TIME, THE NUMBER OF MOVEMENT 



IT has been suggested that for our age the particular riddle 

 the Sphinx has set is that of time. Many of the per- 

 ennial problems which torment the mind of man are more 

 or less involved with time; — to cite but one example: the 

 problem of man's free will and God's knowledge of future con- 

 tingent events. Though time is the measure of our duration and 

 of our activities, it is nevertheless far from clear. An object 

 is intelligible only in so far as it is in act. Upon investigation, 

 however, time seems to be more potential than actual. The 

 past is no longer, the future is not yet, and the only actuality, 

 the " now " is not time. 



Modern emphasis on physics has again brought into promi- 

 nence this problem of time, but mathematical physics, pre- 

 sumably concerned with time, actually deals with its measure- 

 ment rather than with its nature. This neglect by physicists 

 of the nature of time goes back to Newton who wrote: " I 

 do not define time, space, place, and motion, as being well 

 known to all." ^ 



The basic text for an understanding of the nature of time is 

 Aristotle's Physics, Book Four, Chapter Ten, and the com- 

 mentary on it by Saint Thomas Aquinas. Yet even his study 

 bristles with difficulties. One of these I have chosen as the 

 subject of this paper. Aristotle defines time as "... the 

 number of movement according to a before and an after." ^ 

 Thus he seems to put the formality of time in number. Now, 

 if time is a number and number depends on some mind, it 

 would seem that if there were no mind there could be no num- 

 bering of motion and hence no time. Aristotle recognized this 

 problem as a valid one: " Whether if soul did not exist time 



^ Isaac Newton, Mathematical Principles of Natural Philosophy, Definitions: 

 Scholium, trans, by Florian Cajori (Univ. of California Press, 1947), p. 6. 

 'Aristotle, Physics, TV, c. 11, 219bl-2. 



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