PART IV. NATURE 

 Hypotheses in Physics 



The Role of Experiment and Generalization. Experiment is the 

 sole source of truth. It alone can teach us something new; it alone 

 can give us certainty. These are two points that cannot be ques- 

 tioned. But then, if experiment is everything, what place is left for 

 mathematical physics? What can experimental physics do with such 

 an auxiliary an auxiliary, moreover, which seems useless, and even 

 may be dangerous? 



However, mathematical physics exists. It has rendered undeniable 

 service, and that is a fact which has to be explained. It is not suffi- 

 cient merely to observe; we must use our observations, and for that 

 purpose we must generalize. This is what has always been done, only 

 as the recollection of past errors has made man more and more circum- 

 spect, he has observed more and more and generalized less and less. 

 Every age has scoffed at its predecessor, accusing it of having gener- 

 alizet too boldly and too naively. Descartes used to commiserate the 

 lonians. Descartes in his turn makes us smile, and no doubt some 

 day our children will laugh at us. Is there no way of getting at once 

 to the gist of the matter, and thereby escaping the raillery which we 

 foresee? Cannot we be content with experiment alone? No, that is 

 impossible; that would be a complete misunderstanding of the true 

 character of science. The man of science must work with method. 

 Science is built up of facts, as a house is built of stones ; but an accu- 

 mulation of facts is no more a science than a heap of stones is a 

 house. Most important of all, the man of science must exhibit fore- 

 sight. Carlyle has written somewhere something after this fashion. 

 " Nothing but facts are of importance. John Lackland passed by 

 here. Here is something that is admirable. Here is a reality for 

 which I would give all the theories in the world." 1 Carlyle was a 

 compatriot of Bacon, and, like him, he wished to proclaim his worship 

 of the God of Things as they are. 



But Bacon would not have said that. That is the language of the 

 historian. The physicist would most likely have said : " John Lack- 



i V. Past and Present, end of Chapter I., Book II. [TR.] 



