ABSTRACTION. 227 



The principal requisites, therefore, of clear con- 

 ceptions, are habits of attentive observation, an exten- 

 sive experience, and a memory which receives and 

 retains an exact image of what is observed. And in 

 proportion as any one has the habit of observing 

 minutely and comparing carefully a particular class 

 of phenomena, and an accurate memory for the results 

 of the observation and comparison, so will his con- 

 ceptions of that class of phenomena be clear ; provided 

 he has the indispensable habit, (naturally, however, 

 resulting from those other endowments,) of never using 

 general names without a precise connotation. 



As the clearness of our conceptions chiefly de- 

 pends upon the carefulness and accuracy of our 

 observing and comparing faculties, so their appropri- 

 ateness, or rather the chance we have of hitting upon 

 the appropriate conception in any case, mainly depends 

 upon the activity of the same faculties. He who by 

 habit, grounded on sufficient natural aptitude, has 

 acquired a readiness in accurately observing and com- 

 paring phenomena, will perceive so many more agree- 

 ments and will perceive them so much more rapidly 

 than other people, that the chances are much greater 

 of his perceiving, in any instance, the agreement on 

 which the important consequences depend. 



6. We are not, at the same time, to forget, that 

 the agreement cannot always be discovered by mere 

 comparison of the very phenomena in question, with- 

 out 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 pheno- 

 mena is in truth very similar to the search for a lost 

 or hidden object. At first we place ourselves in a 

 sufficiently commanding position, and cast our eyes 



Q 2 



