20 THE FITNESS OF THE ENVIRONMENT 



But, however important such distinctions may 

 be for the philosopher, the man of science in 

 his practical task is obliged to put them 

 aside and to make the best of whatever evi- 

 dence experience, observation, and experi- 

 ment may supply. Out of such studies space 

 'and time have emerged, usefully defined by 

 mathematical criticism as substantial parts 

 of the edifice of science. 1 



There is no small difficulty in the exposi- 

 tion of modern critical results regarding 

 space and time, but fortunately there is little 

 need of considering them on the present 

 occasion. For in spite of all assaults of phi- 

 losophers and mathematicians space remains 

 for practical purposes more certainly than 

 ever the Euclidian space of the ancients, 

 only it has become somewhat richer in char- 

 acteristics. And time is now and forever 

 that which flows equably, wholly independ- 

 ent of all else, though almost all else is 

 dependent upon time. It is Euclidian space 

 in which the earth moves and describes its 

 ellipse, parallel rays of light never do meet 

 in our practical experience, and our crystals 



1 The works of Poincare, "La Science et l'Hypothese," "La 

 Valeur de la Science," and "Science et Methode," published 

 by Flammarion, may be consulted for a popular statement of 

 such mathematical studies. 



