The impression of movement must therefore have other conditions than the actual performance of the movements, and above all it is clear from such tests that the seeing of the movements is a unique experience which can be entirely independent from the actual seeing of successive positions.

The eye itself gets the impression of a face at rest, and yet we see the face in the one case shrinking, in the other case swelling; in the one case every point apparently moving toward the center, in the other case apparently moving away from the center.

The experience of movement is here evidently produced by the spectator's mind and not excited from without.
We may approach the same result also from experiments of very different kind.

If a flash of light at one point is followed by a flash at another point after a very short time, about a twentieth of a second, the two lights appear to us simultaneous.

The first light is still fully visible when the second flashes, and it cannot be noticed that the second comes later than the first.