Vital and Physical Motion. i 1 5 



moving thing was supposed to be possessed at the 

 time. 



Hippocrates believed in the universal presence of a 

 living, intelligent, active principle, to which he gave the 

 name of nature ( covert?), and to him, as to many in the 

 present day, it was enough to refer motion to nature to 

 regard it as natural. The power of motion, indeed, was 

 one of the faculties with which the principle of nature 

 was endowed. 



Plato says little to the point. With him science 

 merged in philosophy and theology ; to him vital motion, 

 and motion generally, when traced to its source, resolved 

 itself into a display of divine power. 



Aristotle, the great contemporary of Plato, recog- 

 nized, not a Divine Being as Plato did, but a First 

 Moving Cause, a primum mobile, one in essence, eternal, 

 immaterial, at once immoveable, and the spring of all 

 movement. According to him, this First Moving Cause 

 worked in the living body ((woi>) through the instrumen- 

 tality of a principle which was distinctive of this body, 

 and to which he gave the name of soul (^v^)- a prin^- 

 ciple possessing various energies or faculties of its own, 

 distinct from the organs in which it was manifested, and 

 yet requiring these organs for its manifestations. To 

 this soul, when most developed, belonged several faculties 

 (&vra/i6t9) the faculty of receiving nourishment (Svra/^? 

 BpeTTTiKij), the faculty of sensation (8. ai<rdr)TiKij), the 

 faculty of motion in place (8. Ktvrrriicij), the faculty of 

 impulse or desire (8. operucj), the faculty of intelligence 

 (S. Siavovriicri). Vegetables even, by having the lowest 

 of these faculties, the threptic, were supposed to haye 

 souls. Moreover, it is hinted that the seat of this kinetic 

 faculty in animals is in the muscles, and that a conjec- 

 ture for which Praxagoras, who lived two hundred years 



I 2 



