As it comes substantially from Theophrastos, this passage is to be regarded as good evidence for the cosmology of Leukippos, and it is confirmed in an interesting way by certain Epicurean extracts from the _Great Diakosmos_.[949] These, however, as is natural, give a specially Epicurean turn to some of the doctrines, and must therefore be used with caution. Footnote 949: These are to be found in Aet. i. 4 (_Dox._ p. 289; _Vors._ p. 347; Usener, _Epicurea_, fr. 308). Epicurus himself in the second epistle (Diog. x. 88; Usener, p. 37, 7) quotes the phrase ἀποτομὴν ἔχουσα ἀπὸ τοῦ ἀπείρου. [Sidenote: Relation to Ionic cosmology.] 177. The general impression which we get from the cosmology of Leukippos is that he either ignored or had never heard of the great advance in the general view of the world which was due to the later Pythagoreans. He is as reactionary in his detailed cosmology as he was daring in his general physical theory. We seem to be reading once more of the speculations of Anaximenes or even of Anaximander, though there are traces of Empedokles and Anaxagoras too. The explanation is not hard to see. Leukippos would not learn a cosmology from his Eleatic teachers; and, even when he found it possible to construct one without giving up the Parmenidean view of reality, he was necessarily thrown back upon the older systems of Ionia. The result was unfortunate. The astronomy of Demokritos, so far as we know it, was still of this childish character. There is no reason to doubt the statement of Seneca that he did not venture to say how many planets there were.[950] Footnote 950: Seneca, _Q. Nat._ vii. 3. This, I take it, is what gives plausibility to Gomperz’s statement that Atomism was “the ripe fruit on the tree of the old Ionic doctrine of matter which had been tended by the Ionian physiologists.”[951] The detailed cosmology was certainly such a fruit, and it was possibly over-ripe; but the atomic theory proper, in which the real greatness of Leukippos comes out, was wholly Eleatic in its origin. Nevertheless, it will repay us to examine the cosmology too; for such an examination will serve better than anything else to bring out the true nature of the historical development of which it was the outcome. Footnote 951: Gomperz, _Greek Thinkers_, vol. i. p. 323. [Sidenote: The eternal motion.]