384 STUDIES IN SPECIAL SENSE PHYSIOLOGY 



but the coloured object existed in nature as a potential colour 

 before the act of vision and apart from it. " It is light that at once 

 transforms the potential colour to actuality and the potentially 

 seeing to an actually seeing eye " ( 7 ). 



In the colour scale (as among the elements) there is a sort of 

 opposition of positive and negative. White is the positive, black 

 the negative. 



This is Aristotle's general account of colour and of the "dia- 

 phanous" its vehicle omitting his views of reflection which are 

 not important from the physiological or psychological standpoint. 

 He also treats of certain colours in detail. 



The presence of some fire -like element is the cause of light in 

 the diaphanous, and in its absence we have darkness. In all de- 

 terminately bounded bodies we may assume something analogous 

 with the presence and absence of this fiery element. Its absence 

 means blackness, its presence whiteness. Therefore, in deter- 

 minately bounded bodies, blackness is privation of whiteness. 

 Thus, blackness and whiteness are contraries within one sensory 

 province, that of colour, and from them all the other colours are 

 to be explained. " The transition from white to black is possible 

 through continuous degrees of privation ; that from white to 

 black is likewise possible by an ascending scale in the opposite 

 direction. The various colours are species which fall between 

 the two contraries and are generated of certain combinations of 

 these " ( 8 ). For instance, in passing from white to black we first 

 come to crimson. As the intervening stages in the passage mark 

 relative extremes, change can start from any point. 1 



With regard to the actual mode of origin of the intermediate 

 colours, what is actually effected in the above-mentioned process ? 

 Aristotle discusses and condemns the doctrine of atomic juxta- 

 position and that of superposition, taking the view that a complete 

 blending occurred. No individual part of the compound colour 

 retains its primitive characters unmodified. 2 



As specific illustrations of this theory, we may take red, which 

 is produced by light streaming through black, and purple, distin- 

 guished from crimson in possessing more of the dark ingredient. 



1 Goethe, of coui'se, maintained the correctness of this theory in the Farbcn- 

 lehre. (Cf. Goethe's Theory of Colours, translated by Eastlake, London, 1840.) 



* Aristotle does not give this account in all his works. Vide Beare, op. cit., 

 pp. 74-76. 



