in the eighth book of his treatise on the World. But Chrysippus, in the first book of his essay on Providence, and Posidonius in his treatise on Gods, say that the heaven is the dominant principle of the world; and Cleanthes attributes this to the sun. Chrysippus, however, on this point contradicts himself; for he says in another place, that the most subtle portion of the æther, which is also called by the Stoics the first God, is what is infused in a sensible manner into all the beings which are in the air, and through every animal and every plant, and through the earth itself according to a certain habit; and that it is this which communicates to them the faculty of feeling.
They say too, that the world is one and also finite, having a spherical form. For that such a shape is the most convenient for motion, as Posidonius says, in the fifteenth book of his Discussions on Natural Philosophy, and so says Antipater also in his essay on the World. And on the outside there is diffused around it a boundless vacuum, which is incorporeal. And it is incorporeal inasmuch, as it is capable of being contained by bodies, but is not so. And that there is no such thing as a vacuum in the world, but that it is all closely united and compact; for that this condition is necessarily brought about by the concord and harmony which exist between the heavenly bodies and those of the earth. And Chrysippus mentions a vacuum in his essay on a Vacuum, and also in the first book of his treatise on the Physical Arts, and so does Apollophanes in his Natural Philosophy, and so does Apollodorus, and so does Posidonius in the second book of his discourses on Natural Philosophy. And they say that these things are all incorporeal, and all alike. Moreover, that time is incorporeal, since it is an interval of the motion of the world.