( ) 
The Philofophy which Mr. Newton in his Principles and 
OpJiques has putfued is Experimental ; and it is not the Bu- 
finefs of Experimental Philofophy to teach the Caufes of 
things any further than they can be proved by Experiments. 
We are not to fill this Philofophy with Opinions which 
cannot be proved by Phaznomena. In this Philofophy Hy- 
pothefes have no place, unlefs as Conjedures or Queftions 
propofed to be examined by Experiments. For this ReafoiV 
Mr- Norton in his Optiques diftinguifhed thole things 
which weremade certain by Experiments from thofe things 
which remained uncertain, and which he therefore propofed 
in the End of his Optiques in the Form of Queries. For 
this Reafon, in the Preface to his Principles when he had 
mention’d the Motions of the Planets, Comets, Moon and 
Sea as deduced-in this Book from Gravity, he added .• Uti • 
nam cetera Nature Phenomena ex Principfis Mechanicis eodem 
argument andi genere derivare liceret • Nam mult a me movent 
ut nonnihil fufpicer ea omnia ex viribus quibufdam pender e po(fe , 
quibus corporum particuU per caufas nondum cognitas vel in fe 
mutuo impelluntur & fecundumjfguras regular es coherent, vel a f o 
invicem fugantur & recedunt quibus viribus igtiotis Fhilofophi 
haftenus Naturam fruflra tentarunt. And in the End of this 
Book in the feeond Edition, he faid that for want of a fuffi- 
cient Number of Experiments, he forbore to deferibe the 
Taws of the Adions of the Spirit or Agent by which this 
Attradion is performed-^ And for the fame Reafon he is 
filent about the Caufe of Gravity, there occurring no Ex- 
periments or Phenomena by which he. might prove what 
Was the Caufe. thereof. And this he hath abundantly de- 
clared in his Principles, near the Beginning thereof, in thefe 
Words; Virium caujas & fedes thecas jam non expendo. 
And a little after : Voces Attraftionis , Impulfus, vel Propenfto- 
nis cujufcunque in centrum in differ enter & pro fe mutuo promt [• 
cue ujurpo , has Vires non Phyf.ce fed Mttbematice tantum confde- 
undo. Unde caveat Left or ne per hujufmodi voces cogitet me 
i fpeciem * 
