SCIENTIFIC INVESTIGATION 93 



sense in leading him to a conclusion as to the course he 

 should take in order to make good a robbery and punish 

 the offender. I say that you are led, in that case, to your 

 conclusion by exactly the same train of reasoning as 

 that which a man of science pursues when he is en- 

 deavouring to discover the origin and laws of the most 

 occult phenomena. The process is, and always must 

 be, the same ; and precisely the same mode of reasoning 

 was employed by Newton and Laplace in their en- 

 deavours to discover and define the causes of the move- 

 ments 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 correctness of the conclusions 

 at which we may arrive; but, in a scientific inquiry, a 

 fallacy, great or small, is always of importance, and is 

 sure to be in the long run constantly productive of 

 mischievous if not fatal results. 



Do not allow yourselves to be misled by the common 

 notion that an hypothesis is untrustworthy simply be- 

 cause it is an hypothesis. It is often urged, in respect 

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

 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 an hypothesis is sub- 

 jected to the most rigid examination, we may rightlj 

 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 an hypothesis. 



