That Xenophanes was not considered an atheist by the ancients may possibly be explained by the fact that they objected to fasten this designation on a man whose reasoning took the deity as a starting-point and whose sole aim was to define its nature. Perhaps they also had an inkling that he in reality stood on the ground of popular belief, even if he went beyond it. Still more curious is the fact that his religious view does not seem to have influenced the immediately succeeding philosophy at all. His successors, Parmenides and Zeno, developed his doctrine of unity, but in a pantheistic direction, and on a logical, not religious line of argument; about their attitude to popular belief we are told practically nothing. And Ionic speculation took a quite different direction. Not till a century later, in Euripides, do we observe a distinct influence of his criticism of popular belief; but at that time other currents of opinion had intervened which are not dependent on Xenophanes, but might direct attention to him.
Ancient Greek naturalism is essentially calculated to collide with the popular belief. It seeks a natural explanation of the world, first and foremost of its origin, but in the next place of individual natural phenomena. As to the genesis of the world, speculations of a mythical kind had already developed on the basis of the popular belief. They were not, however, binding on anybody, and, above all, the idea of the gods having created the world was altogether alien to Greek religion. Thus, without offence to them it might be maintained that everything originated from a primary substance or from a mixture of several primary substances, as was generally maintained by the ancient naturalists. On the other hand, a conflict arose as soon as the heavenly phenomena, such as lightning and thunder, were ascribed to natural causes, or when the heavenly bodies were made out to be natural objects; for to the Greeks it was an established fact that Zeus sent lightning and thunder, and that the sun and the moon were gods. A refusal to believe in the latter was especially dangerous because they were _visible_ gods, and as to the person who did not believe in their divinity the obvious conclusion would be that he believed still less in the invisible gods.