50 SCIENCE AND THE HUMAN MIND 



concrete objects of sense, Aristotle recognized also a 

 secondary reality in the universals or ideas, which 

 he held to exist in and with the objects of sense as 

 their essence. In later times this view was developed 

 into pure nominalism, according to which the indivi- 

 duals are the only realities, the universals being taken 

 merely as names, or mental concepts. To this ques- 

 tion we shall be brought back in dealing with mediaeval 

 thought. 



Now, whatever be the truth about Plato's doctrine 

 of ideas from a metaphysical or logical point of view 

 and in a modern form it is still held by many philo- 

 sophers the mental attitude which gave it birth is 

 not adapted to further the cause of experimental 

 science, before its exclusively logical or metaphysical 

 import is recognized. The school of Plato, including 

 even Aristotle, were far too prone to treat a scientific 

 problem under a preconception of the supreme import- 

 ance of words and their meanings, to consider that 

 hot is necessarily opposed to cold, heavy to light, 

 and to assume that bodies possessed essential qualities 

 corresponding to one or other of these contrasted 

 words. 



The characteristic weakness of the inductive sciences 

 among the Greeks is explicable when we examine their 

 theories of knowledge. Aristotle, while dealing skil- 

 fully with the theory of the process of passing from 

 particular instances of judgments of sense to general 

 propositions, regarded this induction merely as a 

 necessary preliminary to true science of the deductive 

 type, which, by logical reasoning, deduces conse- 

 quences from the premises reached by the former 

 process. 



