Or, shall we take another proof, still more convincing.

This is the vibratory and silent movement which is invoked by physicists to explain the peculiarities of subjective sensation; so that the interferences, the pulsations of sound, and, in fine, the whole physiology of the ear, is treated as a problem in kinematics, and is explained by the composition of movements.
What kind of reality do physicists then allow to the displacements of matter?
Where do they place them, since they recognise otherwise that the essence of matter is unknown to us?
Are we to suppose that, outside the world of _noumena_, outside the world of phenomena and sensations, there exists a third world, an intermediary between the two former, the world of atoms and that of mechanics?
A short examination will, moreover, suffice to show of what this mechanical model is formed which is presented to us as constituting the essence of matter.

This can be nothing else than the sensations, since we are incapable of perceiving or imagining anything else.

It is the sensations of sight, of touch, and even of the muscular sense.
Motion is a fact seen by the eye, felt by the hand; it enters into us by the perception we have of the solid masses visible to the naked eye which exist in our field of observation, of their movements and their equilibrium and the displacement we ourselves effect with our bodies.
Here is the sensory origin, very humble and very gross, of all the mechanics of the atoms.

Here is the stuff of which our lofty conception is formed.