Cha^. VII. ANTIENT METAPHYSICS. 433 



fides, there fliould be the lead tendency to' fly away from the 

 Centre. Again, if we fuppofc Mind to' be flie Moving Power, it i3 

 ftill more inconceivable, if poffible*: And, indeed, it appears to 

 liie fo inconceivable, that I cannot admit it, even by way of hypo- 

 thefiu, as I do the compofition of the Planetary Motion. Nor do I 

 think that any of Sir Ifaac's demonftrations in Aftronomy require 

 fach an hypothefis : For, as to his demonflration concerning the 

 Moon's Motion, I hope I have fliown, that nothing more is necef- 

 fary for it, than to fuppofe a defcent of the Moon in her Curvilineal 

 Motion as great, and governed by the fame laws, as if fhe fell down 

 perpendicularly. 



This notion of a Centrifugal Force, and all the other Propofitions 

 I have mentioned, appear to me to take their rife from one fource, 

 which is this, that none of the Mechanical Aftronomers, from Ga- 

 lileo down to the prefent times, appear to me to have had any idea 

 of the Motion by Mind : And, indeed, fince Geometry and Mecha- 

 nics came to be applied to the Motion of Bodies, they have been 

 confidcred as conftituting the whole Philofophy of Nature ; fo that 

 Geometry, inftead of being the handmaid of Philofophy, as the An- 

 tients confidered it, is become the miftrcfs, and a Geometer and 

 Philofopher are now fynonimous terms. 



To conclude, the principles of Sir Ifaac's Syftem of Aftronomy, 



as they have been hitherto explained, appear to me fo inconfiftent 



Vol. II. I i i with 



* The common illuftration that is given of the Centrifugal Force, is the Motion, 

 of a Stone in a Sling: But this is produced by a double aflion of Body upon the 

 Stone, firft, pufliing it forward by repeated Impu!."?, and then retaining it from 

 going forward ; which it is impofiible to apply to the Motion of the Planet. See 

 what i have further faid upon this fubjcft, p. 391, where, I think, I have accounted 

 for the Force with which the Stone, when it is let go, flies ofF. 



