_Phys._ Γ, 8. 208 a 8 (R. P. 16 a). That this refers to Anaximander is shown by Aet. i. 3, 3 (R. P. 16 a). The same argument is given in _Phys._ Γ, 4. 203 b 18, a passage where Anaximander has just been quoted by name, τῷ οὕτως ἂν μόνον μὴ ὑπολείπειν γένεσιν καὶ φθοράν, εἰ ἄπειρον εἴη ὅθεν ἀφαιρεῖται τὸ γιγνόμενον. I cannot, however, believe that the arguments given at the beginning of this chapter (203 b 7; R. P. 17) are Anaximander’s. They bear the stamp of the Eleatic dialectic, and are, in fact, those of Melissos. Footnote 114: I have assumed that the word ἄπειρον means _spatially infinite_ (though not in any precise mathematical sense), not _qualitatively indeterminate_, as maintained by Teichmüller and Tannery. The decisive reasons for holding that the sense of the word is “boundless in extent” are as follows: (1) Theophrastos said that the primary substance of Anaximander was ἄπειρον and contained all the worlds, and the word περιέχειν everywhere means “to encompass,” not, as has been suggested, “to contain potentially.” (2) Aristotle says (_Phys._ Γ, 4. 203 b 23) διὰ γὰρ τὸ ἐν τῇ νοήσει μὴ ὑπολείπειν καὶ ὁ ἀριθμὸς δοκεῖ ἄπειρος εἶναι καὶ τὰ μαθηματικὰ μεγέθη καὶ τὰ ἔξω τοῦ οὐρανοῦ· ἀπείρου δ’ ὄντος τοῦ ἔξω, καὶ σῶμα ἄπειρον εἶναι δοκεῖ καὶ κόσμοι. (3) Anaximander’s theory of the ἄπειρον was adopted by Anaximenes, and he identified it with Air, which is not qualitatively indeterminate. [Sidenote: The eternal motion.] 17. The doxographers say it was the “eternal motion” that brought into being “all the heavens and all the worlds within them.” As we have seen (§ VIII), it is not likely that Anaximander himself used the phrase “eternal motion.” That is rather Aristotle’s own version of what he found stated about the “separating out” of opposites. We are not told expressly how Anaximander conceived this to operate, but the term “separating out” suggests some process of shaking and sifting as in a sieve. Now it is just such a process that Plato makes the Pythagorean Timaios describe, and the most probable theory is certainly that here, as in many other cases, he has reproduced a genuinely early view. As we shall see, it is quite likely that the Pythagoreans should have followed Anaximander in this.[115] In any case, it is wrong to identify the “eternal motion” with the diurnal revolution of the heavens, as has sometimes been done. That motion cannot possibly be eternal, for the simple reason that the heavens themselves are perishable. Aristotle says, indeed, that all who believe the world has come into being represent the earth as having been forced into the centre by the circular motion;[116] but, though this doubtless refers to Anaximander among others, it is quite irrelevant here. It has to do only with the formation of the world after it has been once for all separated off and enclosed in its own heaven, and we shall have to remember it when we come to that part of the theory.