a very important one, no doubt, among many. It has been already 

 mentioned, at the beginning of this chapter, that the word philoso- 

 phy was used in a dual sense by both Plato and Aristotle. The 

 word is used by each as a class-name, including under it all the 

 special studies which had arisen. But the significance generally 

 attached to the term is quite different from this. To consider 

 Plato first, the concluding sentence of the fifth book of the Re- 

 public defines as philosophers those "who set their affections on 

 that which in each case really exists." Now what does Plato mean 

 by that which in each case really exists? To understand the 

 answer to this question involves a statement of Plato's doctrine 

 of M Ideas ", which forms the very heart and centre of his system and 

 around which all else circulates. 



It will serve as an introduction to this theory of Ideas if there 

 be stated here that classification of knowledge, which Plato gives 

 in the sixth book of his master-work, the Republic. It has been 

 decided that at the head of the commonwealth there must be placed 

 men trained in philosophy. "There can be no cure for the ills of a 

 State or, as I think, of the whole human race, until political power 

 and philosophy are united, until either philosophers become kings 

 or those who are now called kings and potentates begin to pursue 

 philosophy not superficially but in the true spirit." 1 To describe 

 the training necessary for the philosopher-statesman, part of the 

 sixth and the whole of the seventh books are devoted. After the 

 study of mathematics, including arithmetic and geometry, and 

 astronomy there next comes the investigation of "that which in 

 each case really exists", or, as it is expressed, the students are now 

 prepared for the study of philosophy itself. According to the 

 scheme outlined by Plato there are four grades of knowledge, the 

 first or lowest is called ekao-ta, the next is Trio-m, the third 

 is .diavoia, while the highest of all is vorjaLs or e-Trtcrr^^- The 

 first two compose the realm of <5oa, opinion, and might be trans- 

 lated as conjecture and belief or conviction; d'.avoLa, under- 

 standing, reasoning through things, is not quite on the same level 

 as vo^ais or eTrio-rrjjuTy, which for Plato are synonymous with 

 Reason or pure knowledge. In conjecture, knowledge is of 

 "images" only, a mere guess-work; in belief, knowledge is of 



Rep. Bk. V. 



48 



