rightly explained by their extenſion, mobility and impenetrability.
Some I know diſapprove this concluſion, and mutter ſomething about occult qualities. They continually are cavilling with us, that gravity is an occult property; and occult cauſes are to be quite baniſhed from philoſophy. But to this the anſwer is eaſy; that thoſe are indeed occult cauſes whoſe exiſtence is occult; and imagined but not proved; but not thoſe whoſe real exiſtence is clearly demonſtrated by obſervations. Therefore gravity can by no means be called an occult cauſe of the celeſtial motions; becauſe it is plain from the phenomena that ſuch a virtue does really exiſt. Thoſe rather have recourſe to occult cauſes; who ſet imaginary vortices, of a matter entirely fictious, and imperceptible by our ſenſes, to direct thoſe motions.
But ſhall gravity be therefore called an occult cauſe, and thrown out of philoſophy, becauſe the cauſe of gravity is occult and not yet diſcovered? Thoſe who affirm this, ſhould be careful not to fall into an abſurdity that may overturn the foundations of all philoſophy. For cauſes uſe to proceed in a continued chain from thoſe that are more compounded to thoſe that are more ſimple; when we are arrived at the moſt ſimple cauſe we can go no farther. Therefore no mechanical account or explanation of the moſt ſimple cauſe is to be expected or given; for if it could be given, the cauſe were not the moſt ſimple. Theſe moſt ſimple cauſes will you then call occult, and reject them? Then you muſt reject thoſe that immediately depend upon
them, and thoſe which depend upon theſe laſt,
