CLASSIFICATION OF THE SCIENCES. 



in a semi-circle is a right angle abstract in the sense 

 that though it does not hold in actually-constructed 

 semi-circles and angles, which are always inexact, it 

 holds in the ideal semi-circles and angles abstracted 

 from real ones ; but this is not a general truth, either 

 in the sense that it is commonly manifested in Nature, 

 or in the sense that it is a space-relation that compre 

 hends many minor space-relations : it is a quite 

 special space-relation. Again, that the momentum 

 of a body causes it to move in a straight line at a 

 uniform velocity, is an abstract-concrete truth a 

 truth abstracted from certain experiences of concrete 

 phenomena ; but it is by no means a general truth : 

 so little generality has it, that no one fact in Kature 

 displays it. Conversely, surrounding things supply 

 us with hosts of general truths that are not in the 

 least abstract. It is a general truth that the planets 

 go round the Sun from West to East a truth which 

 holds good in something like a hundred cases (includ 

 ing the cases of the planetoids) ; but this truth 

 is not at all abstract, since it is perfectly realized 

 as a concrete fact in every one of these cases. Every 

 vertebrate animal whatever, has a double nervous 

 system ; all birds and all mammals are warm 

 blooded these are general truths, but they are 

 concrete truths : that is to say, every vertebrate 

 animal individually presents an entire and unqualified 

 manifestation of this duality of the nervous system ; 

 every living bird exemplifies absolutely or completely 



