APPENDIX B 



accelerate natural movement {e.g., it can make a stone go 

 downwards more quickly than it would do naturally) or 

 it can produce movement contrary to Nature {e.g., it can 

 make a stone go upwards) ; it is in fact the sole source 

 of unnatural movement. And in either case it uses Air 

 as its instrument {wanep opydvM XPV^"-'- '''*? o-epi), because 

 Air is naturally/ constituted to be light and heavy {'rre(f>vKe 

 Kal Kov<f>os elvai kou. jSapuj) ; the Air, qua light, will cause 

 an object to be carried upwards, for the Air gets pushed 

 and receives the dpxTJ from the force which is exerting 

 itself; qua heavy, it will cause the object to be carried 

 downwards : the force " as it were hitches the movement 

 on to {iva<j>ailiaaa) the Air''' and so transmits it to the 

 object in either case. Hence an object which is set 

 moving forcibly {i.e., contrary to Nature) continues 

 travelling although that which set it moving does not 

 follow it up ; and if there were no such physical sub- 

 stance as Air there could be no such thing as enforced 

 movement." In the same way, says Aristotle, Air gives 

 a fair wind to {avveTrovpiCei), helps on, natural movement. 

 Dual char- (23) This dual nature of Air is not really so surprising as it 

 acter of Air. sounds at first hearing, for {jDe caelo IV. 31 1 b 5 flF.) all 



the physical substances possess heaviness except Fire, 

 and they all possess lightness except Earth. In its own 

 place, each possesses heaviness, even Air ; thus, except 

 in Water and Earth, Air possesses heaviness. At 

 312 a 12 ff. Aristotle lays down that the distinction of 

 " form " and " matter " is to be found in the category 

 of " place " as well as in the categories of " quality " 

 and " quantity " : thus, to dvai belongs to the deter- 

 minate, TO KOLTCj belongs to " matter." And taking the 

 special instance of the " matter " of " the heavy and 

 light," qua potentially X it is the matter of the heavy, 

 qua potentially Y it is the matter of the light : it is the 

 same " matter," but its ehau is not the same {cf. 310 b, 

 311 a). 

 (24) For the important role of Air as a medium between the 

 objects which give rise to sensations and the sense-organ, 



« It should be remembered that according to Aristotle nothing can 

 exert any effect upon ("move") another thing unless it is in contact 

 with it; see Phys. II. 244 a, b, and O.A. II. 734 a 3. That is why the 

 movement must be "hitched on" to the Air; cf. H.A. VII. 586 a 17 



ovSev yap ptTTxetTat noppoi apev ^tas jri'euju.aTtKrjs. 



588 



