8 DEGENERATION I I 



series of events constituting the universe, to any and 

 every thing which we can perceive. 



The method by which scientific knowledge is 

 gained — knowledge of the causes of nature — is pre- 

 cisely the same as that by which knowledge of causes 

 in everyday life is gained. Something — an appear- 

 ance — has to be accounted for : the question in both 

 cases is, " Through what cause, in relation to what 

 antecedent is this appearance brought about?" In 

 scientific inquiry, as in everyday life, a hypothesis — 

 a provisional answer or guess — is the reply ; and the 

 truth of that guess or hypothesis is then tested. This 

 testing is an essential part of the process. " If my 

 guess be true, then so-and-so as to which I can decide 

 by inspection or experiment, must be true also," is 

 the form which the argument takes, and the inquiry is 

 thus brought to a point where observation can decide 

 the truth of the hypothesis or first guess. In every- 

 day life we have often to be content without fully 

 testing the truth of our guesses, and hurry into action 

 based on such unverified suppositions. Science, on 

 the other hand, can always wait, and demands again 

 and again the testing and verification of guesses 

 before they are admitted as established truths fit to 

 be used in the testing of new guesses and the building 

 up of scientific doctrine. 



The delicately -reared imaginations of great investi- 

 gators of natural things have from time to time given 

 birth to hypotheses — guesses at truth — which have 

 suddenly transformed a whole department of know- 

 ledge, and made the causes of things quite clear 



