COSMIC PHILOSOPHY 



have some weight with a jury of inquirers fa- 

 miliar with the history of human thinking. On 

 the other hand a theory is a priori accredited by 

 its pedigree when it is framed in a cultivated age 

 by thinkers familiar alike with the special phe- 

 nomena which form its subject matter and with 

 the requirements of scientific hypothesis in gen- 

 eral ; and when, in spite*of theological or senti- 

 mental prejudice, it so thrives under the most 

 rigorous critical scrutiny that each successive 

 decade enlists in its support a greater and greater 

 number of the most competent investigators of 

 nature. I do not say that such an a priori pre- 

 sumption should ever be taken as decisive in 

 favour of any hypothesis. I say only that such 

 considerations do have their weight, and ought 

 to have their weight, in determining the general 

 state of mind which we bring to the discussion 

 of the relative merits of two theories so different 

 in their pedigrees as are the two theories which 

 we are now about to examine. If, with my eyes 

 closed upon all the significant facts which bear 

 upon the question of the origin of species, I 

 were required to decide between two hypotheses, 

 of which the one was framed in an. age when 

 the sky was supposed to be the solid floor of a 

 celestial ocean, while the other was framed in an 

 age when Lagrange and Laplace were determin- 

 ing the conditions of equilibrium of the solar 

 system, I should at once decide, on general 

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