92 



a moment or the new, it will be indivisible, and 

 the boundary of another time : for the now is not 

 only a beginning, but an end. There will there- 

 fore be time before A. Again : if B is the boun- 

 dary of time, if B is time, it may be divided to 

 infinity, and into the many boundaries which it 

 contains. But if B is the now, the same will also 

 be a beginning : for the now is not only a boundary, 

 but a beginning *. 



THEOREM 9. 



A motion which is naturally circular is perpetual. 



Demonstration. Let the circular motion be that 

 of the circle A B, I say that it is perpetual : for, 

 since time is perpetual, it is also necessary that 

 motion should be perpetual. And since time is 

 continued, (for there is the same now in the past 

 and present time,) it is necessary that there should 

 be some one continued motion : for time is the 

 number of motion. However, all other motions 

 are not perpetual : for they are generated from 

 contraries into contraries. A circular motion, 

 therefore, is alone perpetual : for to this, as we have 

 demonstrated, nothing is contrary. But that all 

 the motions which subsist between contraries, are 



* Hence the world is perpetual ; for it is consubsistent with 

 time. 



