METHOD OF DISCOVERY. 57 



kind of difference, between the mental operations of a 

 man of science and those of an ordinary person, as 

 there is between the operations and methods of a baker 

 or of a butcher weighing out his goods in common 

 scales, and the operations of a chemist in performing 

 a difficult and complex analysis by means of his balance 

 and finely-graduated weights. It is not that the action 

 of the scales in the one case, and the balance in the 

 other, differ in the principles of their construction or 

 manner of working; but the beam of one is set on an 

 infinitely finer axis than the other, and of course turns 

 by the addition of a much smaller weight. 



You will understand this better, perhaps, if I give 

 you some familiar example. You have all heard it re- 

 peated, I dare say, that men of science work by means 

 of Induction and Deduction, and that by the help of 

 these operations, they, in a sort of sense, wring from 

 Nature certain other things, which are called Natural 

 Laws, and Causes, and that out of these, by some 

 cunning skill of their own, they build up Hypotheses 

 and Theories. And it is imagined by many, that the 

 operations of the common mind can be by no means 

 compared with these processes, and that they have to be 

 acquired by a sort of special apprenticeship to the 

 craft. To hear all these large words, you would think 

 that the mind of a man of science must be constituted 

 differently from that of his fellow men ; but if you will 

 not be frightened by terms, you will discover that you 

 are quite wrong, and that all these terrible apparatus 

 are being used by yourselves every day and every hour 

 of your lives. 



