In Callicles an attempt has been made to see a pseudonym for Critias. That is certainly wrong. Critias was a kinsman of Plato, is introduced by name in several dialogues, nay, one dialogue even bears his name, and he is everywhere treated with respect and sympathy. Nowadays, therefore, it is generally acknowledged that Callicles is a real person, merely unknown to us as such. However that may be, Plato would never have let a leading character in one of his longer dialogues advance (and Socrates refute) a view which had no better authority than a passage in a satyric drama. On the other hand, there is, as shown above, difficulty in supposing that the doctrine of the fragment was stated in the writings of an eminent sophist; so we come to the conclusion that it was developed and diffused in sophistic circles by oral teaching, and that it became known to Critias and Plato in this way. Its originator we do not know. We might think of the sophist Thrasymachus, who in the first book of Plato’s _Republic_ maintains a point of view corresponding to that of Callicles in _Gorgias_. But what we otherwise learn of Thrasymachus is not suggestive of interest in religion, and the only statement of his as to that kind of thing which has come down to us tends to the denial of a providence, not denial of the gods. Quite recently Diagoras of Melos has been guessed at; this is empty talk, resulting at best in substituting _x_ (or _NN_) for _y_. If I have dwelt in such detail on the _Sisyphus_ fragment, it is because it is our first direct and unmistakable evidence of ancient atheism. Here for the first time we meet with the direct statement which we have searched for in vain among all the preceding authors: that the gods of popular belief are fabrication pure and simple and without any corresponding reality, however remote. The nature of our tradition precludes our ascertaining whether such a statement might have been made earlier; but the probability is _a priori_ that it was not. The whole development of ancient reasoning on religious questions, as far as we are able to survey it, leads in reality to the conclusion that atheism as an expressed (though perhaps not publicly expressed) confession of faith did not appear till the age of the sophists. With the Critias fragment we have also brought to an end the inquiry into the direct statements of atheistic tendency which have come down to us from the age of the sophists. The result is, as we see, rather meagre. But it may be supplemented with indirect testimonies which prove that there was more of the thing than the direct tradition would lead us to conjecture, and that the denial of the existence of the gods must have penetrated very wide circles.