22 DOGMATISM AND EVOLUTION 



sensation. A partial solution of the difficulty he found in the 

 example of geometry. Without sensible diagrams the geometri- 

 cian could accomplish little, and yet the most exquisitely con- 

 structed diagram was far from conforming to the exact require- 

 ments of the science. It was evidently as a suggestion that the 

 diagram was useful, a suggestion of a perfect prototype which 

 it weakly imitated. Was this not true of all our scientific ideas, 

 including those of morality and statecraft (in which Plato was 

 most deeply interested)? Is not the good man whom we see 

 brave, wise, temperate, and just as he may be a very imperfect 

 illustration of the ideal courage, wisdom, temperance, and justice 

 of which we can conceive, and of which the philosopher attempts 

 to frame adequate definitions? But if the conceptions of the 

 mathematical and moral sciences are not logically derived from 

 sense-impressions, but only suggested by them, what logical 

 ground have they? It seems to have been properly held by the 

 geometricians, that the fundamental conceptions of their science 

 were self-evident and needed no further warrant. But Plato saw 

 that this was not so. He perceived that all these conceptions 

 involved assumptions that might perfectly well be questioned 

 and that the geometricians had no way of defending; and he 

 believed the like to be true of the moral sciences. 



In order properly to found both classes of sciences, one must, 

 he thought, adopt a course directly the reverse of deduction. 

 Frankly recognizing their fundamental assumptions as mere hy- 

 potheses, one must seek for more comprehensive hypotheses 

 which shall unite and explain the former. And the new hypothe- 

 ses must be similarly treated ; and the process must be repeated 

 again and again until it is no longer necessary or possible. That 

 is to say, the process must be repeated until a conception is 

 reached which is no longer hypothetical, but which is indeed 

 self-explanatory and capable of explaining and justifying all the 

 conceptions that have led up to it. The content of this highest 

 conception Plato called the Good; and because the conception 

 was itself incapable of being explained in simpler terms, but 



