On The Heavens   

reverse motions on the complete circumference contraries. Nor again

can motion along the circle from A to B be regarded as the contrary of

motion from A to C: for the motion goes from the same point towards

the same point, and contrary motion was distinguished as motion from a

contrary to its contrary. And even if the motion round a circle is the

contrary of the reverse motion, one of the two would be ineffective:

for both move to the same point, because that which moves in a circle,

at whatever point it begins, must necessarily pass through all the

contrary places alike. (By contrarieties of place I mean up and

down, back and front, and right and left; and the contrary oppositions

of movements are determined by those of places.) One of the motions,

then, would be ineffective, for if the two motions were of equal

strength, there would be no movement either way, and if one of the two

were preponderant, the other would be inoperative. So that if both

bodies were there, one of them, inasmuch as it would not be moving

with its own movement, would be useless, in the sense in which a

shoe is useless when it is not worn. But God and nature create nothing

that has not its use.



5



This being clear, we must go on to consider the questions which

remain. First, is there an infinite body, as the majority of the

ancient philosophers thought, or is this an impossibility? The

decision of this question, either way, is not unimportant, but

rather all-important, to our search for the truth. It is this

problem which has practically always been the source of the

differences of those who have written about nature as a whole. So it

has been and so it must be; since the least initial deviation from the

truth is multiplied later a thousandfold. Admit, for instance, the

existence of a minimum magnitude, and you will find that the minimum

which you have introduced, small as it is, causes the greatest