314 APPENDIX. Chap. I. 



As I do not proff fs to be a great aftronomer or geometer, it is poffiBle 

 that I may haveerred in the analyfis I have given of the Planetary Mo- 

 tion ; and therefore 1 would nioft carneftly beg that thofe, Vv^ho are 

 more learned in geometry and aftronomy, would corred any errors 

 that I have fallen into, for which they fliall have my public thanks : 

 And I fhould be glad alfo to be informed by them, whether or not I 

 be right in fuppofing, that demonftration may not only be founded 

 upon fuch abftradions and feparations of things, which ncceiHuilj 

 exift to"-ether, as 1 have made in the cafe of the Planetary Motion, 

 but that there can be no fcience without fuch abftradions ; and, 

 further, v^hether 1 be not wrong in faying, that demonftration may 

 likewife be founded- upon an hypothefis, provided the hypothefis be 

 not abfurd or impoffible, as well as upon realities ; and that Sir 

 Ifaac himfelf has demonftrated in that manner. If I be right in 

 thefe particulars, the Newtonians, I think, muft confefs that they 

 are much obliged to me for having difmcumbered their fyftem of 

 fuch paradoxes, as That one Mind cannot move a Body in a circle or 

 cllipfis, but that there muft: be two Minds ading upon it in differ- 

 ent diredions, and counterading one another *. — That Mind, 

 though fo perfedly different in its nature from Body, can move Bo- 

 dy only in the fame way that Body moves Body, that is by exter- 

 nal impulfe, and therefore cannot vary the diredlion of it in every 

 inftant of the Motion — That the fame Motion, if produced by dif- 

 ferent caufes, would not have the fame properties, or be governed 

 by the fame laws. — That there is but one way of moti®n ceafmg, 

 that is by external obftrudion, and not by the ceafmg of the mo- 

 ving power to adt. — That there is only one way that Body can move 

 Body in the celeftial fpaces, that is by pulfion, but not by preffure 

 or trufion. — And, laft of all, that there is an innate and effential 

 power in Body, by which it can not only continue a Motion which 



has 



* See what I have faid upon this fubjefl, Vol. ii. p. 392. 393. 



