But, even if the _Sisyphus_ fragment cannot be used to characterise its author as an atheist, it is, nevertheless, of the greatest interest in this connexion, and therefore demands closer analysis.
The introductory idea, that mankind has evolved from an animal state into higher stages, is at variance with the earlier Greek conception, namely, that history begins with a golden age from which there is a continual decline. The theory of the fragment is expressed by a series of authors from the same and the immediately succeeding period. It occurs in Euripides; a later and otherwise little-known tragedian, Moschion, developed it in detail in a still extant fragment; Plato accepted it and made it the basis of his presentation of the origin of the State; Aristotle takes it for granted. Its source, too, has been demonstrated: it was presumably Democritus who first advanced it. Nevertheless the author of the fragment has hardly got it direct from Democritus, who at this time was little known at Athens, but from an intermediary. This intermediary is probably Protagoras, of whom it is said that he composed a treatise, _The Original State, i.e._ the primary state of mankind. Protagoras was a fellow-townsman of Democritus, and recorded by tradition as one of his direct disciples.
In another point also the fragment seems to betray the influence of Democritus. When it is said that the wise inventors of the gods made them dwell in the skies, because from the skies come those natural phenomena which frighten men, it is highly suggestive of Democritus’s criticism of the divine explanation of thunder and lightning and the like. In this case also Protagoras may have been the intermediary. In his work on the gods he had every opportunity of discussing the question in detail. But here we have the theory of Democritus combined with that of Prodicus in that it is maintained that from the skies come also those things that benefit men, and that they are on this account also a suitable dwelling-place for the gods. It is obvious that the author of the fragment (or his source) was versed in the most modern wisdom.
All this erudition, however, is made to serve a certain tendency: the well-known tendency to represent religion as a political invention having as its object the policing of society. It is a theory which in antiquity—to its honour be it said—is but of rare occurrence. There is a vague indication of it in Euripides, a more definite one in Aristotle, and an elaborate application of it in Polybius; and that is in reality all. (That many people in more enlightened ages upheld religion as a means of keeping the masses in check, is a different matter.) However, it is an interesting fact that the Critias fragment is not only the first evidence of the existence of the theory known to us, but also presumably the earliest and probably the best known to later antiquity. Otherwise we should not find reference for the theory made to a fragment of a farce, but to a quotation from a philosopher.