2. An Athenian, the son of Euphronius of Sunium, is introduced as one of the speakers in Plato's Theaeteius and Sophistes, in which dialogues he is spoken of as a noble, courageous, and well-disposed youth; in person somewhat like Socrates ; and ardent in the pursuit of knowledge, especially in the study of geometry. (Plat. Theaet. pp. 143, 144. et alib.; Sophist. passim; Polit. pp. 257, 258, p. 266a.) Diogenes Laertius (2.29) mentions him as an example of the happy effects of the teaching of Socrates. Eusebius (Chron.) places "Theaetetus the mathematician" at Ol. 85, B. C. 440, a date which can only be accepted as referring, not to the time when he really flourished, but when, as a mere youth, he became the disciple of Socrates. (Comp. Fabric. Bibl. Graec. vol. iii. p. 78, note.)