Simultaneous Contrast: The Legacies of Hering and Helmholtz

"Thus if a pure white body is dotted with a dark-coloured paint by allowing small drops of the paint to fall on it, or if minute designs are made on it with this paint, the paint will look black or very dark; its distinctive quality will cease to be apparent and the eye will not be able to perceive its true colour. If marks are made with the same paint on a pitch-black body, the paint will look white or pale-coloured; its darkness will not be apparent and the eye will fail to perceive its true colour. If however, this paint is placed in the midst of bodies that are not extremely white or extremely black, its colour will appear as it is and the eye will perceive its true colour in so far as it can be perceived by sight .... For the qualities of lights and colours are perceived by the eye only by comparing them with one another" Alhazen, Optics, circa 1025 AD, from Sabra (1989a, volume I, page 99)