PREFACE xi 



we are led finally to a much smaller number of names than 

 are usually mentioned in historical works, even those of the 

 smaller kind, for it appears that the writers of such books 

 are more anxious to name the maximum number of persons, 

 than to be at the trouble of forming a judgment by going 

 back to the sources. But since in the present work the object 

 was to deal with the great investigators only, this consultation 

 of original sources was the most important matter; further- 

 more, the object was to select, from our whole knowledge of 

 nature, those matters which are essential to a world-view 

 based on knowledge of nature, or which have played an 

 important part in the development of this world-view. This 

 involved the omission of a vast amount of matter, of course 

 equally valuable as knowledge, but not bearing upon the 

 particular object in view. For the only person deserving 

 the name of a great scientist is he who has brought forward 

 something entirely new, having an essential bearing on our 

 knowledge of nature, on our view of the universe and on the 

 position of man in nature. The present book gives us the 

 opportunity to test whether, in spite of the limitation in the 

 number of workers dealt with, anyone is omitted, to whom 

 any single piece of knowledge of first rate importance can be 

 traced. For in the case of each investigator dealt with, all 

 new knowledge which we owe to him has been mentioned, or 

 at least referred to; and in spite of the small number of names, 

 we find that the whole of our knowledge of nature, as far as 

 it is of fundamental philosophical importance, is discussed. 

 The result is that we have at once a history of the develop- 

 ment of science, and a biographical account of the investi- 

 gators to whom scientific knowledge is due. 



The names of the most important and greatest investi- 

 gators, around whom our whole account is grouped, will be 

 found in the table of contents, arranged in order of time, and 

 with regard to the grouping of their main achievements; 

 they are chosen according to the originality and general 



