12 COSMOS. 



nature, (tiie telluric sphere of phenomena,) depend upon the 

 "unmoved motus of the universe." u The " ordaiuer" and the 

 ultimate cause of all sensuous changes must be regarded as 

 something non-sensuous and distinct from all matter. 17 Unity 

 in the different expressions of material force is raised to the 

 rank of a main principle, and these expressions of force are 

 themselves always reduced to motions. Thus we find already 

 in "the book of the soul" 18 the germ of the undulatory 

 theory of light. The sensation of sight is occasioned by a 

 vibration a movement of the medium between the eye and 

 the object seen and not by emissions from the object or 

 the eye. Hearing is compared with sight, as sound is like- 

 wise a consequence of the vibration of the air. 



Aristotle, while he teaches men to investigate generalities 

 in the particulars of perceptible unities, by the force of 

 reflective reason, always includes the whole of nature, and 



16 Aristot. Polit. vii. 4, p. 1326, and Metaph. xii. 7, p. 

 1072, 10 Bekk. and xii. 10, p. 1074-5. The pseudo- 

 Aristotelian work de Mundo, which Osann ascribed to Chry- 

 sippus (see Cosmos, vol. ii. p. 380) also contains (cap. 6, 

 p. 397) a very eloquent passage on the world-order -er and 

 world-sustainer. 



17 The proofs are collected in Ritter, History of Philosophy 

 (Bohn, 1838-46), Vol. 3, p. 180 et seq. 



18 Compare Aristot. de Anima, ii. 7 pag. 419. In this 

 passage the analogy with sound is most distinctly expressed ; 

 although in other portions of his writings Aristotle has greatly 

 modified his theory of vision. Thus in de Insomniis, cap. 2, 

 p. 459, Bekker., we find the following words : " It is evident 

 that sight is no less an active than a passive agent, and that 

 vision not only experiences some action from the air (the me- 

 dium), but itself also acts upon the medium." He adduces in 

 evidence of the truth of this proposition, that a new and very 

 pure metallic mirror will, under certain conditions, when 

 looked at by a woman, retain on its surface cloudy specks 

 that cannot be removed without difficulty. Compare also 

 Martin, Etudes sur le Timee de Platon. torn. ii. pp. 159-163. 



