134 NAMES AND PROPOSITIONS. 



Is there no difference, then, save this merely verbal one, 

 between the classes which the schoolmen admitted to be genera 

 or species, and those to which they refused the title ? Is it 

 an error to regard some of the differences which exist among 

 objects as differences in kind (genere or specie], and others only 

 as differences in the accidents ? Were the schoolmen right or 

 wrong in giving to some of the classes into which things may 

 be divided, the name of kinds, and considering others as 

 secondary divisions, grounded on differences of a comparatively 

 superficial nature ? Examination will show that the Aristo- 

 telians did mean something by this distinction, and some- 

 thing important ; but which, being but indistinctly conceived, 

 was inadequately expressed by the phraseology of essences, 

 and the various other modes of speech to which they had 

 recourse. 



4. It is a fundamental principle in logic, that the 

 power of framing classes is unlimited, as long as there is 

 any (even the smallest) difference to found a distinction 

 upon. Take any attribute whatever, and if some things have 

 it, and others have not, we may ground on the attribute a 

 division of all things into two classes ; and we actually do so, 

 the moment we create a name which connotes the attribute. 

 The number of possible classes, therefore, is boundless ; and 

 there are as many actual classes (either of real or of imaginary 

 things) as there are general names, positive and negative to- 

 gether. 



But if we contemplate any one of the classes so formed, 

 such as the class animal or plant, or the class sulphur or phos- 

 phorus, or the class white or red, and consider in what parti- 

 culars the individuals included in the class differ from those 

 which do not come within it, we find a very remarkable diver- 

 sity in this respect between some classes and others. There 

 are some classes, the things contained in which differ from 

 other things only in certain particulars which may be num- 

 bered, while others differ in more than can be numbered, more 

 even than we need ever expect to know. Some classes have 

 little or nothing in common to characterize them by, except 



