Theon of Smyrna: Book on Astronomy

to the authors he himself uses, namely Thrasyllus the Platonist, who lived under Augustus and Tiberius1, and Adrastus the Peripatetic, who must be thought to have lived after Thrasyllus2. Nor is he posterior to Proclus, who criticizes him for being inconsistent3, or Chalcidius, who, living at the end of the fifth century, used his Astronomy—very ineptly, to be sure, but very evidently4. Indeed, it does not seem credible that Theon of Smyrna lived after Ptolemy: for while he is accustomed to indicate his sources, and while he happens to use the same criticisms against the errors of Aristoxenus regarding the division of the tone5 that Ptolemy explained at length in his Harmonics6, he is entirely silent about Ptolemy’s Harmonics7; and while knowing most of the things discovered in astronomical science by Hipparchus and thereafter up to the time of Ptolemy, he is thoroughly ignorant of those things which Ptolemy added of his own, and nowhere in his astronomical work does he appeal to Ptolemy8. Therefore, Theon of Smyrna was either a contemporary of Ptolemy, who flourished roughly in the middle of the second century after the birth of Christ, or was slightly anterior to him.

An ancient likeness of Theon of Smyrna, after Spon9...

1 See Part II, ch. III, § 13 of this dissertation.
2 Ibid., § 15.
3 In Timaeus, p. 26 A (Greek ed. Basel), p. 58 (Schneider).
4 See Part I, ch. I, § 5 of this dissertation.
5 Theon of Smyrna, Music, ch. VIII, pp. 83-84 (Bullialdus edition).
6 I, 10.
7 Cf. Bullialdus, To the Reader, p. 8.
8 See Part II, ch. III; and ch. IV, § 15 of this dissertation.
9 Miscellanea IV, p. 135.