Nothing is more simple. Take a landscape with a cloudy sky, which means diffused light in the old sense of the term, and observe the effect upon it of a sudden burst of sunlight. What is the effect where considerable portions of the scene are suddenly thrown into marked shadow, as well as others illuminated with intense light? Is the absolute value of the parts in shadow lowered or raised? Raised, of course, by reflected light. Formerly, to get the contrast between sunlight and shadow in proper scale, the painter would have painted the shadows darker than they were before the sun appeared. Relatively they are darker, since their value, though heightened, is raised infinitely less than the value of the parts in sunlight. Absolutely, their value is raised considerably. If, therefore, they are painted lighter than they were before the sun appeared, they in themselves seem truer. The part of Monet's picture that is in shadow is measurably true, far truer than it would have been if painted under the old theory of correspondence, and had been unnaturally darkened to express the relation of contrast between shadow and sunlight. Scale has been lost. What has been gained? Simply truth of impressionistic effect. Why? Because we know and judge and appreciate and feel the measure of truth with which objects in shadow are represented; we are insensibly more familiar with them in nature than with objects directly sun-illuminated, the value as well as the definition of which are far vaguer to us on account of their blending and infinite heightening by a luminosity absolutely overpowering. In a word, in sunlit landscapes objects in shadow are what customarily and unconsciously we see and note and know, and the illusion is greater if the relation between them and the objects in sunlight, whose value habitually we do not note, be neglected or falsified. Add to this source of illusion the success of Monet in giving a juster value to the sunlit half of his picture than had even been systematically attempted before his time, and his astonishing _trompe-l'oeil_ is, I think, explained. Each part is truer than ever before, and unless one have a specially developed sense of _ensemble_ in this very special matter of values in and affected by sunlight, one gets from Monet an impression of actuality so much greater than he has ever got before, that he may be pardoned for feeling, and even for enthusiastically proclaiming, that in Monet realism finds its apogee. To sum up: The first realists painted _relative_ values; Manet and his derivatives painted _absolute_ values, but in a wisely limited gamut; Monet paints _absolute values in a very wide range, plus sunlight, as nearly as he can get it_--as nearly as pigment can be got to represent it. Perforce he loses scale, and therefore artistic completeness, but he secures an incomparably vivid effect of reality, of nature--and of nature in her gayest, most inspiring manifestation, illuminated directly and