On this question, then, of the Canon of Plato’s works (as compared with the works of other contemporary authors) recognised by Thrasyllus — I consider that its claim to trustworthiness is very high, as including all the genuine works, and none but the genuine works, of Plato: the following facts being either proved, or fairly presumable.
1. The Canon rests on the authority of the Alexandrine library and its erudite librarians;[54] whose written records went back to the days of Ptolemy Soter, and Demetrius Phalereus, within a generation after the death of Plato.
2. The manuscripts of Plato at his death were preserved in the school which he founded; where they continued for more than thirty years under the care of Speusippus and Xenokrates, who possessed personal knowledge of all that Plato had really written. After Xenokrates, they came under the care of Polemon and the succeeding Scholarchs, from whom Demetrius Phalereus probably obtained permission to take copies of them for the nascent museum or library at Alexandria or through whom at least (if he purchased from booksellers) he could easily ascertain which were Plato’s works, and which, if any, were spurious.
3. They were received into that library without any known canonical order, prescribed system, or interdependence essential to their being properly understood. Kallimachus or Aristophanes devised an order of arrangement for themselves, such as they thought suitable.
[54] Suckow adopts and defends the opinion here stated — that Thrasyllus, in determining which were the genuine works of Plato and which were not genuine, was guided mainly by the authority of the Alexandrine library and librarians (G. F. W. Suckow, Form der Platonischen Schriften, pp. 170-175). Ueberweg admits this opinion as just (Untersuchungen, p. 195).
Suckow farther considers (p. 175) that the catalogue of works of esteemed authors, deposited in the Alexandrine library, may be regarded as dating from the Πίνακες of Kallimachus.
This goes far to make out the presumption which I have endeavoured to establish in favour of the Canon recognised by Thrasyllus, which, however, these two authors do not fully admit.
K. F. Hermann, too (see Gesch. und Syst. der Platon. Philos. p. 44), argues sometimes strongly in favour of this presumption, though elsewhere he entirely departs from it.