104 NAMES AND PROPOSITIONS. 



name. The name given to them in common, is what makes 

 them a class. To refer anything to a class, therefore, is to 

 look upon it as one of the things which are to be called by 

 that common name. To exclude it from a class, is to say that 

 the common name is not applicable to it. 



How widely these views of predication have prevailed, is 

 evident from this, that they are the basis of the celebrated 

 dictum de omni et nullo. When the syllogism is resolved, by 

 all who treat of it, into an inference that what is true of a 

 class is true of all things whatever that belong to the class ; 

 and when this is laid down by almost all professed logicians 

 as the ultimate principle to which all reasoning owes its 

 validity ; it is clear that in the general estimation of logi- 

 cians, the propositions of which reasonings are composed 

 can be the expression of nothing but the process of dividing 

 things into classes, and referring everything to its proper 

 class. 



This theory appears to me a signal example of a logical 

 error very often committed in logic, that of vorc/oov trpoTtpov, 

 or explaining a thing by something which presupposes it. 

 When I say that snow is white, I may and ought to be think- 

 ing of snow as a class, because I am asserting a proposition 

 as true of all snow : but I am certainly not thinking of white 

 objects as a class; I am thinking of no white object whatever 

 except snow, but only of that, and of the sensation of white 

 which it gives me. When, indeed, I have judged, or assented 

 to the propositions, that snow is white, and that several other 

 things are also white, I gradually begin to think of white 

 objects as a class, including snow and those other things. But 

 this is a conception which followed, not preceded, those judg- 

 ments, and therefore cannot be given as an explanation of 

 them. Instead of explaining the effect by the cause, this 

 doctrine explains the cause by the effect, and is, I conceive, 

 founded on a latent misconception of the nature of classifi- 

 cation. 



There is a sort of language very generally prevalent in 

 these discussions, which seems to suppose that classification 

 is an arrangement and grouping of definite and known indi- 



