CLASSIFICATION. 441 



classes, iletennincd by ('haract(!i\s ; tlioy arc constituted in ccMiteinpla- 

 tion of, and by reason of, characters. But it is in contemplation not of 

 those characters only which are rigorously common to all the objects 

 included in the group, but of the entire body of characters, all of which 

 are found in most of those objects, and most of them in all. And 

 hence our conception of the class, the image in our minds which is 

 representative of it, is that of a specimen complete in all the charac- 

 ters ; most naturally a sjiecimen which, by possessing them all in the 

 greatest degiee in which they are ever found, is the best fitted to ex- 

 hibit clearly, and in a inarked maimer, what they arc. It is by a mental 

 referLMice to this standard, not instead of, but in illustration of, the 

 delinirion of the class, that we usually and advantageously determine 

 wliether any individual or species belongs to the class or not. And 

 this, as it seems to me, is the amount of truth which is containe'd in 

 Mr. Whewell's doctrine of Types. 



We shall see presently that where the classification is made for the 

 express purpose oi a special inductive inquiry, it is not o[)tional, but 

 necessary for fulfilling the conditions of a correct Inductive Method, 

 that we should establish a type-species or genus, namely, the one which 

 exhibits in the most eminent degree the particular phenomenon under 

 investigation. But of this hereafter. It remains, for completing the 

 theory of natural groups, that a few words should be said on the 

 principles of the nomenclature adapted ta them. 



§ 5. A Nomenclature, as we have said, is a system of the names of 

 Kinds. These names, like other class-names, are defined by the 

 enumeration of the characters distinctive of the class. The only merit 

 which a set of names can have beyond this, is to convey, by the mode 

 of their construction, as much information as possible : so that a per- 

 son who knows the thing, may receive all the assistance which the 

 name can give in remembering what he knows, while he who knows 

 it not, may receive as much knowledge respecting it as the case admits 

 of, by merely being told its name. 



There are two modes of giving to the name of a kind this sort of 

 significance. The best, but which unfortunately is seldom practicable, 

 is when the word can be made to indicate, by its formation, the very 

 properties which it is designed to connote. The name of a kind does 

 hot, of course, connote all the properties of the kind, since these are 

 inexhaustible, bilt such of tliem as are sufficient to distinguish it; such 

 as are sure marks of all the rest. Now, it is very rare that one 

 property, or even any two or three properties, can answer this pur- 

 pose. To distinguish the common daisy from all other species ot 

 plants would require the specification of many characters. And a 

 name cannot, without being too cumbrous for use, give indication, by 

 its etymology or mode of constructicm, of more than a very small 

 number of these. The possibility, therefore, of an ideally perfect 

 Nomenclature, is probably confined to the one case in which we are 

 happily in possession of something lujiirly approacliing to it; 1 refer to 

 the Nomenclature of Chemistry. Tlu; substances, whether simple or 

 compound, with which chemistry is conversant, arc Kinds, and, as 

 such, the properties which distinguish each of them from the rest, are 

 innumerable ; but in the case of compound substances (the simple 

 ones are not numerous enough to require a systematic nomenclature), 

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