46 



Thus the riddle which oppressed these great 

 thinkers, from the lonians to Lavoisier, was in part 

 the nature of the "impetum faciens 1 " of the Bil- 

 dungstrieb. What makes the ball to roll ? Does 

 heart move blood or blood move heart ; and in 

 either case what builds the organ and what bestows 

 and perpetuates the motion? Albert of Cologne, 

 and at times even Aristotle, as we have seen, 

 were apt to leave moving things for abstract 

 motion, and to regard formulas as agents. Telesius 

 again, the first of the brilliant band of natural 

 philosophers in Italy of the xvith and xvnth 

 centuries, was still seeking this principle of nature 

 in the " form " of the peripatetics. Gilbert regarded 

 his magnetic force as " of the nature of soul, sur- 



1 Not only movement but also formative activity. The 

 rfjs Kivija-fcos is the efficient cause of Aristotle; for 

 him final causes direct motion the ov eve<a. Thus dialectic 

 was taken for dynamics. Even Kant confused cause and 

 effect with reason and consequence in hypothetical pro- 

 positions (Benn). Caverni (Storia del methodo sperimen- 

 tale in Italia, 1891 5) says that Jordanus Nemorarius (of 

 Borgentreich near Warburg, d. 1236) made the great advance 

 of extending the static physics of the ancients to establish 

 dynamics ; and that he introduced the word " moment." In 

 a cursory survey of the two works of Nemorarius which 

 we have in Cambridge I have not been able to verify this 

 statement ; the notion I have found but not the word itself. 



