XLV.
The Idea of Cause, modified into the conceptions of mechanical cause, or Force, and resistance to force, or Matter, is the foundation of the Mechanical Sciences; that is, Mechanics, (including Statics and Dynamics,) Hydrostatics, and Physical Astronomy. (iii. 1.)
XLVI.
The Idea of Cause is not derived from experience; for in judging of occurrences which we contemplate, we consider them as being, universally and necessarily, Causes and Effects, which a finite experience could not authorize us to do. The Axiom, that every event must have a cause, is true independently of experience, and beyond the limits of experience. (iii. 2.)
XLVII.
The Idea of Cause is expressed for purposes of science by these three Axioms:—Every Event must have a Cause:—Causes are measured by their Effects:—Reaction is equal and opposite to Action. (iii. 4.)
XLVIII.
The Conception of Force involves the Idea of Cause, as applied to the motion and rest of bodies. The conception of force is suggested by muscular action exerted: the conception of matter arises from muscular action resisted. We necessarily ascribe to all bodies solidity and inertia, since we conceive Matter as that which cannot be compressed or moved without resistance. (iii. 5.)
XLIX.
Mechanical Science depends on the Conception of Force; and is divided into Statics, the doctrine of Force preventing 14 motion, and Dynamics, the doctrine of Force producing motion. (iii. 6.)