In Schol. p. 573, a. 18, it is stated that the astronomer Eudoxus was a hearer both of Plato and of Eukleides. The account given by Zeller (Phil. der Griech. ii. p. 453, 2nd ed.) of this latter phase of the Platonic doctrine of Ideas, applies exactly to that which we hear about the main doctrine of Eukleides. Zeller describes the Platonic doctrine as being "Eine Vermischung des ethischen Begriffes vom höchsten Gut, mit dem Metaphysischen des Absoluten: Der Begriff des Guten ist zunächst aus dem menschlichen Leben abstrahirt; er bezeichnet das, was dem Menschen zuträglich ist. So noch bei Sokrates. Plato verallgemeinert ihn nun zum Begriff des Absoluten; dabei spielt aber seine ursprüngliche Bedeutung noch fortwährend herein, und so entsteht die Unklarheit, dass weder der ethische noch der metaphysische Begriff des Guten rein gefasst wird." 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.] [Side-note: 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 [Greek: to\ e(/n] with [Greek: to\ a)gatho/n]. 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. [Side-note: Megaric succession of philosophers. Eleian or Eritrean succession.]