phase in which both appear to fall down to the position of the lower one.  It is not necessary to go further into details in order to demonstrate that the apparent movement is in no way the mere result of an afterimage and that the impression of motion is surely more than the mere perception of successive phases of movement.  The movement is in these cases not really seen from without, but is superadded, by the action of the mind, to motionless pictures.

The statement that our impression of movement does not result simply from the seeing of successive stages but includes a higher mental act into which the successive visual impressions enter merely as factors is in itself not really an explanation.  We have not settled by it the nature of that higher central process.  But it is enough for us to see that the impression of the continuity of the motion results from a complex mental process by which the various pictures are held together in the unity of a higher act.  Nothing can characterize the situation more clearly than the fact which has been demonstrated by many experiments, namely, that this feeling of movement is in no way interfered with by the distinct consciousness that important phases of the movement are lacking.  On the contrary, under certain circumstances we become still more fully aware of this apparent motion created by our inner activity when we are conscious of the interruptions between the various phases of movement.

We come to the consequences.  What is then the difference between seeing motion in the photoplay and seeing it on the real stage?  There on the stage where the actors move the eye really receives a continuous series.  Each position goes over into the next without any interruption.  The spectator receives everything from without and the whole movement which he sees is actually going on in the world of space without and accordingly in his eye.  But if he faces the film world, the motion which he sees appears to be a true motion, and yet is created by his own mind.  The afterimages of the successive pictures are not sufficient to produce a substitute for the continuous outer stimulation; the essential condition is rather the inner mental activity which unites the separate phases in the idea of connected action.  Thus we have reached the exact counterpart of our results when we analyzed the perception of depth.  We see actual depth in the pictures, and yet we are every instant aware that it is not real depth and that the persons are not really plastic.  It is only a suggestion of depth, a depth created by our own activity, but not actually seen, because essential conditions for the true perception of depth are lacking.  Now we find that the movement too is perceived but that the eye does not receive the impressions of true movement.  It is only a suggestion of movement, and the idea of motion is to a high degree the product of our own reaction. Depth and movement alike come to us in the moving picture world, not as hard facts but as a mixture of fact and symbol.  They are present and yet they are not in the things.  We invest the impressions with them. The theater has both depth and motion, without any subjective help; the screen has them and yet lacks them.  We see things distant and moving, but we furnish to them more than we receive; we create the depth and the continuity through our mental mechanism.