APPENDIX B 



A 



Vision. (26) Visi?hi. — Vision is effected in the following way (Be 

 anima II. 418 a 27 if.). There are three main factors : 

 Colour, the medium, and the sense-organ. 



" Colour " means " that which has the power to set in 

 movement that which is actually transparent " (to /car' 

 evepyeiav 8i,a(f>avds), and the latter acts as the medium. 

 The medium extends continuously from the object to the 

 sense-organ, and in its turn sets the sense-organ in 

 movement. The medium is indispensable, because 

 - colour cannot set the sense-organ in movement direct. 

 According to G.A. V. 780 b 34 ff., accuracy in seeing 

 distant objects depends upon the movement of the 

 medium not being dissipated, but " getting a direct 

 passage " {evOvnopeiv) ; indeed, the best results would 

 be obtained if there were a continuous tube between 

 the object and the eye (781 a 9). Compare the case 

 of Hearing, § 27. 



Examples of transparent media are Air, Water, and 

 "tertain solids. Their transparency is due not to them- 

 selves, but to the fact that they contain a certain sub- 

 stance which is also found in the " eternal substance of 

 the Upper Cosmos " (eV roi diSt'oi tu> avw awfian), i.e., in 

 the aither. Of this substance the actualization is Light ; 

 and its actualization is brought about by the agency 

 of Fire or something of a similar kind as the substance 

 of the Upper Cosmos — for this selfsame substance is 

 present in both." Thus Light is essential if vision is to 

 take place, because it is only when the substance in the 

 medium is actually (not merely potentially) transparent 

 that it can be set in movement by colour. 

 Hearing. (27) In the case of the other senses too a medium is indis- 

 pensable ; one example may suffice. In Hearing there 

 are again three main factors : the sounding object, the 

 Air, and the sense-organ. 



" A sounding object " {il)o<f>-qrt,K6v) means " an object 

 which can set in movement a continuous volume of Air 

 as far as the aKori " (the organ of hearing), and the 

 movement of the Air constitutes sound only when the 



n The obscurity of this sentence is due to Aristotle's text, not to my 

 presentation of it. 



590 



