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A VIS INERTIAE

and with another degree of velocity. Theone excludes the other. In a word, a bo-dy cannot have a tendency to change its pre-sent state, and at the same time a tendencynot to change it, more than two contradicto-ry propositions can both be true: for thesetwo are really such. This is a remarkableproperty of the resistance of matter, ‘That itis inconsistent with any power or force in it ;and should never be forgot by us. It infersmany notable consequences, which it seemswe are not sufficiently aware of at all times;and, among others, an utter impossibilitythat matter can ever become, by any pow-er, a living, self-moving substance ; seeing,as will appear, matter must resist all changeof its present state, as it is a solid substance.If this had been attended to, an infinity ofdoubting and disputing might have been sav-ed to mankind.

XVI. This will change our physicks alittle, and establish a new Theory of mat-ter. For it will follow that all gravity, at-traction, elasticity, repulsion, or whateverother tendencies to motion are observed inmatter, commonly called natural powers of

matter,