essential to Matter, &c. 59

and that the moment here, as elsewhere, isbut the aggregate of all these external impulsesimpressed upon it to overcome its resistance tobe moved with such a degree of celerity, andconserved in it, because of its constant fartherresistance to suffer any change of that presentstate ; and that, unless matter thus resisted achange of its state, and were impelled bysome force ab extra to change it, nobodywould be heavy; and elasticity or repulsionwould be without effect.

XXI. This also confirms what was said inN° 10, that unless matter resisted a change ofstate, the action of matter upon matter wouldbe inconceivable , or rather impossible. Forthere could have been no action where therewas no moment, or force, to act; and therecould have been no moment where there wasno resistance; since (to repeat it once again)from N» 19, it appears/Zw/ the moment of bo-dies is only their primitive refftance to-a changeoftheir fate multiplied by their celerity ; or theforce equal to that refftance , necessarily im-pressi'd on them to overcome it , and retained bythem. Let us fay then what would have beenthe result, if a body in motion had come uponother bodies at rest, and see if any consistent

effect