Chap. VII. ANTIEKT METAPHYSICS. 4jx 



pofition that never can be proved nor inferred, as I have iLown, hv 

 any juft analogy from the Motion of pther Bodies'^'. 



The laft propofition, of which I have endeavoured to difinciim- 

 ber the Newtonian Aftronomy, appears to me as extraordiuarv as 

 any I have hitherto mentioned. It is this, that every Body, that is 

 moved in a Curve, has a tendency to go off out of that Curve in 

 a Tangent ; and to this tendency they have given the name of Cen- 

 trifugal Force, which is a word much ufed by the Newtonians, more 

 now, I think, than formerly; nor do I know that Sir Ifaac has 

 ufed it at all, fpeaking of the Motion of a Planet in its Orbit: And 

 they have endeavoured to make a Science of it, by fljewing how it 

 ads in proportion to the fwiftnefs of the Motion in the Cui-ve, and the 

 diftance from the Centre f . Now, I would have the reader confider 

 attentively to what confequences this hypothefis leads. In the Jlr/i 

 place, it fuppofes, that a Body being once put in Motion, continues, 

 by its Vis Inftta^ to go on in a Straight Line to all eternity. This, 

 they fay, is in confequence of the Vis Iriertiae, or perfect paflivity 

 of Matter; — a propofition which, I think, I have fhown is ab- 

 folutely inconfiftent with the genuine principles of Theifm ; and, 

 accordingly, many of the Newtonians are not difpofed to afcribc 

 the continuance of the Motion to any Vis Itijita^ or Adtive Force, 

 in the Body, but to the Original Impulfe, which I hold is im- 

 pofFible to be true. But the Hypothefis of a Centrifugal Force 

 aflerts this Adive Power of Body in the ftrongeft manner ; for, 

 if there was nothing elfe in Body, but a Vis Inertiae^ or Vis 

 Pcrfcvcrantiae, as fome rather chufe to call it, by which it continues 

 in the ftate in which it is, whether of Motion or Reft, Why fhould 

 it net, after it is deflected from the Straight Line, continue in the 



new 



* Page 40c. 



^ See Montucla, above quoted, Vol. II. p. 408. 



