OF NATURAL PHILOSOPHY. Ill 



Of course there will occur a limit beyond \vhich 

 it is useless for merely human faculties to enquire ; 

 but where that limit is placed, experience alone can 

 teach us ; and at least to assert that we have attained 

 it, is now universally recognized as the sure criterion 

 of dogmatism. 



(102.) In the early ages of the church the writ- 

 ings of Aristotle were condemned, as allowing too 

 much to reason and sense ; and even so late as* the 

 twelfth century they were sought out and burned, 

 and their readers excommunicated. By degrees, 

 however, the extreme injustice of this impeachment 

 of their character was acknowledged : they became 

 the favourite study of the schoolmen, and furnished 

 the keenest weapons of their controversy, being 

 appealed to in all disputes as of sovereign autho- 

 rity ; so that the slightest dissent from any opinion 

 of the " great master," however absurd or unin- 

 telligible, was at once drowned by clamour, or 

 silenced by the still more effectual argument of 

 bitter persecution. If the logic of that gloomy 

 period could be justly described as " the art of talking 

 unintelligibly on matters of which we are ignorant," 

 its physics might, with equal truth, be summed up 

 in a deliberate preference of ignorance to knowledge, 

 in matters of every day's experience and use. 



(103.) In " this opake of nature and of soul," 

 the perverse activity of the alchemists from time 

 to time struck out a doubtful spark*; and our 



* Macquer justly observes, that the alchemists would have 

 rendered essential service to chemistry had they only related 

 their unsuccessful experiments as clearly as they have obscurely 

 related those which they pretend to have been successful.-* 

 Macquer's Dictionary of Chemistry, i. x. 



