"bodies", and is still sensible knowledge; corresponding to the 

 third process of knowledge are mathematical objects, but because 

 mathematics does not dispense entirely with the data of sense or 

 with hypothesis, it is not the highest study ; it cannot be reckoned as 

 true philosophy, for the objects corresponding to eTrio-Tij/w; or pure 

 knowledge are quite beyond the realm of sense. These objects are 

 called by Plato 'I5ecu. They are the Ideas. 



And now it is time to ask what these Ideas are with which 

 Plato's philosophers are to become busied. True knowledge for 

 Plato consisted, it seems, in the contemplation of these Ideas, and 

 these, whatever else they may be, are regarded as having no sense- 

 content. Surely, it is objected, this is diametrically opposed to 

 modern science, since, for modern science, that which is given in 

 sense-experience is of the utmost value, while, for Plato, it would 

 seem, all such counts as a hindrance and a barrier to the higher 

 knowledge. But before it can be agreed that Plato's conception 

 of science differs so widely from that of to-day, it must be deter- 

 mined more clearly what is meant by the word Idea, and what 

 significance there is in Plato's doctrine of Ideas. 



The following passage from the Metaphysics XIII, 1078 b 9 pre- 

 sents Aristotle's view of Plato's theory. "Now regarding the 

 Ideas, we must first examine the Ideal theory (theory of Ideas) 

 by itself not connecting it in any way with the nature of numbers 

 but treating it in the form in which it was originally, understood 

 by those who first maintained the existence of Ideas. The sup- 

 porters of the Ideal theory were led to it because they were per- 

 suaded of the truth of the Heraclitean doctrine that all sensible 

 things are ever passing away, so that, if knowledge or thought is 

 to have an object, there must be some other abiding and permanent 

 entities, apart from those which are sensible; for there can be no 

 knowledge of things which are in a state of flux. Socrates occupied 

 himself with the excellencies of character, and, in connection with 

 them became the first to raisethe problem of universal definitions. 

 .... For two things may be fairly ascribed to Socrates in- 

 ductive arguments and universal definition, both of which are 

 concerned with the starting-point of science. But Socrates did 

 not make the universals or the definitions exist apart ; his successors, 

 however, gave them separate existence, and this was the kind of 



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