INTRODUCTION. 13 



to ultimate principles (the elements, as "it were, of the ele 

 ments), Plato exclaims, with modest diffidence, " God alone, 

 and those whom he loves among men, know what they are." 

 Such a mathematical mode of treating physical phenomena, 

 together with the development of the atomic tlieor}^ and the 

 philosophy of measure and harmony, have long obstructed the 

 development of the physical sciences, and misled fanciful in- 

 quirers into devious tracks, as is shown in the histoiy of the 

 physical contemplation of the universe. *' There dwells a 

 captivating charm, celebrated by all antiquity, in the simple 

 relations of time and space, as manifested in tones, numbers, 

 and lines."* 



The idea of the harmonious government of the universe re- 

 veals itself in a distinct and exalted tone throughout the writ- 

 ings of Aristotle. All the phenomena of nature are depicted 

 in the Pliysical Lectures (^Auscultationes PliysiccE) as mov- 

 ing, vital agents of one general cosmical force. Heaven and 

 nature (the telluric sphere of phenomena) depend upon the 

 " unmoved motus of the universe."! The " ordainer" and the 

 ultimate cause of all sensuous changes must be regarded as 

 something non-sensuous and distinct from aU matter. $ Unity 

 in the dilierent 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"§ the germ of the undulatory theory 

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



* Cosmos, vol. ii., p. 3ol, note. Compare also Gruppe, Ueber dit 

 Fragmente des Arcliytas, 1840, s. 33. 



t Aristot.,Po/^■^,vii.,4,p. 13-26,audi^/e^fi'^A.,xii.,7,p. 1072, 10, Bekk.. 

 and xii., 10, p. 1074-5. The pseudo-Aristoteliau work, De Mundo, 

 which Osaiin ascribed to Chrysippus (see Cosmos, vol. ii., p. 28, 29), 

 also contains (cap. 6, p. 397) a very eloquent passage on the world-or- 

 derer and world-snstainer. 



X The proofs are collected in Eitter, History of Philosophy (Jiohn, 

 1838-46), vol. iii., p. 180, et seq. 



§ Compare Aristot., De Anima, ii., 7, p. 419. lu this passage the 

 analogy with sound is most distinctly expressed; although in other por- 

 tions of his writings Ai-istotle 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 expenences some action from the air 

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

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

 tallic mirror will, under certain conditions, when looked at by a woman, 

 retain on its surface cloudy specks that can not be removed withoul 

 difficulty. Compare also Martin, Etudes sur le Timie de Platan., torn 

 ii. p, 159-.163. 



