CLASSIFICATION. 



47^ 



it is in contemplation not f>f those 

 characters only which are rigorotisly 

 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 concep- 

 tion of the class, the image in our 

 minds which is representative of it, 

 is that of a specimen complete in 

 all the characters ; most naturally a 

 specimen which, by possessing them 

 all in the greatest degree in which 

 they are ever found, is the best fitted 

 to exhibit clearly, and in a marked 

 manner, what they are. It is by a 

 mental reference to this standard, 

 not instead of, but in illustration of, 

 the definition of the class, that we 

 usually and advantageously determine 

 whether any individual or species 

 belongs to the class or not. And 

 this, as it seems to me, is the amount 

 of truth contained in the doctrine of 

 Types. 



We shall see presently that where 

 the classification is made for the ex- 

 press purpose of a sj^ecial inductive 

 inc^uiry, it is not optional, but neces- 

 sary 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 par- 

 ticular phenomenon under investiga- 

 tion. But of this hereafter. It re- 

 niains, for completing the theory of 

 natural groups, that a few words 

 should be said on the principles of 

 the nomenclature adapted to them. 



§ 5. A Nomenclature in science is, 

 as we have said, a system of the 

 names of Kinds. These names, like 

 other class-names, are defined by the 

 enumeration of the characters distinc- 

 tive 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 informa- 

 tion as possible, so that a person who 

 knows the thing may receive all the 

 assistance which the name can give 

 in remembering what he knows, while 



he who knowa 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 signi- 

 ficance. The best, but which unfor- 

 tunately 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 not, of course, 

 connote all the properties of the Kind, 

 since these are inexhaustible, but such 

 of them as are sufficient to distinguish 

 it ; such as are sure marks of all the 

 rest. Now, it is very rarely that one 

 property, or even any two or three 

 properties, can answer this purpose. 

 To distinguish the common daisy from 

 all other species of plants would re- 

 quire the specification of many char- 

 acters. And a name cannot, without 

 being too cumbrous for use, give 

 indication, by its etymology or mode 

 of construction of more than a very 

 small number of these. The possi- 

 bility, therefore, of an ideally perfect 

 Nomenclature is probably confined to 

 the one case in which we are happily 

 in possession of something approach- 

 ing to it — the Nomenclature of Ele- 

 mentary Chemistry. The substances, 

 whether simple or compound, with 

 which chemistry is conversant, are 

 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) 

 there is one property, the chemical 

 composition, which is of itself suffi- 

 cient to distinguish the Kind, and 

 is (with certain reservations not yet 

 thoroughly understood) a sure mark 

 of all the other proj?erties of the com- 

 pound. All that was needful, there- 

 fore, was to make the name of every 

 compound express on the first hearing 

 its chemical composition ; that is, to 

 form the name of the compound in 

 some uniform manner from the names 

 of the simple substances which enter 



