There are some, again, who, though they do not suppose that this world is eternal, are of opinion either that this is not the only world, but that there are numberless worlds, or that indeed it is the only one, but that it dies, and is born again at fixed intervals, and this times without number; but they must acknowledge that the human race existed before there were other men to beget them. For they cannot suppose that, if the whole world perish, some men would be left alive in the world, as they might survive in floods and conflagrations, which those other speculators suppose to be partial, and from which they can therefore reasonably argue that a few men survived whose posterity would renew the population; but as they believe that the world itself is renewed out of its own material, so they must believe that out of its elements the human race was produced, and then that the progeny of mortals sprang like that of other animals from their parents.