Drawing is vision on paper. More than that, it is individual vision, tied up with individual perception, interest, observation, character, philosophy, and a host of other qualities all coming from one source.
All the senses combine to give us intelligent perception. We have a sense of space or depth, even if we know nothing of the science of perspective. We are quickly aware of distortion or deformity, since the appearance does not coincide with what experience has taught us is normal or truthful. Form is registered in the mind, even if we know nothing of anatomy and proportion, so that we recognize a face immediately, though we could not give even a good verbal description of it. Our sense of proportion tells us that this is a child and that a [little person], or this a puppy and that a small dog. Intelligent perception includes a feeling for bulk and contour. We know a swan from a goose, or a goose from a duck. This trait is as well developed in those who look at art as it is in artists. We all as individuals have subconsciously accepted certain effects of light. We know when appearances are consistent with daylight, artificial light, twilight, or bright sunlight. Such perception is part of nature.
The minute a spectator sees change of proportion, distortion, change of form, color, or texture, he realizes some is wrong. The cleverest imitation will not fool him. The dummy in the department store window is a dummy to everyone. We know flesh from wax by the effects that have previously been registered in our minds... We artists cannot ignore this intelligent perception and expect to secure an intelligent response, or even a favorable response, to our work. Make up your mind that your audience will react to your work just as it does to life itself. Intelligent perception finds only truth convincing.
If what we say in paint is untrue, in color values or effect, the spectator feels it, and there is nothing we can do to convince him otherwise.
... all the visible world is only light on form.