MOVEMENT OF ANIMALS, iii. 



since they have no magnitude and are only ex- 

 tremities and points. For besides the fact that 

 nothing of this kind has any substance, it is also im- 

 possible for a single movement to be started by a dual 

 agency ; and they represent the poles as two. From 

 these considerations one may hazard the suggestion 

 that there is something which stands in the same 

 relation to Nature as a whole as the earth stands to 

 the animals and the things which are moved through 

 them.« 



Now those who in the fable represent Atlas as hav- 

 ing his feet planted upon the earth would seem to 

 have shown sense in the story which they tell, since 

 they make him as it were a radius, twisting the 

 heaven about the poles ; it would be a logical account, 

 since the earth remains still. But those who hold 

 this view must declare that the earth is no part of the 

 universe ; and, further, the force of that which causes 

 the motion and the force of that which remains still 

 must be equal. For there must be a certain amount 

 of force and strength in virtue of which that which 

 remains still remains still, just as there is a force in 

 virtue of which that which causes motion causes 

 motion ; and there is of necessity a similar proportion 

 between absences of motion as there is between 

 opposite motions, and equal forces are unaffected by 

 one another, but are overmastered by a superiority. 

 Therefore Atlas, or whatever else it is of like kind 

 within that causes motion, must not exert any pressure 

 which is too strong for the equihbrium of the earth ; 

 or else the earth will be moved away from the centre 

 and her proper place. For as that which pushes 

 pushes, so that which is pushed is pushed, and in 

 exact proportion to the force exerted ; but it creates 



449 



