It is as if we were looking at a small plastic model of the landscape and in spite of our objective knowledge cannot recognize the flat pictures in the solid forms which we perceive.
It cannot be otherwise, because whenever in practical life we see an object, a vase on our table, as a solid body, we get the impression of its plastic character first of all by seeing it with our two eyes from two different points of view.

The perspective in which our right eye sees the things on our table is different from the perspective for the left eye.

Our plastic seeing therefore depends upon this combination of two different perspective views, and whenever we offer to the two eyes two such one-sided views, they must be combined into the impression of the substantial thing.

The stereoscope thus illustrates clearly that the knowledge of the flat character of pictures by no means excludes the actual perception of depth, and the question arises whether the moving pictures of the photoplay, in spite of our knowledge concerning the flatness of the screen, do not give us after all the impression of actual depth.
It may be said offhand that even the complete appearance of depth such as the stereoscope offers would be in no way contradictory to the idea of moving pictures.

Then the photoplay would give the same plastic impression which the real stage offers.