ABSTRACTION. 463 



thing which distinguishes them from all othei' things, but agree with each 

 other and differ from other things in the very circumstances which are of 

 primary importance for the purpose (theoretical or practical) which we 

 have in view, and which constitutes the problem before us. In other 

 words, our conceptions, though they may be clear, are not appropriate for 

 our purpose, unless the properties we comprise in them are those which 

 will help us toward what we wish to understand — ^. e., either those which go 

 deepest into the nature of the things, if our object be to understand that, 

 or those which are most closely connected with the particular property 

 which we are endeavoring to investigate. 



We can not, therefore, frame good general conceptions beforehand. 

 That the conception we have obtained is the one we want, can only be 

 known when we have done the work for the sake of which we wanted it ; 

 when we completely understand the general character of the phenomena, 

 or the conditions of the particular property with which we concern our- 

 selves. General conceptions formed without this thorough knowledge, are 

 Bacon's "notiones temere a rebus abstractae." Yet such premature con- 

 ceptions we must be continually making up, in our progress to something 

 better. They are an impediment to the progress of knowledge, only when 

 they are permanently acquiesced in. When it has become our habit to 

 group things in wrong classes — in groups which either are not really class- 

 es, having no distinctive points of agreement (absence of clear ideas), or 

 which are not classes of which any thing 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 ex- 

 change them for others, and can not 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 abstractae " 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 ex- 

 pression to say, that obtaining appropriate conceptions is a condition pre- 

 cedent 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 phenom- 

 ena. As we obtain more knowledge of the phenomena themselves, and of 

 the conditions on which their important properties depend, our views on 

 this subject naturally alter; and thus we advance from a less to a more 

 "appropriate" general conception, in the progress of our investigations. 



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

 agreement can not 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 our- 

 selves in a sufficiently commanding position, and cast our eyes round us, 

 and if we can see the object it is well ; if not, m'c 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 it illustrates, we first endeavor to find the lost object or 



