SPACE, TIME 311 



future with reference to one another. But if the events are 

 so situated that a message from one to the other would be 

 required to travel faster than light, causal influences could 

 not pass from one to the other. Two such events could have 

 no absolute time order; A might be contemporary with B, 

 A might precede B, or B might precede A, according to the 

 system of reference of the observer. Hence relativity insists 

 upon an absolute directional feature for time, but specifies 

 in what sense it applies to events and in what sense it does 

 not. 



REFERENCES 



E. W. Hobson, Domain of Natural Science (New York: Macmillan, 

 1923), Chap. VI. 



C. D. Broad, Scientific Thought (New York: Harcourt, Brace, 



1923), Chaps. I, II, XII. 

 H. Poincare, Foundations of Science (New York: Science, 1921), 

 Science and Hypothesis, Part II; Value of Science, Chap. II. 



D. H. Parker, Self and Nature (Cambridge: Harvard University, 



1917), Chaps. V, VII. 

 A. d'Abro, Evolution of Scientific Thought (New York: Boni and 



Liveright, 1927). 

 Bertrand Russell, Our Knowledge of the External World (Chicago: 



Open Court, 1915), lect. V. 

 A. N. Whitehead, Concept of Nature (Cambridge: Cambridge 



University, 1920), Chaps. Ill, IV, V. 



