Note 2 — Chapter V · LIFE OF PLATO.
Reading edition
Diogen. Laert. iv. 1. The person to whom Diogenes addressed his biography of Plato was a female: possibly the wife of the emperor Septimius Severus (see Philostr. Vit. Apoll. i. 3), who greatly loved and valued the Platonic philosophy (Diog. Laert. iii. 47). Ménage (in his commentary on the Proœmium) supposes the person signified to be Arria: this also is a mere conjecture, and in my judgment less probable. We know that the empress gave positive encouragement to writers on philosophy. The article devoted by Diogenes to Plato is of considerable length, including both biography and exposition of doctrine. He makes reference to numerous witnesses — Speusippus, Aristotle, Hermodôrus, Aristippus, Dikæarchus, Aristoxenus, Klearchus, Herakleides, Theopompus, Timon in his Silli or satirical poem, Pamphila, Hermippus, Neanthes, Antileon, Favorinus, Athenodôrus. Timotheus, Idomeneus, Alexander ἐν διαδοχαῖς καθ’ Ἡράκλειτον, Satyrus, Onêtor, Alkimus, Euphorion, Panætius, Myronianus, Polemon, Aristophanes of Byzantium, the Alexandrine critic, Antigonus of Karystus, Thrasyllus, &c.
Of the other biographers of Plato, Olympiodorus and the Auctor Anonymus cite no authorities. Apuleius, in his survey of the doctrine of Plato (De Habitudine doctrinarum Platonis, init. p. 567, ed. Paris), mentions only Speusippus, as having attested the early diligence and quick apprehension of Plato. “Speusippus, domesticis instructus documentis, et pueri ejus acre in percipiendo ingenium, et admirandæ verecundiæ indolem laudat, et pubescentis primitias labore atque amore studendi imbutas refert,” &c.
Speusippus had composed a funeral Discourse or Encomium on Plato (Diogen. iii. 1, 2; iv. 1, 11). Unfortunately Diogenes refers to it only once in reference to Plato. We can hardly make out whether any of the authors, whom he cites, had made the life of Plato a subject of attentive study. Hermodôrus is cited by Simplikius as having written a treatise περὶ Πλάτωνος. Aristoxenus, Dikæarchus, and Theopompus — perhaps also Hermippus, and Klearchus — had good means of information.
See K. F. Hermann, Geschichte und System der Platonischen Philosophie, p. 97, not. 45.