PREFACE 



EVERY scientific book has three sorts of readers : 

 experts draw upon it for information and facts, 

 doctrinaires find arguments and laymen seek 

 ideas in it. This book is not written for the 

 first; it makes no pretension of presenting a 

 summary of the results obtained by the sciences, 

 and facts are cited only in so far as they tend to 

 define the meanings and explain the origin of 

 scientific ideas. Nor have I tried to settle the 

 eternal dispute of religious and philosophical 

 doctrines, to judge cosmogonies, or to throw 

 light upon the origin and destiny of man and 

 the universe. Experience proves that in this 

 matter each one listens only to the arguments 

 favourable to his standpoint and reads only the 

 books on his own side. Happily doctrinaires 

 are people easy to satisfy, provided one does 

 not contradict them directly; they will find in 

 these pages arguments favourable to their ideas 

 and will not see those which contradict them. 



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