74 THE GREEK SCHOOL PHILOSOPHY. 



impressions and laws. In this application, the German philosophers 

 have, up to the present time, rested upon this distinction a great pail 

 of the TV eight of their systems ; as when Kant says, that Space and 

 Time arc the Forms of Sensation. Even in our own language, we 

 retain a trace of the influence of this Aristotelian notion, in the word 

 Information, when used for that knowledge which may be conceived 

 as moulding the mind into a definite shape, instead of leaving it a 

 mere mass of unimpressed susceptibility. 



Another favorite Aristotelian antithesis is that of Power and Act 

 (duvci^s, svs'p/eia). This distinction is made the basis of most of the 

 physical philosophy of the school ; being, however, generally intro- 

 duced with a peculiar limitation. Thus, Light is defined to be " the 

 Act of what is lucid, as being lucid. And if," it is added, " the lucid 

 be so in power but not in act, we have darkness." The reason of the 

 limitation, " as being lucid," is, that a lucid body may act in othei 

 ways ; thus a torch may move as well as shine, but its moving is not 

 its act as being a lucid body. 



Aristotle appears to be well satisfied with this explanation, for he 

 goes on to say, " Thus light is not Fire, nor any body whatever, or the 

 emanation of any body (for that would be a kind of body), but it is 

 the presence of something like Fire in the body ; it is, however, im- 

 possible that two bodies should exist in the same place, so that it is 

 not a body ;" and this reasoning appears to leave him more satisfied 

 with his doctrine, that Light is an Energy or Act. 



But we have a more distinctly technical form given to this notion. 

 Aristotle introduced a word formed by himself, to express the act 

 which is thus opposed to inactive power : this is the celebrated word 

 evreX^sia. Thus the noted definition of Motion in the third book 

 of the Physics, 21 is that it is " the Entelechy, or Act, of a movable 

 body in respect of being movable ;" and the definition of the Soul is 22 

 (hat it is " the Entelechy of a natural body which has life by reason of 

 its power." This word has been variously translated by the followers 

 of Aristotle, and some of them have declared it untranslatable. Act 

 and Action are held to be inadequate substitutes ; the very act, ipse 

 cursus actionis, is employed by some ; primus actus is employed by 

 many, but another school use primus actus of a non-operating form. 

 Budaeus uses efficacia. Cicero 23 translates it " quasi quandam continu- 

 atam motionem, et perennem ;" but this paraphrase, though it may 



Phys. iii. 1. ^ De Anima. ii. 1. TUSC. i. 10. 



