APPENDIX B 



(20) Now although in all these passages the heat seems to Dual 

 take the chief place, as it also seems to take the leading character 

 part in the formation of embryos. Aristotle says more ofi"^**"'"- 

 than once that the embryo is formed by means of cold as 



well as heat (see § 11 above; 743 a, 762 b 15, etc.). 

 And it would seem that pneuma really has a dual nature. 

 This is true of it when functioning as the instrument 

 of opeKTiKT] 'I'^XQi ^tI ^l^o when it is functioning as the 

 instrument of yewrfj-iicr] i/fvxrj (see § 10 above). Thus 

 {M.A. 702 a 10) the instrumental parts of the body can 

 change from solid to fluid, soft to hard, and vice versa, 

 and it is pneuina which brings about these changes. 

 Aristotle tells us (703 a 22) that pneuma contracts and 

 expands, and " has heaviness compared with fiery things 

 and lightness compared with the opposite things " ; 

 and that this power of contracting and expanding is 

 indispensable to it in view of the functions it has to 

 perform, because the actions of movement are pushing 

 and pulling. 



(21) De anima III. 433 b 18 ff. With further reference to Pneuma 

 pushing and pulling, Aristotle in a brief reference in the effects 



De anima to the De niotu states that " the instrument b'y p*,J^hing 

 used by ope^is in causing movement " is to be found and pulling, 

 where a beginning and an end coincide, e.g., at a ball- 

 and-socket joint : one remains at rest and the other is 

 moved : and the two though separable in definition are 

 not separable spatially ; for everjiihing gets moved by 

 pushing and pulling. (See also Phys. VII. 243 a 12 if.) 

 Compare too M.A. 703 a 12 : The "LYl stands in a 

 similar relation to the Soul-dpx^ ^s the point in a joint 

 (which /civet Kivov^ievov) stands to that which is unmoved. 



(22) There is a passage in the De caelo (IV. 301 b 20 ff.). Air as an 

 where again Aristotle is discussing the way in which instrument 

 movement is brought about, and although he is talking '°'' effecting 

 here of Air {a-qp) and not specifically of the kind of Air °i°^e™ent. 

 known as pneuma, the passage is apposite to our present 

 subject. Now of course according to Aristotle, some 



of the movement which takes place in the sublunary 

 world can be accounted for bj- his theory that the 

 " simple natural substances " Fire, Air, Water, Earth 

 have a " natural " movement (see App. .\ § 2). But 

 movement is also caused forcibly ; and force can either 



587 



