METHOD OF DISCOVERY. 65 



mode of reasoning was employed by Newton and 

 Laplace in their endeavours to discover and define the 

 causes of the movements of the heavenly bodies, as you, 

 with your own common sense, would employ to detect 

 a burglar. The only difference is, that the nature of 

 the inquiry being more abstruse, every step has to be 

 most carefully watched, so that there may not be a 

 single crack or flaw in your hypothesis. A flaw or 

 crack in many of the hypotheses of daily life may be 

 of little or no moment as affecting the general correct- 

 ness of the conclusions at which we may arrive ; but 

 in a scientific inquiry a fallacy, great or small, is alwa} 7 s 

 of importance, and is sure to be constantly productive 

 of mischievous, if not fatal, results in the long run. 



Do not allow yourselves to be misled by the com- 

 mon notion that a hypothesis is untrustworthy simply 

 because it is a hypothesis. It is often urged, in respect 

 to some scientific conclusion, that, after all, it is only 

 a hypothesis. But what more have we to guide us in 

 nine-tenths of the most important affairs of daily life 

 than hypotheses, and often very ill-based ones? So 

 that in science, where the evidence of a hypothesis is 

 subjected to the most rigid examination, we may rightly 

 pursue the same course. You may have hypotheses 

 and hypotheses. A man may say, if he likes, that the 

 moon is made of green cheese : that is a hypothesis. 

 But another man, who has devoted a great deal of time 

 and attention to the subject, and availed himself of the 

 most powerful telescopes and the results of the observa- 

 tions of others, declares that in his opinion it is prob- 

 ably composed of materials very similar to those of 

 which our own earth is made up : and that is also only a 

 hypothesis. But I need not tell you that there is an 



