Note 24 — Chapter V · LIFE OF PLATO.

For an account of Eudoxus himself, of his theory of concentric spheres, and the subsequent extensions of it, see the instructive volume of the late lamented Sir George Cornewall Lewis, — Historical Survey of the Ancient Astronomy, ch. iii. sect. 3, p. 146 seq.

M. Boeckh also (in his recent publication, Ueber die vierjährigen Sonnenkreise der Alten, vorzüglich den Eudoxischen, Berlin, 1863) has given an account of the life and career of Eudoxus, not with reference to his theory of concentric spheres, but to his Calendar and Lunisolar Cycles or Periods, quadrennial and octennial. I think Boeckh is right in placing the voyage of Eudoxus to Egypt at an earlier period of the life of Eudoxus; that is, about 378 B.C.; and not in 362 B.C., where it is placed by Letronne and others. Boeckh shows that the letters of recommendation from Agesilaus to Nektanebos, which Eudoxus took with him, do not necessarily coincide in time with the military expedition of Agesilaus to Egypt, but were more probably of earlier date. (Boeckh, p. 140-148.)

Eudoxus lived 53 years (406-353 B.C., about); being born when Plato was 21, and dying when Plato was 75. He was one of the most illustrious men of the age. He was born in poor circumstances; but so marked was his early promise, that some of the medical school at Knidus assisted him to prosecute his studies — to visit Athens and hear the Sophists, Plato among them — to visit Egypt, Tarentum (where he studied geometry with Archytas), and Sicily (where he studied τὰ ἰατρικὰ with Philistion). These facts depend upon the Πίνακες of Kallimachus, which are good authority. (Diog. L. viii. 86.)

After thus preparing himself by travelling and varied study, Eudoxus took up the profession of a Sophist, at Kyzikus and the neighbouring cities in the Propontis. He obtained great celebrity, and a large number of pupils. M. Boeckh says, “Dort lebte er als Sophist, sagt Sotion: das heisst, er lehrte, und hielt Vortrage. Dasselbe bezeugt Philostratos.”

I wish to call particular attention to the way in which M. Boeckh here describes a Sophist of the fourth century B.C. Nothing can be more correct. Every man who taught and gave lectures to audiences more or less numerous, was so called. The Platonic critics altogether darken the history of philosophy, by using the word Sophist with its modern associations (and the unmeaning abstract Sophistic which they derive from it), to represent a supposed school of speculative and deceptive corruptors.

Eudoxus, having been coldly received when young and poor by Plato, had satisfaction in revisiting Athens at the height of his reputation, accompanied by numerous pupils — and in showing himself again to Plato. The two then became friends. Menæchmus and Helikon, geometrical pupils of Eudoxus, received instruction from Plato also; and Helikon accompanied Plato on his third voyage to Sicily (Plato, Epist. xiii. p. 360 D; Plut. Dion, c. 19). Whether Eudoxus accompanied him there also, as Boeckh supposes, is doubtful: I think it improbable.

Eudoxus ultimately returned to his native city of Knidus, where he was received with every demonstration of honour: a public vote of esteem and recognition being passed to welcome him. He is said to have been solicited to give laws to the city, and to have actually done so: how far this may be true, we cannot say. He also visited the neighbouring prince Mausôlus of Karia, by whom he was much honoured.

We know from Aristotle, that Eudoxus was not only illustrious as an astronomer and geometer, but that he also proposed a theory of Ethics, similar in its general formula to that which was afterwards laid down by Epikurus. Aristotle dissents from the theory, but he bears express testimony, in a manner very unusual with him, to the distinguished personal merit and virtue of Eudoxus (Ethic. Nikom. x. 3, p. 1172, b. 16).