of univerſals. the conſtitution of particular things is known by observations and experiments; and when that is done, it is by this rule that we judge univerſally of the nature of ſuch things in general.
Since then all bodies, whether upon Earth or in the Heavens, are heavy, ſo far as we can make any experiments or obſervations concerning them; we muſt certainly allow that gravity is found in all bodies univerſally. And in like manner as we ought not to ſuppoſe that any bodies can be otherwiſe than extended, moveable or impenetrable; ſo we ought not to conceive that any bodies can be otherwiſe than heavy. The extenſion, mobility and impenetrability of bodies become known to us only by experiments; and in the very ſame manner their gravity becomes known to us. All bodies we can make any obſervations upon, are extended, moveable and impenetrable; and thence we conclude all bodies, and thoſe we have no obſervations concerning, to be extended and moveable and impenetrable. So all bodies we can make obſervations on, we find to be heavy; and thence we conclude all bodies, and thoſe we have no obſervations of; to be heavy alſo. If any one ſhould ſay that the bodies of the fixed Stars are not heavy becauſe their gravity is not yet obſerved; they may ſay for the ſame reaſon that they are neither extended, nor moveable nor impenetrable, becauſe theſe affections of the fixed Stars are not yet obſerved. In ſhort, either gravity muſt have a place among the primary qualities of all bodies, or extenſion, mobility and impenetrability muſt not. And if the nature of things is not rightly explained
by the gravity of bodies, it will not be
