… theory is nothing more than practice carried on in the imagination.
This is from The New Landscape in Art and Science by Gyorgy Kepes (1956; 1967):
… When a figure is an irregular three-dimensional form — like the body of a human being — we are not confused or led astray by the shifting contour that never remains the same for a moment. We are made to see these endlessly changing aspects as persistent forms. In our heads, we build images of the moon, of animals, of trees, choosing from our remembered perceptions the contours which are significant to us. Perception of the boundary line enables man to populate his inner world with the forms and patterns which correspond to the outer world’s objects. He begins to understand relations with greater clarity, developing his capacity to control his environment.
Defining objects by shape was only one aspect of the role of line, just as separating a thing from its metamorphoses is only one aspect of perception. Once invented, the graphic line could assume a kind of independent life. The movement of the graphic tool across a surface could convey experience of movement and change, abstracting from perception of process and transformation.
[line break added] In the life of the stroke there was more than shape — motion and change were there as well. The growth of the line — its emergence from nothing, its speed, rhythm, length and directional changes — presented another key to the understanding of the world. And prehistoric man could not escape the magic impact of the suddenly emerging line.
Graphic recording of man’s inner linear visions was a high point in human inventiveness. Delineations stood for things just as verbal utterances did. Only slight further abstraction beyond the decisive elimination of interior details was needed to make a delineation stand for a word — and to invent writing.
… Useful crafts as well as graphic expression stirred ancient man to wonder. Under men’s hands, one substance miraculously became another; forms and patterns arose and grew; structure evolved and developed. Thus, theory was born.
Theory is born when practice becomes conscious, for theory is nothing more than practice carried on in the imagination. The techniques of tool and weapon making, weaving, basketry, ceramics and construction gave men models for thinking: association, dissociation, unity, rhythm, harmony, structure, shape, size, volume, motion, growth. As sensory images mainly, as words only partially and very primitively, these “ideas” became comprehensible.
[line break added] They assumed enormous generative force in raising human life to new levels of technical and intellectual accomplishment. Before priest and philosophers could conceive metaphysical questions of form and substance, permanence and change, or physical scientists laws of matter and motion underlying changes of state and composition, it was necessary that ancient man be moved to thought through his eyes and hands.
… Images shape and key our thoughts and feelings as the genetic material shapes and keys the composition, growth and reproduction of our bodies. The images we share encode our common culture; our private images encode our inner, unique lives, impressing on us both the richness of the sensed and the order of the understood.