18 INDUCTION. 



his own rule. And Mr. Whewell is clearly right in 

 denying it to be necessary that the cause assigned 

 should be a cause already known ; else how could we 

 ever become acquainted with any new cause ? But what 

 is true in the maxim is, that the cause, although not 

 known previously, should be capable of being known 

 thereafter; that its existence should be capable of 

 being detected, and its connexion with the effect 

 ascribed to it, susceptible of being proved, by inde- 

 pendent evidence. The hypothesis, by suggesting 

 observations and experiments, puts us upon the road 

 to that independent evidence if it be really attainable; 

 and till it be attained, the hypothesis ought not to 

 count for more than a suspicion. 



5. This function, however, of hypotheses, is one 

 which must be reckoned absolutely indispensable in 

 science. When Newton said, " Hypotheses non 

 fingo," he did not mean that he deprived himself of 

 the facilities of investigation afforded by assuming in 

 the first instance what he hoped ultimately to be able 

 to prove. Without such assumptions, science could 

 never have attained its present state : they are neces- 

 sary steps in the progress to something more certain; 

 and nearly everything which is now theory was once 

 hypothesis. Even in purely experimental science, 

 some inducement is necessary for trying one expe- 

 riment rather than another; and although it is 

 abstractedly possible that all the experiments which 

 have been tried, might have been produced by the 

 mere desire to ascertain what would happen in 

 certain circumstances, without any previous conjec- 

 ture as to the result ; yet in point of fact those 

 unobvious, delicate, and often cumbrous and tedious 

 processes of experiment, which have thrown most 



