118 INDUCTION. 



even the same infima species, or lowest Kind. Some flowers may 

 be either white or red, without differing in any other respect. 

 But these properties are not ultimate ; they depend on causes. 

 So far as the properties of a thing belong to its own nature, 

 and do not arise from some cause extrinsic to it, they are 

 always the same in the same Kind. Take, for instance, all 

 simple substances and elementary powers ; the only things 

 of which we are certain that some at least of their properties 

 are really ultimate. Colour is generally esteemed the most 

 variable of all properties : yet we do not find that sulphur is 

 sometimes yellow and sometimes white, or that it varies in 

 colour at all, except so far as colour is the effect of some 

 extrinsic cause, as of the sort of light thrown upon it, the 

 mechanical arrangement of the particles, (as after fusion) &c. 

 We do not find that iron is sometimes fluid and sometimes 

 solid at the same temperature ; gold sometimes malleable and 

 sometimes brittle ; that hydrogen will sometimes combine 

 with oxygen and sometimes not ; or the like. If from simple 

 substances we pass to any of their definite compounds, as 

 water, lime, or sulphuric acid, there is the same constancy in 

 their properties. When properties vary from individual to 

 individual, it is either in the case of miscellaneous aggrega 

 tions, such as atmospheric air or rock, composed of hetero 

 geneous substances, and not constituting or belonging to 

 any real Kind,* or it is in the case of organic beings. In 

 them, indeed, there is variability in a high degree. Animals 

 of the same species and race, human beings of the same 

 age, sex, and country, will be most different, for example, in 

 face and figure. But organized beings (from the extreme 

 complication of the laws by which they are regulated) being 

 more eminently modifiable, that is, liable to be influenced by 

 a greater number and variety of causes, than any other 

 phenomena whatever; having also themselves had a begin 

 ning, and therefore a cause ; there is reason to believe that 



* This doctrine of course assumes that the allotropic forms of what is 

 chemically the same substance are so many different Kinds ; and such, in the 

 sense in which the word Kind is used in this treatise, they really are. 



