。Ilayitdownforaprinciple，thatthemomentsorquantitiesofmotioninbodiesareinadirectcompoundedreasonofthevelocitiesandquantitiesofMattercontainedinthem。
Hence，wherethevelocitiesareequal，itfollowsthemomentsaredirectlyasthequantityofMatterineach。Butitisfoundbyexperiencethatallbodiesbatingthesmallinequalities，arisingfromtheresistanceoftheairdescendwithanequalvelocity；themotionthereforeofdescendingbodies，andconsequentlytheirgravity，whichisthecauseorprincipleofthatmotion，isproportionaltothequantityofMatter；whichwastobedemonstrated。
。Youlayitdownasaself-evidentprinciplethatthequantityofmotioninanybodyisproportionaltothevelocity{242}andtakentogether；andthisismadeuseoftoproveapropositionfromwhencetheexistenceofisinferred。Prayisnotthisarguinginacircle？
。InthepremiseIonlymeanthatthemotionisproportionaltothevelocity，jointlywiththeextensionandsolidity。
。But，allowingthistobetrue，yetitwillnotthencefollowthatgravityisproportionalto，inyourphilosophicsenseoftheword；exceptyoutakeitforgrantedthatunknown，orwhateverelseyoucallit，isproportionaltothosesensiblequalities；whichtosupposeisplainlybeggingthequestion。Thatthereismagnitudeandsolidity，orresistance，perceivedbysense，Ireadilygrant；aslikewise，thatgravitymaybeproportionaltothosequalitiesI