122 THE PRINCIPLES OF SCIENCE. [chap. 



combinations agreeing with those conditions. Our work 

 has been to unfold the results of what is contained in any 

 statements, and the process has been one of Synthesis. 

 The terms or combinations of which the character has 

 been determined have usually, though by no means always, 

 involved more qualities, and therefore, by the relation of 

 extension and intension, fewer objects than the terms in 

 which they were described. The truths inferred were thus 

 usually less general than the truths from which they were 

 inferred. 



In induction all is inverted. The truths to be ascer- 

 tained are more general than the data from which they 

 are drawn. The process by which they are reached is 

 analytical, and consists in separating the complex com- 

 binations in which natural plienomena are presented to 

 us, and determining the relations of separate qualities. 

 Given events obeying certain unknown laws, we have to 

 discover the laws obeyed. Instead of the comparatively 

 easy task of finding what effects will follow from a given 

 law, the effects are now given and the law is required. 

 We have to interpret the will by which the conditions 

 of creation w*ere laid down. 



Induction an Inverse Oiperation 



I have already asserted that induction is the inverse 

 operation of deduction, but the difference is one of such 

 great importance that I must dwell upon it. There are 

 many cases in which we can easily and infallibly do a 

 certain thing but may have much trouble in undoing it. 

 A person may walk into the most complicated labyrinth 

 or the most extensive catacombs, and turn hither and thither 

 at his will ; it is when he wishes to return that doubt and 

 difficulty commence. In entering, any path served him ; 

 in leaving, he must select certain definite paths, and in this 

 selection he must either trust to memory of the way he 

 entered or else make an exhaustive trial of all possible 

 ways. The explorer entering a new country makes sure 

 liis line of return by barking the trees. 



The same difficulty arises in many scientific processes. 

 Given any two numbers, we may by a simple and infallible 

 l)rocess obtain their product ; but when a large number 



