… If one sees on scales a pound of iron balancing a pound of feathers, one becomes involved in the experience …
This is from Language of Vision by Gyorgy Kepes (1944):
… A picture-surface becomes a vital spatial world, not only in the sense that the spatial forces are acting on it — moving, falling and circulating — but also in the sense that between these movements the field itself is charged with action. The actual visual elements are only the focal points of this field; they are the concentrated energy. Color, value, texture, point, line and area radiate different amounts of energy, and thus each element or quality can encompass a different radius of the picture-surface. These fields extend into every dimension and each field has its own unique form.
… Just as any force can be manifested only through resistance to an opposite force, so spatial forces may be perceived only as they meet opposing spatial forces. A random placing of spatial forces, point, line, area, will open the picture-plane, but because these forces are so haphazardly arranged, they will not reach a balanced constellation in which they are equal in strength and opposite in direction. The picture surface is made hollow; the two-dimensional background, the frame of reference in which the spatial movements can be measured is missing. The spatial vitality cannot reach full maturity.
If the forces and their induced fields are of equal optical quality and spatial strength, a balance will be reached, but it will be without tension, static and lifeless. If, however, one knows how to estimate the forces and their energy-field, he will be able to use such opposing fields so that each will balance the other on the picture-plane.
[line break added] A line or shape in a certain color and position will have a field opened and advancing toward the spectator; another unit will create a field in a receding direction; another will activate a field tending upward on the surface; and yet another, down. Those movements may be different in terms of their optical measures and qualities — that is, opposite in direction, weight, intensity — but, if they are equal in strength in terms of their spatial fields, a dynamic equilibrium will be reached on the picture surface.
If one sees on scales a pound of iron balancing a pound of feathers, one becomes involved in the experience because of the apparent optical contradiction in logic. One is forced to think about the nature of the opposing materials and grasp their further relationships. The sight of an adult balanced by a small child on a see-saw, because of their different distances from the center of gravity, induces a similar experience.