146 GENERAL VIEW AND BASIS OF SCIENTIFIC RESEARCH. 



health. The truthfulness of our ideas also depends upon 

 the accuracy and completeness with which we reason upon 

 our impressions, and draw conclusions from them. The 

 less intelligent or truthful our minds, the greater is the 

 proportion of impressions we receive in a false or distorted 

 manner, and of false inferences we draw from them. As 

 far as we know,, the experience of all mankind, through all 

 ages, confirms the conclusion, that all the operations of 

 nature are absolutely certain. Uncertainty, therefore, exists 

 not in the phenomena of nature, but in our mental recep- 

 tion and exposition of them. As nature itself is true, and 

 we are very liable to transform truth into error in the act 

 of receiving and interpreting it, our thoughts are not a test 

 of the truthfulness of nature, but nature is the test of the 

 truth of our thoughts, and our minds must be brought to 

 agree with it. 1 



Another reason why our scientific knowledge is not in- 

 fallible is because our inductions are never complete. We 

 never make an exhaustive enumeration of all the instances, 

 because it is either beyond our power, or the labour is too 

 great. We also never know that undiscovered instances 

 do not remain, or that we have not omitted some excep- 

 tional cases. Induction, therefore, never absolutely proves 

 a general law, nor can we ever be absolutely certain that 

 the next discovered instance will not be an exceptional one. 



The strongest proof of the truth of a general law is 

 usually considered to be the successful prediction of new 

 results ; but even in this case we are not absolutely cer- 

 tain, because our deductions also are never complete. 

 Until we have predicted, and successfully verified every 

 possible case, and that is beyond our powers, we are not 

 certain we have not missed some exceptional one, and that 

 our prediction may not be wrong. The extreme incom- 



1 For limiting exceptions see p. 23. 



