At present, we have only to do with the motion of the Boundless itself; and, if we wish to picture that, it is much safer to regard it as a sort of shaking up and down which sorts out the opposites from the infinite mass. Footnote 115: Plato, _Tim._ 52 e, where the elements are separated by being shaken, stirred, and carried in different directions: “just as by sieves and instruments for winnowing corn, the grain is shaken and sifted, and the dense and heavy parts go one way, and the rare and light are carried to a different place and settle there.” For the relation of Pythagoreanism to Anaximander, see below, § 53. Footnote 116: Arist. _de Caelo_, Β, 13. 295 a 9. The identification of the eternal motion with the diurnal revolution is insisted on by Teichmüller and Tannery, and is the real source of the very unnatural interpretation which they give to the word ἄπειρον. It was obviously difficult to credit Anaximander with a belief in an infinite body which revolves in a circle. The whole theory rests upon a confusion between the finite spherical κόσμος within the οὐρανός and the infinite περιέχον outside it. [Sidenote: The innumerable worlds.] 18. We are told more than once that Anaximander believed there were “innumerable worlds in the Boundless,”[117] and it is now usual to regard these with Zeller as an infinite series succeeding one another in time. It may be allowed at once that his disproof of the idea that the worlds are coexistent and eternal is decisive. To suppose that Anaximander regarded this or any other world as eternal, is a flat contradiction of everything we otherwise know, and of the Theophrastean tradition that he taught the world was perishable. We have, then, to decide between the view that, though all the worlds are perishable, there may be an unlimited number of them in existence at the same time, and the view that a new world never comes into existence till the old one has passed away. Now, Zeller allows[118] that there is nothing in the first of these views that is inconsistent with what we know of Anaximander; but he thinks all the statements which have come down to us point rather to the second. It seems to me that this is by no means the case, and, as the matter is of fundamental importance, it will be necessary to examine the evidence once more. Footnote 117: [Plut.] _Strom._ fr. 2 (R. P. 21 b). The words ἀνακυκλουμένων πάντων αὐτῶν are most naturally to be interpreted as referring to an ἀνακύκλησις or cycle of γένεσις and φθορά in each of a multitude of coexistent worlds. It would be a very strange phrase to use of a succession of single worlds. Footnote 118: Zeller, pp. 234 sqq.