XXV111 INTRODUCTION. 



establishment of one mere general truth furnishes 

 the proof of others less general which had been pre 

 viously reached by a different route ; often to mark 

 the diversities as well as resemblances of propo 

 sitions, and the particular circumstances upon 

 which these severally depend ; not rarely to note 

 in what way others had imperfectly obtained the 

 knowledge of these truths, or altogether had failed 

 to observe them ; frequently to find them deriving 

 new support from things afterwards brought to 

 light, and to see them explain phenomena subse 

 quently for the first time observed ; above all, to 

 see, and as we see to marvel how, beside those doc 

 trines, the teaching of which forms the main object of 

 the work, which are expounded with an exhaustive 

 fulness, and are at their first discovery established 

 in absolute perfection, so that scarce any addition 

 has, in the vast majority of instances, been found 

 either possible or required, there are also the 

 foundations laid of new discovery in other direc 

 tions, the rudiments provided of other systems, and 

 the very course plainly pointed out by which these 

 unthought of truths should in remote ages be 

 explored. 



On some few points differences of opinion having 

 arisen as to other men s claims to the discovery, 

 all controversial matters are purposely avoided. 

 But although it must be confessed that philoso* 



