The Duty of Doubt 233 



learn to distinguish in our minds those matters which 

 we know directly from those matters which we have 

 accepted on trust ; and, secondly, to learn and to apply 

 the best modes of choosing the good and of rejecting 

 the bad authorities. The work of the scientific man is a 

 lifelong exercise of these primary duties. From the 

 first moment he begins to observe living things or to 

 dissect their dead frameworks, to mix chemical sub- 

 stances, to make experiments with magnets and wires, 

 he begins to build, and as long as he continues to 

 work he continues to build for himself a body of first- 

 hand knowledge. But, however he work arduously or 

 through long years, he can visit only the smallest por- 

 tion of the field of nature in which he is working. It 

 is necessary for him to employ the work of others, sub- 

 mitting, from time to time such accepted work to the 

 tests suggested by his own observations. He learns to 

 regard in a different light all knowledge taken on the 

 authority of others ; to distrust it a little until he has 

 learned to weigh its general credibility by his own 

 standards, and its particular credibility by subject- 

 ing portions of it to his own tests ; to distrust it still 

 more when even small portions fail to answer his tests, 

 and to reject it altogether when the percentage of de- 

 tected error is large. He learns, in fact, what Huxley 

 called the duty of doubt. 



This duty has not been universally accepted. In the 

 histor}^ of Christian civilisation (and a parallel series 

 of events might be portraj^ed from the history of other 

 civilisations), many great institutions and very many 

 great and good men have condemned and feared the 

 habit and attitude of doubt in all its forms. Certain 

 doctrines believed to be of supreme importance to man- 

 kind were held to rest on authority independent of, 



