122 INDUCTION. 



explained in some detail what is meant by the Kinds 

 of objects*, those classes which differ from one 

 another not by a limited and definite, but by an 

 indefinite and unknown, number of distinctions. To 

 this we have now to add, that every proposition by 

 which anything is asserted of a Kind, affirms an uni- 

 formity of coexistence. Since we know nothing of 

 Kinds but their properties, the Kind, to us, is the set of 

 properties by which it is identified, and which must of 

 course be sufficient to distinguish it from every other 

 Kindf. In affirming anything, therefore, of a Kind, 

 we are affirming something to be uniformly coexistent 

 with the properties by which the Kind is recognised ; 

 and that is the sole meaning of the assertion. 



Among the uniformities of coexistence which 

 exist in nature, may hence be numbered all the pro- 

 perties of Kinds. The whole of these, however, are 

 not independent of causation, but only a portion of 

 them. Some are ultimate properties, others deriva- 

 tive; of some, no cause can be assigned, but others 

 are manifestly dependent upon causes. Thus, atmo- 

 spheric air is a Kind, and one of its most unequi- 

 vocal properties is its gaseous form: this property, 



* Supra, book i., chap. vii. 



t In some cases, a Kind is sufficiently identified by some one 

 remarkable property; but most commonly several are required; 

 each property, considered singly, being a joint property of that and 

 of other Kinds. The mere colour and brightness of the diamond are 

 common to it with the paste from which false diamonds are made ; 

 the double refraction is common to it with Iceland spar, and many 

 other stones ; but the colour and brightness and the double refrac- 

 tion together, identify its Kind ; that is, are a mark to us that it is 

 combustible; that when burnt it produces carbonic acid; that it 

 cannot be cut with any known substance; together with many other 

 ascertained properties, and the fact that there exist an indefinite 

 number still unascertained. 



