MOVEMENT OF ANIMALS, iv. 



do not really exist, but there is a possibility of 

 their existing (for an infinite motive force " is impos- 

 sible because an infinite body is also impossible), 

 it would be possible for the heaven to be dissolved. 

 For what is there to prevent this happening if it 

 is not impossible ? And it is not impossible, unless 

 the opposite proposition is inevitable. But let us 

 leave the discussion of this question for another 

 occasion.^ 



Must there, then, or must there not, be something 

 immovable and at rest outside that which is moved 

 and forming no part of it ? And must this be true 

 also of the universe ? For it would perhaps seem 

 strange if the origin of motion were inside. And so 

 to those who hold this view Homer's words w^ould 

 seem appropriate : 



Nay, ye could never pull down to the earth from the 



summit of heaven, 

 Zeus, the highest of all, no, not if ye toiled to the utmost. 

 Come, ye gods and ye goddesses all, set your hands to 



the hawsers.* 



For that which is entirely immovable cannot be 

 moved by anything. And it is here that we must 

 look for the solution of the problem stated some time 

 ago, namely, whether it is possible or impossible for 

 the composition of the heaven to be dissolved, seeing 

 that it depends upon an origin which is immovable. 



Now in the animals there must exist not only that 

 which is immovable in this sense,** but there must 

 also be something immovable in the actual things 

 which move from place to place and which themselves 



<= Iliad viii. 20-22. The lines are quoted in the wrong 

 order and the textits receptus reads iJ.-qaTwp' for Travruv. 



^ i.e. something immovable and at rest which is outside 

 that which is moved and forms no part of it (c/. 699 b 32). 



453 



