154 Notes, ii. i. 



11. It was a disputed questiqn whether the passive agent must be s'imilar or dissimilar 

 to the active agent ; the former being the opinion of Democritus, the latter the general . 

 view. Aristotle says both opinions are partly true, partly false. "The active and the 

 passive agents cannot be absolutely similar ; for if so each object would move itself, and 

 everything would bain perpetual motion. Neither can they be utterly dissimilai; For 

 how can two such essentially distinct things as whiteness and a line affect each other ? 

 Whiteness indeed and a coloured line can affect each other ; but this is in virtue of their 

 generical resemblance, both having colour. So also a savour cannot affect a colour, nor 

 a colour a savour; but -one savour aff'ects another savour, one colour another colour. 

 The result then is that the passive and the active agents are generically one, but 

 specifically distinct " (Z>. G. et C. i. 7). 



12, The ancients agreed in assigning each separate sense to a separate element, but 

 differed from each other in their distribution, some, as Plato, coupling vision with fire, 

 others, as Democritus, with water. '' It is plain that we must attach each one of the 

 sense-organs to one of the elements. The optical part of the eye we must take to 

 be of water. The part of the ear which is sensitive to sound we must take to be of 

 air. Smell we must take to be of fire ; for a smell is a kind of smokelike ascent of 

 vapour, and such comes from fire. The organ which is sensitive to touch we must take 

 to be of earth, and taste is but a variety of touch " {De Sensu, 2, 18). 



From the passage paraphrased in the last note it appears that A, held that nothing 

 could be set in motion excepting by a motor agent homogeneous with itself. Now in 

 sensation " the object of sense sets the medium in motion, and then the motion of the 

 medium is communicated to the sense organ " {D. A. ii, 7). In order then for this 

 communication to be possible the medium and the sense organ must be homogeneous 

 with each other, " The medium of sound is clearly air ; the ear then must be of this 

 element. The eye must be of water, because to water animals the medium of sight is 

 water, and though to land animals air is the medium, it is so not in its character of air, 

 but in its character of transparent substance. The organ of touch, which lies in or close 

 to the heart, must be of earth, because the flesh which is earthy is the medium of touch 

 (ii. 8, Note 2), and taste goes with touch, being only a variety^ of it (ii. 10, Note 22). 

 The organ of smell must be of fire," partly because this is the only remaining element, 

 and also "because the medium of smell seems to be of fire, a smell being a kind of smoke- 

 like exhalation which occurs in a fiery medium " {De Sensu, 2). There is plainly in 

 the above a difficulty as regards eye and vision. The element air has already been 

 assigned to the ear, and the hypothesis requires each sense organ to be coupled with 

 a distinct element. It is necessary therefore to say the eye is of water, although air is 

 the usual medium of sight ; and doubtless the presence of so much fluid in the eye, 

 and the case of water animals, seemed to corroborate this view. But clearly the 

 explanation that air acts as well as water not in its character of element but of transparent 

 substance is inconsistent with the original hypothesis. 



The foregoing will serve to show what the ancients meant in connecting each sense 

 with a separate element. But it seems at least doubtful whether A. himself held 

 this doctrine. In the text he speaks only of others holding it, not of himself. It is 

 true the passage quoted above from the De Sensu expressly adopts the doctrine. But 

 there are sti-ong grounds for believing that passage to have been interpolated ; seeing 

 that in it smell is said to be "a smokelike exhalation from fire," while very shortly 

 afterwards in the same treatise A. says that this view is held by some but is an error, 

 which he proceeds to refute. His own opinion as to the media, so far as can be gathered 

 from the scanty data- forthcoming, seems to have been as follows. Air and water form 



