Leonardo’s discoveries, pursued with the most patient and gradual care, shocked no one and were quickly taken up. He was nearly thirty before he reached consciousness of his mission, and having attained his artistic end, he dropped painting, with a kind of scorn, for mathematical and scientific investigation. In his admirable “Tractate on Painting” he has left the fullest and most eloquent records of his ideals. The first is that the painter must know clearly what he is about. “Without good theory no good practice is possible.” Next the artist should be in a filial relation to nature, admiring and imitating her directly, and not through the eyes of other artists. As to the main object of painting, Leonardo wavers between two definitions. Repeatedly he insists that that painting is greatest which through the postures of the body shows the emotions of the soul. As often, he uses a more technical definition—the chief business of painting is to create a sense of relief or projection where there is none. This relief is effected by delicate and accurate distribution of light and shade. Light and dark are conceived in a double fashion, as factors in relief and as offering intrinsic beauties in their gradations. We have a refinement on the method of Masaccio, which is merely structural and dramatic and without much intrinsic charm. But the new beauty of chiaroscuro soon turns out to be incompatible with the old beauty of frank color. Pictures become dusky and mysterious, tending to black and white values. Ever since Leonardo, academic painting has had the sore limitation of regarding shadow as negation of color. It is the defect of his teaching and practice. On broader matters, however, Leonardo is profoundly right. Seeing is a mental process and should be selective. Represent all the muscles emphatically, and your nude will look like a sack full of nuts. Accuracy is necessary, but is of no value without accompanying dignity and grace. Choose the most gracious aspects of reality, the pervasive moderate light of evening rather than the sharp glare of the overhead sun. Observe deaf-mutes so that you may learn the possibilities of expression through gestures. Seek equilibrium and an active and vital balance whether in the pose of the single figure or in the relations of the figures to each other. Get the action right, and afterwards add the details. These are some of the precepts which Leonardo scribbled off about the year 1500 when he was nearing fifty and his work as a painter was almost over. He is really describing the principles under which, while accepting the richness and variety of the early Renaissance style, he had once for all put it in order.