REFLECTIONS AND CONCLUSION. 399 



others, history but repeats itself and demonstrates 

 again, that opposition may be a source of strength, 

 and contradiction the most effective means of secur- 

 ing certitude and light. For we must bear in mind 

 that it is not mistaken theory that retards the prog- 

 ress of science, but rather erroneous observations. 

 All working scientists are aware, often to their cost, 

 that it is inaccurate or mistaken observations which 

 lead men astray, while erroneous theories have often 

 a most stimulating effect. They suggest and pro- 

 voke new and more exact observations, and thus lead 

 up to true theories and ultimately to a true knowl- 

 edge of nature. 



Errors in the Infancy of Science. 



It is indeed a difficult matter for those who live 

 in the closing years of the nineteenth century, duly 

 to appreciate the mental attitude of those who lived 

 and taught a thousand or two thousand years ago. 

 It is difficult even for us to account for the extrava- 

 gant views held by distinguished scientists of com- 

 paratively recent times, by such men, for example, 

 as Kepler, Stahl, Kircher, Buckland and others of 

 their contemporaries. We smile at the fantastic no- 

 tions which they entertained respecting some of the 

 most ordinary phenomena of astronomy, chemistry, 

 biology and geology. But we forget that we are liv- 

 ing in the full effulgence of inductive science, and 

 that we have the benefit of the labors of thousands 

 and tens of thousands of investigators in every de- 

 partment of thought. We forget that Kepler and 



