86 THE GREEK SCHOOL PHILOSOPHY. 



namely, the Idea of Mechanical Cause, which is 

 Force; and the substitution of vague or inappli- 

 cable notions involving only relations of space, or 

 emotions of wonder. The errors of those who failed 

 similarly in other instances, were of the same kind. 

 To detail or classify these would lead us too far into 

 the philosophy of science ; since we should have to 

 enumerate the Ideas which are appropriate, and the 

 various class of Facts on which the different sciences 

 are founded, a task not to be now lightly under- 

 taken. But it will be perceived, without further 

 explanation, that it is necessary, in order to obtain 

 from facts any general truth, that we should apply 

 to them that appropriate Idea, by which permanent 

 and definite relations are established among them. 



In such ideas the ancients were very poor, and 

 the stunted and deformed growth of their physical 

 science was the result of this penury. The Ideas of 

 Space and Time, Number and Motion, they did in- 

 deed possess distinctly ; and so far as these went, 

 their science was tolerably healthy. They also 

 caught a glimpse of the Idea of a Medium by which 

 the qualities of bodies, as colours and sounds, are 

 perceived. But the idea of Substance remained 

 barren in their hands; in speculating about elements 

 and qualities, they went the wrong way, assuming 

 that the properties of the Compounds must resemble 

 those of the Elements which determine them ; and 

 their loose notions of Contrariety never approached 

 the form of those ideas of Polarity, which, in mo- 



