 Bacon's theory of active or even vivid force in matter accounts for what he calls Cupid in De Principiis atque Originibus (Bacon V [1889], 463–5). Since his theory of matter aims at an explanation of the reality which is the substratum of appearances, he digs deeper than did the mechanistic physics of the 17th century (Gaukroger 2001, 132–7). Bacon's ideas concerning the quid facti of reality presuppose the distinction 