CLASSIFICATION AND THE PKEDICABLES. 97 



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 differ- 

 ences 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, ground- 

 ed on differences of a comparatively superficial nature? Examination will 

 show that the Aristotelians did mean something by this distinction, and 

 something important; but which, being but indistinctly conceived, was in- 

 adequately 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, there- 

 fore, 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 phosphorus, or the class white or 

 red, and consider in what particulars the individuals included in the class 

 differ from those which do not come within it, we find a very remarkable 

 diversity in this respect between some classes and others. There are some 

 classes, the things contained in which differ from other things only in cer- 

 tain particulars which may be numbered, 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 

 precisely what is connoted by the name : white things, for example, are not 

 distinguished by any common properties except whiteness ; or if they are, 

 it is only by such as are in some way dependent on, or connected with, 

 whiteness. But a hundred generations have not exhausted the common 

 properties of animals or of plants, of sulphur or of phosphorus ; nor do we 

 suppose them to be exhaustible, but proceed to new observations and ex- 

 )eriments, in the full confidence of discovering new properties which were 

 )y no means implied in those we previously knew. While, if any one were 

 o propose for investigation the common properties of all things which are 

 )f the same color, the same shape, or the same specific gravity, the absurd- 

 ty would be palpable. We have no ground to believe that any such com- 

 non properties exist, except such as may be shown to be involved in the 

 ; upposition itself, or to be derivable from it by some law of causation. It 

 ; ppears, therefore, that the properties, on which we ground our classes, 

 i ometimes exhaust all that the class has in common, or contain it all by 

 .' ome mode of implication ; but in other instances we make a selection of a 

 \ 3W properties from among not only a greater number, but a number inex- 

 1 austible by us, and to which as we know no bounds, they may, so far as 

 ■< ^e are concerned, be regarded as infinite. 



There is no impropriety in saying that, of these two classifications^ the 

 ( ne answers to a much more radical distinction in the things themselves, 

 t lan the other does. And if any one even chooses to say that the one clas- 



1 



