PREFACE. 5 



what is light and tumid, but sunk what was ponderous and 

 solid. As to those who have set up for teachers of the sciences, 

 when they drop their character, and at intervals speak their 

 sentiments, they complain of the subtilty of nature, the 

 concealment of truth, the obscurity of things, the entangle 

 ment of causes, and the imperfections of the human under 

 standing ; thus rather choosing to accuse the common state 

 of men and things, than make confession of themselves. It is 

 also frequent with them to adjudge that impossible in an art, 

 which they find that art does not affect ; by which means they 

 screen indolence and ignorance from the reproach they merit. 

 The knowledge delivered down to us is barren in effects, 

 fruitful in questions, slow and languid in improvement, ex 

 hibiting in its generalities the counterfeits of perfection, but 

 meagre in its details, popular in its aim, but suspected by its 

 very promoters, and therefore defended and propagated by 

 artifice and chicanery. And even those who by experience 

 propose to enlarge the bounds of the sciences, scarce ever 

 entirely quit the received opinions, and go to the fountain- 

 head, but think it enough to add somewhat of their own ; 

 as prudentially considering, that at the time they show their 

 modesty in assenting, they may have a liberty of adding. 

 But whilst this regard is shown to opinions and moral 

 considerations, the sciences are greatly hurt by such a languid 

 procedure ; for it is scarce possible at once to admire and 

 excel an author : as water rises no higher than the reservoir 

 it falls from. Such men, therefore, though they improve 

 some things, yet advance the sciences but little, or rather 

 amend than enlarge them. 



There have been also bolder spirits, and greater geniuses, 

 who thought themselves at liberty to overturn and destroy 

 the ancient doctrine, and make way for themselves and their 

 opinions ; but without any great advantage from the dis 

 turbance ; as they did not effectively enlarge philosophy and 

 arts by practical works, but only endeavoured to substitute 

 new dogmas, and to transfer the empire of opinion to them 

 selves, with but small advantage ; for opposite errors proceed 

 mostly from common causes. 



As for those who, neither wedded to their own nor others 

 opinions, but continuing friends to liberty, made use o. 

 assistance in t]ieir inquiries, the success they met witji di(J 



