36 MAC Leod, The Place of Science in History. 



here it is more easy to correct the mistakes committed. 

 It is indeed ordinarily possible to survey a large number 

 of facts, and is in consequence much easier to discover 

 exceptions and to ascertain that an imagined discovery 

 of a law is only that of a rule. Moreover the active 

 intervention of the experimenter makes it possible to verify 

 whether a so-called law deserves that name. 



The study of natural science and its applications 

 teaches us that knowledge of the laws of nature enables 

 man to subdue and overcome nature. 



When the naturalist or the doctor has discovered a 

 rule, the effects of which are harmful, he does not content 

 himself with recording the fact with resignation. He 

 endeavours to combat these effects, and very often he 

 succeeds. 



One may say, for example, that it is a natural law that 

 cultivated fields should be overrun with weeds. If one 

 contents oneself with the simple observation of the facts, 

 this would seem to be a real law, because it is certainly 

 impossible to discover a cultivated field without weeds. 

 But the active intervention of the experimenter teaches 

 us that it is only a simple rule which is here in question. 

 It is indeed possible to pull up the weeds and thus 

 diminish their ravages. And if one perseveres for some 

 years, working methodically, and preventing the harmful 

 weeds from bearing ripe seeds, one can succeed in sup- 

 pressing them altogether. This has been done, and the 

 advantages obtained are notably greater than the expense 

 incurred. 



But even when one is dealing with the effects of a 

 real law, one can often combat it with success. One of 

 the best examples one could take is the following : it is a 

 natural law that bodies fall in consequence of the force of 

 gravity. But it is possible to construct balloons which 



