ATOM. 447 



"Quapropter locus est intactus, inane, vacansque. 

 Quod si non esset, nulla rations moveri 

 Res possent; nainque, officium quod corporis exstat, 

 OfEcere atque obstare, id in omni tempore adesset 

 Omnibus : baud igitur quicquam prooedere posset, 

 Principium quoniam cedendi nulla daret res." De Rerun, Natura, I. 335. 



The opposite school maintained then, as they have always done, that there 

 is no vacuum that every part of space is full of matter, that there is a 

 universal plenum, and that all motion is like that of a fish in the water, 

 which yields in front of the fish because the fish leaves room for it behind. 



"Cedere squamigeris latices nitentibus aiunt 

 Et liquidas aperire vias, quia post loca pisces 

 Linquant, quo possint cedentes confluere undse." I. 373. 



In modern times Descartes held that, as it is of the essence of matter to 

 be extended in length, breadth, and thickness, so it is of the essence of 

 extension to be occupied by matter, for extension cannot be an extension of 

 nothing. 



"Ac proinde si quaeratur quid fiet, si Deus auferat omne corpus quod in aliquo vase continetur, 

 et nullum aliud in ablati locum venire permittat? respondendum est, vasis latera sibi invicem hoc ipso 

 fore contigua. Cum enim inter duo corpora nihil interjacet, necesse est ut se mutuo tangant, at- 

 manifesto repugnat ut distent, sive ut inter ipsa sit distantia, et tamen ut ista distantia sit nihil ; 

 quia ouinis distautia est modus extensionis, et ideo sine substantia extensa esse non potest." 



Principia, n. 18. 



This identification of extension with substance runs through the whole of 

 Descartes's works, and it forms one of the ultimate foundations of the system 

 of Spinoza. Descartes, consistently with this doctrine, denied the existence of 

 atoms as parts of matter, which by their own nature are indivisible. He seems 

 to admit, however, that the Deity might make certain particles of matter 

 indivisible in this sense, that no creature should be able to divide them. These 

 particles, however, would be still divisible by their own nature, because the 

 Deity cannot diminish his own power, and therefore must retain his power of 

 dividing them. Leibnitz, on the other hand, regarded his monad as the ultimate 

 element of everything. 



There are thus two modes of thinking about the constitution of bodies, 

 which have had their adherents both in ancient and in modern times. They 

 correspond to the two methods of regarding quantity the arithmetical and the 

 geometrical. To the atomist the true method of estimating the quantity of 



