In the tenth book of his _Laws_, written shortly before his death, _i.e._ about the middle of the fourth century, Plato gives a detailed account of the question of irreligion seen from the point of view of penal legislation. He distinguishes here between three forms, namely, denial of the existence of the gods, denial of the divine providence (whereas the existence of the gods is admitted), and finally the assumption that the gods exist and exercise providence, but that they allow themselves to be influenced by sacrifices and prayers. Of these three categories the last is evidently directed against ancient popular belief itself; it does not therefore interest us in this connexion. The second view, the denial of a providence, we have already met with in Xenophon in the character of Aristodemus, and in the sophist Thrasymachus; Euripides, too, sometimes alludes to it, though it was far from being his own opinion. Whether it amounted to denial of the gods or not was, in ancient times, the cause of much dispute; it is, of course, not atheism in our sense, but it is certainly evidence that belief in the gods is shaken. The first view, on the other hand, is sheer atheism. Plato consequently reckons with this as a serious danger to the community; he mentions it as a widespread view among the youth of his time, and in his legislation he sentences to death those who fail to be converted. It would seem certain, therefore, that there was, in reality, something in it after all. Plato does not confine himself to defining atheism and laying down the penalty for it; he at the same time, in accordance with a principle which he generally follows in the _Laws_, discusses it and tries to disprove it. In this way he happens to give us information—which is of special interest to us—of the proofs which were adduced by its followers. The argument is a twofold one. First comes the naturalistic proof; the heavenly bodies, according to the general (and Plato’s own) view the most certain deities, are inanimate natural objects. It is interesting to note that in speaking of this doctrine in detail reference is clearly made to Anaxagoras; this confirms our afore-mentioned conjectures as to the character of his work. Plato was quite in a position to deal with Anaxagoras on the strength not only of what he said, but of what he passed over in silence. The second argument is the well-known sophistic one, that the gods are _nomôi_, not _physei_, they depend upon convention, which has nothing to do with reality. In this connexion the argument adds that what applies to the gods, applies also to right and wrong; _i.e._ we find here in the _Laws_ the view with which we are familiar from Callicles in the _Gorgias_, but with the missing link supplied. And Plato’s development of this theme shows clearly just what a general historical consideration might lead us to expect, namely, that it was naturalism and sophistic that jointly undermined the belief in the old gods. CHAPTER V