This remark is not less applicable to Eukleides than to Plato, both of them agreeing in the doctrine here criticised. Zeller says truly, that the attempt to identify Unum and Bonum produces perpetual confusion. The two notions are thoroughly distinct and independent. It ought not to be called (as he phrases it) “a generalization of Bonum”. There is no common property on which to found a generalization. It is a forced conjunction between two disparates.
Last doctrine of Plato nearly the same as that of Eukleides.
This last doctrine of Plato in his later years (which does not appear in the dialogues, but seems, as far as we can make out, to have been delivered substantially in his oral lectures, and is ascribed to him by Aristotle) was nearly coincident with that of Eukleides. Both held the identity of τὸ ἕν with τὸ ἀγαθόν. This one doctrine is all that we know about Eukleides: what consequences he derived from it, or whether any, we do not know. But Plato combined, with this transcendental Unum = Bonum, a transcendental indeterminate plurality: from which combination he considered his Ideas or Ideal Numbers to be derivatives.
Megaric succession of philosophers. Eleian or Eritrean succession.
Eukleides is said to have composed six dialogues, the titles of which alone remain. The scanty information which we possess respecting him relates altogether to his negative logical procedure. Whether he deduced any consequences from his positive doctrine of the Transcendental Ens, Unum, Bonum, we do not know: but he, as Zeno had been before him,[25] was acute in exposing contradictions and difficulties in the positive doctrines of opponents. He was a citizen of Megara, where he is said to have harboured Plato and the other companions of Sokrates, when they retired for a time from Athens after the death of Sokrates. Living there as a teacher or debater on philosophy, he founded a school or succession of philosophers who were denominated Megarici. The title is as old as Aristotle, who both names them and criticises their doctrines.[26] None of their compositions are preserved. The earliest who becomes known to us is Eubulides, the contemporary and opponent of Aristotle; next Ichthyas, Apollonius, Diodôrus Kronus, Stilpon, Alexinus, between 340-260 B.C.
[25] Plato, Parmenides, p. 128 C, where Zeno represents himself as taking for his premisses the conclusions of opponents, to show that they led to absurd consequences. This seems what is meant, when Diogenes says about Eukleides — ταῖς ἀποδείξεσιν ἐνίστατο οὐ κατὰ λήμματα, ἀλλὰ κατ’ ἐπιφοράν (ii. 107); Deycks, De Megaricorum Doctrinâ, p. 34.
[26] Aristot. Metaph. iv. p. 1046, b. 29.
The sarcasm ascribed to Diogenes the Cynic implies that Eukleides was really known as the founder of a school — καὶ τὴν μὲν Εὐκλείδου σχολὴν ἔλεγε χολήν (Diog. L. vi. 24) — the earliest mention (I apprehend) of the word σχολὴ in that sense.
With the Megaric philosophers there soon become confounded another succession, called Eleian or Eretrian, who trace their origin to another Sokratic man — Phædon. The chief Eretrians made known to us are Pleistanus, Menedêmus, Asklepiades. The second of the three acquired some reputation.
Doctrines of Antisthenes and Aristippus — Ethical, not transcendental.