34:6 PERSONAL PREPARATION FOR RESEARCH. 



any degree of similarity, and in proportion as their degree 

 of likeness diminishes^ so does the difficulty of drawing 

 conclusions from them usually increase. The great prac- 

 tical difficulty, in nearly all cases, lies not so much in 

 drawing the conclusions (though that is often a difficult 

 matter) as in determining what really are identities, 

 similarities, or differences, and to what extent identity, 

 similarity, or difference actually exists. The difficulty of 

 drawing correct conclusions usually increases also in pro- 

 portion to the increase of complexity of the phenomena, 

 because the human mind can only contemplate a few 

 things at a time. 



All our knowledge of science is primarily derived from 

 facts and experience, and as our senses are not capable 

 of immediately perceiving general truths, all our know- 

 ledge of laws and principles, and all the further informa- 

 tion derived from that knowledge by reasoning processes, 

 is inductive in its origin. 



In experimental research it is found that the action of 

 induction and deduction is reciprocal and often alternate, 

 and that sometimes one precedes and sometimes the other. 

 For instance, we observe facts, and inductively infer a law 

 which expresses them ; we deduce new facts from that 

 law, and then prove their existence by experiment ; from 

 the larger collection of facts thus obtained we next induc- 

 tively infer a more general law, and then deduce new con- 

 sequences in a similar way ; from a collection of less 

 general laws thus obtained we next inductively infer a 

 more general law, and then deduce new consequences in a 

 similar way ; from a collection of less general laws thus 

 obtained we sometimes also ascend by induction to a 

 greater one, and so on until the limits of our powers are 

 reached. Sometimes we ascend by induction to a general 

 principle, and then descend by deduction to particular 



