METHOD OF DISCOVERY 49 



Deduction, and reasoned out the special conclusion of the 

 particular case. Well now, suppose, having got your law, 

 that at some time afterwards, you are discussing the 

 qualities of apples with a friend : you will say to him, 

 " It is a very curious thing, but I find that all hard and 

 green apples are sour ! " Your friend says to you, " But 

 how do you know that ? " You at once reply, " Oh, 

 because I have tried it over and over again, and have 

 always found them to be so." Well, if we were talking 

 science instead of common sense, we should call that an 

 Experimental Verification. And, if still opposed, you 

 go further, and say, " I have heard from the people in 

 Somersetshire and Devonshire, where a large number of 

 apples are grown, that they have observed the same thing. 

 It is also found to be the case in Normandy, and in North 

 America. In short, I find it to be the universal experience 

 of mankind wherever attention has been directed to the 

 subject." Whereupon, your friend, unless he is a very 

 unreasonable man, agrees with you, and is convinced that 

 you are quite right in the conclusion you have drawn. 

 He believes, although perhaps he does not know he believes 

 it, that the more extensive Verifications are, that the 

 more frequently experiments have been made, and results 

 of the same kind arrived at, that the more varied the 

 conditions under which the same results have been attained, 

 the more certain is the ultimate conclusion, and he disputes 

 the question no further. He sees that the experiment 

 has been tried under all sorts of conditions, as to time, 

 place, and people, with the same result ; and he says with 

 you, therefore, that the law you have laid down must 

 be a good one, and he must believe it. 



In science we do the same thing ; the philosopher 

 exercises precisely the same faculties, though in a much 

 more delicate manner. In scientific inquiry it becomes 

 a matter of duty to expose a supposed law to every possible 

 kind of verification, and to take care, moreover, that 

 this is done intentionally, and not left to a mere accident, 

 as in the case of the apples. And in science, as in common 

 life, our confidence in a law is in exact proportion to the 

 absence of variation in the result of our experimental veri- 

 fications. For instance, if you let go your grasp of an 

 article you may have in your hand, it will immediately 

 fall to the ground. That is a very common verification 

 of one of the best established laws of nature that of 



