Z8 ^ VI8inertiae I

spect to A moving with the velocity i Cj os jtheir relative velocities are equal. If we con- Iceivetwo men riding, the one after the other, Iand equally fast, they are relatively at rest, asif they were both standing still (o) j since thedistance between them is al ways the fame. It .is the fame thing as if they were both card- j'ed in a {hip with that celerity, and the famedistance between them.

XX. Therefore, if we would at any time ;silence all our doubts about the inactivity of fmatter, and be practically convinced of its re- jsi stance to all change of its state, we need only {call to mind that force or moment y in it to a$ !m other matter , is only thesum of all theforcesimpressed upon it ab extra (that is by fame im- $material Being, N° 14 and 15.) to overcome >its res fiance to motion- y and retained by it , be - \cause of its farther resistance to change the slate jit is thus put into. And hence, as was asierted ■)N° 16. since matter moving by gravity , at' :traction , elasticity , repulse , hath moment ° r ■force, it is a plain cafe it is resisting matter itsthese motions ; and that it is impelled in thew,by something without itself, or not matter >

(o). Xenophon long since observed this : Kal yelp e«v &I*''(pojifx T ?> tjia; dt ir^nXion yiyjiirxi C**irr.xira srai. Cjropttd.