In his comprehensive work; Zur Farbenlehre, Goethe also included a history of studies on color. There one finds that he had aquainted himself thoroughly with color science all the way from antiquity, through the middle ages, to Kepler, Descartes etc. The idea that light and darkness both play a major role in the formation of natural phenomena was already known for instance in ancient Greece, Middle East and Egypt. Goethe was well aware of this, so the idea itself must not have been new to him when he glanced through the prism for the first time. One cannot say, however, that Goethe used this idea as a theoretical hypothesis behind his obsevational work. What it provided was an open mind towards observable reality, a non discriminative and impartial attitude towards all sense experience.