ARISTOTELIAN PHYSICS. C7 



empty, and therefore without a void there could be no motion : ami, 

 on the other hand, there is no void, for the interval between bodies 

 are filled with air, and air is something. These opinions had even 

 been supported by reference to experiment. On the one hand, Anax- 

 agorus and his school had shown, that air, when confined, resisted 

 compression, by squeezing a blown bladder, and pressing down an 

 inverted vessel in the water; on the other hand, it was alleged that a 

 vessel full of fine ashes held as much water as if the ashes were not 

 there, which could only be explained by supposing void spaces among 

 the ashes. Aristotle decides that there is no void, on such arguments 

 as this : 7 In a void there codd be no difference of up and down ; for 

 as in nothing there are no differences, so there are none in a privation 

 or negation ; but a void is merely a privation or negation of matter ; 

 therefore, in a void, bodies could not move up and down, which it is in 

 their nature to do. It is easily seen that such a mode of reasoning 

 elevates the familiar forms of language and the intellectual connections 

 of terms, to a supremacy over facts ; making truth depend upon 

 whether terms are or are not privative, and whether we say that 

 bodies fall naturally. In such a philosophy every new result of ob- 

 servation would be compelled to conform to the usual combinations of 

 phrases, as these had become associated by the modes of apprehension 

 previously familiar. 



It is not intended here to intimate that the common modes of ap- 

 prehension, which are the basis of common language, are limited and 

 casual. They imply, on the contrary, universal and necessary condi- 

 tions of our perceptions and conceptions ; thus all things are neces- 

 sarily apprehended as existing in Time and Space, and as connected 

 by relations of Cause and Effect ; and so for as the Aristotelian phi- t 

 losophy reasons from these assumptions, it has a real foundation, 

 though even in this case the conclusions are often insecure. We have 

 an example of this reasoning in the eighth Book, 8 where he proves 

 that there never was a time in which change and motion did not 

 exist ; " For if .all things were at rest, the first motion must have been 

 produced by some change in some of these things ; that is, there must 

 have been a change before the first change ;" and again, " How can 

 before and after apply when time is not ? or how can time be when 

 motion is not ? If," he adds, " time is a numeration of motion, and il 

 time be eternal, motion must be eternal." But he sometimes intro- 



Physic. Ausc. iv. 7, p. 215. Ib. viii. 1, p. 258 



