Abstract

In modern studies it has been largely denied that the so-called “secret doctrine” (which would be more correct to call “private teaching”) of the Theaetetus can be traced back to Protagoras. However, reasons why this doctrine can not be his own, have never been explained. At the same time, an appropriate justification of the hypothesis that it would be considered a pure Platonic creation has never been offered, nor was explained why it would be attributed to followers of Protagoras, but not to Protagoras himself. This article examines the Platonic text in an analytical way, shows how Plato repeatedly attributes to the sophist of Abdera the content of this doctrine, and, based on fragments of Protagoras and other doctrines related to him by ancient sources, it is evident that nothing in Protagorean concepts comes into conflict with Theaetetus so-called “secret doctrine”, and how actually is completely coherent with it.