Protagoras is the only one of the sophists of whom tradition says that he was the object of persecution owing to his religious views. The trial of Socrates, however, really belongs to the same category when looked at from the accusers’ point of view; Socrates was accused as a sophist. But as his own attitude towards popular religion differed essentially from that of the sophists, we cannot consider him in this connexion. Protagoras’s trial itself is partly determined by special circumstances. In all probability it took place at a moment when a violent religious reaction had set in at Athens owing to some grave offences against the public worship and sanctuaries of the State (violation of the Mysteries and mutilation of the Hermae). The work on the gods had presumably been in existence and known long before this without causing scandal to anybody. But, nevertheless, the trial, like those of Anaxagoras and Socrates, plainly bears witness to the animosity with which the modern free-thought was regarded in Athens. This animosity did not easily manifest itself publicly without special reasons; but it was always there and might always be used in case of provocation. As to Protagoras’s personal attitude to the question of the existence of the gods, much may be guessed and much has been guessed; but nothing can be stated for certain. However, judging from the man’s profession and his general habit of life as it appears in tradition, we may take for granted that he did not give offence in his outward behaviour by taking a hostile attitude to public worship or attacking its foundations; had that been so, he would not for forty years have been the most distinguished teacher of Hellas, but would simply not have been tolerated. An eminent modern scholar has therefore advanced the conjecture that Protagoras distinguished between belief and knowledge, and that his work on the gods only aimed at showing that the existence of the gods could not be scientifically demonstrated. Now such a distinction probably, if conceived as a conscious principle, is alien to ancient thought, at any rate at the time of Protagoras; and yet it may contain a grain of truth. When it is borne in mind that the incriminated passage represents the very exordium of the work of Protagoras, the impression cannot be avoided that he himself did not intend his work to disturb the established religion, but that he quite naïvely took up the existence of the gods as a subject, as good as any other, for dialectic discussion. All that he was concerned with was theory and theorising; religion was practice and ritual; and he had no more intention of interfering with that than the other earlier sophists of assailing the legal system of the community in their speculation as to relativity of right and wrong.