90 THE GREEK SCHOOL PHILOSOPHY. 



in speculating about elements and qualities, they went the wrong- way 

 assuming that the properties of 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 mod- 

 ern times, regulate many parts of physics and chemistry. 



If this statement should seem to any one to be technical or arbi- 

 trary, we must refer, for the justification of it, Ho the Philosophy oi 

 Science, of which we hope hereafter to treat. But it will appear, 

 even from what has been here said, that there are certain Ideas or 

 Forms of mental apprehension, which may be applied to Facts in such 

 a manner as to bring into view fundamental principles of science ; 

 while the same Facts, however arrayed or reasoned about, so long as 

 these appropriate ideas are not employed, cannot give rise to any 

 exact or substantial knowledge. 



[2d Ed.] This account of the cause of failure in the physical specu- 

 lations of the ancient Greek philosophers has been objected to as un 

 satisfactory. I will offer a few words in explanation of it. 



The mode of accounting for the failure of the Greeks in physics is, 

 in substance ; that the Greeks in their physical speculations fixed theii 

 attention upon the wrong aspects and relations of the phenomena ; 

 and that the aspects and relations in which phenomena are to be 

 viewed in order to arrive at scientific truths may be arranged under 

 certain heads, which I have termed Ideas; such as Space, Time, 

 Number, Cause, Likeness. In every case, there is an Idea to which 

 the phenomena may be referred, so as to bring into view the Laws by 

 which they are governed ; this Idea I term the appropriate Idea in 

 such case ; and in order that the reference of the phenomena to the 

 Law may be clearly seen, the Idea must be distinctly possessed. 



Thus the reason of Aristotle's failure in his attempts at Mechanical 

 Science is, that he did not refer the facts to the appropriate Idea, 

 namely Force, the Cause of Motion, but to relations of Space and the 

 like ; that is, he introduces Geometrical instead of Mechanical Ideas. 

 It may be said that we learn little by being told that Aristotle's 

 failure in this and the like cases arose from his referring to the wrong 

 class of Ideas ; or, as I have otherwise expressed it, fixing his attention 

 upon the wrong aspects and relations of the facts ; since, it may be 

 said, this is only to state in other words that he did fail. But this 

 criticism is, I think, ill-founded. The account which I have given is 

 not only a statement that Aristotle, and others who took a like course, 

 did fail ; but also, that they failed in one certain point out of several 



