cca3edf-e515-4bd0-9c2c-7c7b69d7080f/content/pg59_1_B.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> to each person is the case for him has been taken (152c 1–3) to imply that what appears to each person in perception is true for him who perceives it, on the ground that in the case of perceptual properties seeming to be, e.g., red amounts to being perceived as red (152b 11). The flux theory was then brought in and developed as a means of defending his view in its application to perception and perceptual judgments. But of course Protagoras meant to be upholding a universal thesis about truth and wished to assert that whatever a person might make (sincerely) an assertion about he necessarily said something true about it–as true, that is, as anything anyone could ever assert. When, therefore, Socrates begins his criticism of the theories he has just managed to amalgamate in his account of perception, he undertakes to test and refute Protagoras’ thesis understood in its largest sense. The effect of refuting it as a general doctrine about truth, and not merely one concerning the truth of reports of perception, will be to take one prop out from under Theaetetus’ sense-perception theory of knowledge. For if Protagoras’ doctrine about truth is false, in general, then the question whether it is true within the limited field of perception will have to be examined on its own merits; one must not derive any assurance that perception will turn out to be true from a preconceived faith in Protagoreanism. 1 The criticism of Protagoras, then, aims to eliminate his views as an independent source of support for Theaetetus’ definition of knowledge.
