them all. I here uſe the word attraction in general for any endeavour, of what kind ſoever, made by bodies to approach to each other; whether that endeavour ariſe from the action of the bodies themſelves as tending mutually to, or agitating each other by ſpirits emitted; or whether it ariſes from the action of the æther or of the air, or of any medium whatſoever, whether corporeal or incorporeal, any how impelling bodies placed therein towards each other. In the ſame general ſenſe I uſe the word impulſe, not defining in this treatiſe the ſpecies or phyſical qualities of forces, but inveſtigating the quantities and mathematical proportions of them; as I obſervtd before in the definitions. In mathematics we are to inveſtigate the quantities of forces with their proportions conſequent upon any conditions ſuppoſed; then when we enter upon phyſics, we compare thoſe proportions with the phænomena of Nature; that we may know what conditions of thoſe forces anſwer to the ſeveral kinds of attractive bodies. And this preparation being made, we argue more ſafely concerning the phyſical ſpecies, cauſes, and proportions of the forces. Let us ſee then with what forces ſphærical bodies conſiſting of particles endued with attractive powers in the manner above ſpoken of muſt act mutually upon one another; and what kind of motions will follow from thence.
