§ 64. The conception of Motion as presented or represented in the developed consciousness, involves the conceptions of Space, of Time, and of Matter. A something that moves; a series of positions occupied in succession; and a group of co-existent positions united in thought with the successive ones—these are the constituents of the idea. And since, as we have seen, these are severally elaborated from experiences of _force_ as given in certain correlations, it follows that from a further synthesis of such experiences, the idea of Motion is also elaborated. A certain other element in the idea, which is in truth its fundamental element, (namely, the necessity which the moving body is under to go on changing its position), results immediately from the earliest experiences of force. Movements of different parts of the organism in relation to each other, are the first presented in consciousness. These, produced by the action of the muscles, necessitate reactions upon consciousness in the shape of sensations of muscular tension. Consequently, each stretching-out or drawing-in of a limb, is originally known as a series of muscular tensions, varying in intensity as the position of the limb changes. And this rudimentary consciousness of Motion, consisting of serial impressions of force, becomes inseparably united with the consciousness of Space and Time as fast as these are abstracted from further impressions of force. Or rather, out of this primitive conception of Motion, the adult conception of it is developed simultaneously with the development of the conceptions of Space and Time: all three being evolved from the more multiplied and varied impressions of muscular tension and objective resistance. Motion, as we know it, is thus traceable, in common with the other ultimate scientific ideas, to experiences of force. That this relative reality answers to some absolute reality, it is needful only for form’s sake to assert. What has been said above, respecting the Unknown Cause which produces in us the effects called Matter, Space, and Time, will apply, on simply changing the terms, to Motion. * * * * *