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“A drawing may represent a three-dimensional space, but the character of the drawing remains two-dimensional. Thus, the impression generated by a drawing is always dualistic: on the one hand, we perceive the image as three-dimensional, but we also perceive the play of lines in the two-dimensional plane. This dualism places drawing in a special category of art.”

– Lev Vygotsky, The Psychology of Art, 1922, p. 237