As sculpture is one of the simplest of the arts, painting is one of the most complicated. The harmonies it constructs are composed of almost innumerable elements of lines and forms and colors and degrees of light and dark, and the science it professes is no less than that of the visible aspect of the whole of nature--a science so vast that it never has been and perhaps never can be mastered in its totality. Anything approaching a complete art of painting can exist only in an advanced stage of civilization. An entirely complete art of painting never has existed and probably never will exist. The history of painting, after its early stages, is a history of loss here balancing gain there, of a new means of expression acquired at the cost of an old one. We know comparatively little of the painting of antiquity, but we have no reason to suppose that that art, however admirable, ever attained to ripeness, and we know that the painting of the Orient has stopped short at a comparatively early stage of development. For our purpose the art to be studied is the painting of modern times in Europe from its origin in the Middle Ages. Even in the beginning, or before the beginning, while painting is a decadent reminiscence of the past rather than a prophecy of the new birth, there are decorative splendors in the Byzantine mosaics hardly to be recaptured. Then comes primitive painting, an art of the line and of pure color with little modulation and no attempt at the rendering of solid form. It gradually attains to some sense of relief by the use of degrees of light and less light; but the instant it admits the true shadow, the old brightness and purity of color have become impossible. The line remains dominant for a time, and is carried to the pitch of refinement and beauty, but the love for solid form gradually overcomes it, and in the art of the high Renaissance it takes a second place. Then light and shade begins to be studied for its own sake; color, no longer pure and bright, but deep and resonant, comes in again; the line vanishes altogether, and even form becomes secondary. The last step is taken by Rembrandt, and even color is subordinated to light and shade, which exists alone in a world of brownness. At every step there has been progress, but there has also been regress. Perhaps the greatest balance of gain against loss, and the nearest approach to a complete art of painting, was with the great Venetians. The transformation is still going on, and in our own day we have conquered some corners of the science of visible aspects which were unexplored by our ancestors. But the balance has turned against us; our loss has been greater than our gain; and our art, even in its scientific aspect, is inferior to that of the sixteenth and seventeenth centuries.