ABSTRACTION. 207 



ideas), or which are not classes of which anything important 

 to our purpose can be predicated (absence of appropriate 

 ideas) ; and when, in the belief that these badly made classes 

 are those sanctioned by Nature, we refuse to exchange them 

 for others, and cannot or will not make up our general con- 

 ceptions from any other elements ; in that case all the evils 

 which Bacon ascribes to his "notiones temere abstract " 

 really occur. This was what the ancients did in physics, and 

 what the world in general does in morals and politics to the 

 present day. 



It would thus, in my view of the matter, be an inaccurate 

 mode of expression to say, that obtaining appropriate concep- 

 tions is a condition precedent to generalization. Throughout 

 the whole process of comparing phenomena with one another 

 for the purpose of generalization, the mind is trying to make 

 up a conception ; but the conception which it is trying to 

 make up is that of the really important point of agreement in 

 the phenomena. As we obtain more knowledge of the pheno- 

 mena themselves, and of the conditions on which their impor- 

 tant properties depend, our views on this subject naturally 

 alter ; and thus we advance from a less to a more " appro- 

 priate" general conception, in the progress of our investi- 

 gations. 



We ought not, at the same time, to forget that the really 

 important agreement cannot always be discovered by mere 

 comparison of the very phenomena in question, without the 

 aid of a conception acquired elsewhere ; as in the case, so often 

 referred to, of the planetary orbits. 



The search for the agreement of a set of phenomena is in 

 truth very similar to the search for a lost or hidden object. 

 At first we place ourselves in a sufficiently commanding posi- 

 tion, and cast our eyes round us, and if we can see the object 

 it is well ; if not, we ask ourselves mentally what are the 

 places in which it may be hid, in order that we may there 

 search for it : and so on, until we imagine the place where it 

 really is. And here too we require to have had a previous 

 conception, or knowledge, of those different places. As in 

 this familiar process, so in the philosophical operation which 



