Such being the teachings alike of general and of scientific experience, I can not but feel surprised that any persons claiming the title of philosophers should affirm that we know nothing except matter and motion, and that force is a creation of our own imagination. One might suppose such persons to be either destitute of the "force-sense," or to have based their philosophical system upon the movements of the heavenly bodies which they can only see, instead of upon those mundane phenomena in the cognition of which they can bring their hands to the assistance of their eyes. How essential this assistance is to the formation of correct conceptions of the solid forms and relative positions of the objects around us is known to every one who has studied the physiology of the senses. Should we not think it absurd on the part of any one who possesses in the use of his hands the means of detecting the error of his visual perceptions, if he were to base a superstructure of reasoning—still more to found a whole system of philosophy—upon the latter alone? Yet such appears to me to be the position of those who deny our direct cognition of force.
Let us suppose (if possible) a man who had enjoyed the full use of his eyes, but whose limbs had been completely paralyzed from infancy, looking on at a game of billiards. He would see a succession of motions connected by regular sequence—the motion of the arm of the player, the stroke of the cue, the roll of the ball, its contact with another ball, the movement of the second ball, the change of direction or the entire stop of the first, the rebound of balls from the cushion in altered directions, and so on. And he might frame a statement in "terms of motion" of all that passes before his eyes, thinking this all he can know. But suppose the limbs of such a man to be suddenly endowed with the ordinary powers of sensation and movement; let him take the cue into his hands and himself strike the ball; let him hold his hand on the-table so that the rolling ball shall strike it and make him feel its impact; let him hold the second ball and feel the shock imparted to it by the stroke of the first. Can any one deny that he would thus acquire a dynamical conception linking together the whole succession of phenomena, which he was previously quite incapable of forming; that this dynamical conception is quite as directly based upon the experience derived through his "force-sense" as his kinetic expression was upon that derived through his visual sense; and that this cognition of the force producing the motions is, therefore, fully as much entitled to be introduced into a logical doctrine of causation as the visual cognition of the motions themselves? If it be replied that we have no proof that the movement of the ball we strike is produced by the force which we consciously exert in striking it, I simply rejoin that we have as much proof of it as we have of anything which rests upon universal experience, and which we can verify experimentally as often as we choose to try—quite as much as we have of the existence of anything whatever that is external to ourselves.
