Time, the Number of Movement

TIME, THE NUMBER OF MOVEMENT I T has been suggested that for our age the particular riddle the Sphinx has set is that of time. Many of the perennial 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 contingent 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 prominence this problem of time, but mathematical physics, presumably concerned with time, actually deals with its measurement 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." 1 The basic text for an understanding of the nature of time is Aristotle's Physics, Book Four, Chapter Ten, and the commentary 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." 2 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 numbering of motion and hence no time. Aristotle recognized this problem as a valid one: " Whether if soul did not exist time 1 Isaac Newton, Mathematical Principles of Natural Philosophy, Definitions: Scholium, trans. by Florian Cajori (Univ. of California Press, 1947), p. 6. 2 Aristotle, Physics, IV, c. 11, ~19bl-~. 481 482 SISTER M. JOCELYN would exist or not is a question that may fairly be asked, for if there cannot be someone to count, there cannot be anything that can be counted, so that evidently there cannot be number; for number is either what has been or what can be counted." 3 Would we, following the Aristotelian doctrine find ourselves forced to hold that prior to the creation of man (or at least of a higher animal with memory and hence a knowledge of time) there was no time and all things were instantaneous? We are cautioned against drawing too hasty a conclusion however by these words of Aristotle: " ... it is evident that every change and everything that moves is in time." 4 Certainly prior to the creation of man things changed and moved, so in Aristotle 's own words they were "in time." Such a conclusion however seems to contradict his position that if there were no soul there would be no time. There is some doubt however that this is truly Aristotle's position. The above translation is based on a text of William of Moerbeke. Aristotle's own text is an uncertain guide because it is in such poor condition and because the critical study of it is rendered uncertain in that the introduction of a period or a comma, missing in the text, would change the meaning. After a brief survey of the history of the problem it will be the purpose of this paper to show that it is more in keeping with the thought of Aristotle to hold that time is formally a being of nature and not of reason. True, the greater number of philosophers think that time would not be if there were no soul. We shall try to show that it is the thought of Aristotle and of St. Thomas that time is an ens naturae and not an ens rationis, and to exist even if there were no soul; not indeed perfect in being, but rather imperfect, as in motion. An investigation of the history of the question shows that without doubt Plato believed time to be real: Now the nature of the ideal being...