178 ADV^Jf CEMENT OF LEARNING. [bOOK IV. 



it is now known to be material, it becomes necessary to 

 inquire by what efforts so subtile and minute a breath can 

 put such gross and solid bodies in motion. Therefore, as 

 this part is deficient, let due inquiry be made concerning it. 



Sense and sensibility have been much more fully and 

 diligently inquired into, as well in general treatises upon the 

 subject as in particular arts ; viz., perspective, music, &c. ; 

 but how justly, is not to the present intention. And, there- 

 fore, WG cannot note them as deficient; yet there are two 

 excellent parts Avanting in this doctrine : one upon the 

 difference of perception and sense, and the other upon the 

 form of light. In treating of sense and sensibility, philo- 

 sophers should have premised the difference between per- 

 ception and sense, as the foundation of the whole : for we 

 find there is a manifest power of perception in most natural 

 bodies, and a kind of appetite to choose what is agreeable, 

 and to avoid what is disagreeable to them. Nor is this meant 

 of the more subtile perceptions only ; as when the loadstone 

 attracts iron, or flame flies to petreol, or one drop of water 

 runs into another ; or when the rays of light are reflected 

 from a white object, or when animal bodies assimilate what 

 is proper for them, and reject what is hurtful ; or when 

 a sponge attracts Avater, and expels air, &c. ; for in all cases, 

 no one body placed near to another can change that other, or 

 be changed by it, unless a reciprocal perception precede the 

 operation. A body always perceives the passages by which 

 it insinuates ; feels the impulse of another body, where it 

 yields thereto; j^erceives the removal of any body that with- 



to indicate its signification ; but Aristotle used it in distinct senses, 

 as signifying not only a simple act or function ot an unsubstantial 

 quality, but also as the act of a substantial power; and his followers have 

 never hit upon a generic term capable of uniting the two notions. Many 

 have abandoned it as untranslatable. Budseus uses the word eflBcacia ; 

 Cicero paraphrases it as a certain continuous and eternal motion (Tusc. 

 i. 10), which only implies the motion of unsubstantial qualities, to which 

 Bacon conf:?ied it. This signification, however, was but the exceptional 

 use of the term, and does not coincide with the genei-al applications of 

 it in the Greek schools. Hermonlaus Barbarus is said to have been so 

 much oppressed with this difficulty of translation, that he consulted the 

 evil spirit by night, entreating to be supplied with a more common and 

 familiar substitute for this word ; the mocking fiend, however, suggested 

 only a word equally obscure, and the translator disco;»tented with tluj^ 

 invented for himself the word perfectibilia. ^ 



