In ordinary visual perception, we see by means of light; we distinguish by means of reflected and refracted colors. But in ordinary perception, this medium of color is mixed, adulterated. While we see, we also hear; we feel pressures, and heat and cold. In a painting, color renders the scene without these alloys and impurities. They are part of the dross that is squeezed out and left behind in an act of intensified expression. The medium becomes color alone, and since color alone must now carry the qualities of movement, touch, sound, etc., that are present physically on their own account in ordinary vision, the expressiveness and energy of color are enhanced.