The likeness of the mind of God

Since classical times painting had been classed among the mechanical arts, and Leonardo, like Sir Joshua Reynolds in his Discourses, is concerned to establish its respectability by proving that it is a mental activity and a science. The destruction of such an artificial premise naturally involves him in some artificiality himself, but above these sophistries, which are harmless enough if judged by the standards of contemporary literature, there towers a noble and thrilling conception of what painting should be. In the first place, it is a recreation of the visible world. Leonardo always insists on this godlike quality of the painter's imagination. From the divine element in the science of painting it follows that the mind of the painter is transformed into the likeness of the mind of God. It is this view of art as creation which makes him insist that the painter must be universal, must neglect no aspect of nature; and for the same reason he must be a scientist, that is to say, must understand the inner nature of what he paints almost as if he had created it himself. "If you despise painting," he says, "which is the sole means of reproducing all the known works of nature, you despise an invention which with subtle and philosophic speculation considers all the qualities of forms: seas, plants, animals, grasses, flowers, all of which are encircled in light and shadow." But the painter must not only recreate the semblance of things seen: he must select and dispose them with harmonious intention. Painting, he says, depends on "l'armonica proporzionalita delle parti che compongono il tutto, che contenta il senso". Here, as nowhere else, Leonardo shows himself touched by the predominant Platonism of his time, for the idea that the visual arts were a sort of frozen music was familiar to many theorists of the Renaissance, and had been given superb expression by Leon Battista Alberti. But in his enthusiasm for painting, Leonardo goes farther and claims that painting is superior to music in so far as it is frozen, since its sequences are not fleeting sounds or images, si veloce nel nascere come nel morire, but can be apprehended immediately and contemplated indefinitely.

This exposition of the relative immediacy and permanence of the sensations aroused by the arts, anticipating to some extent the theories of Lessing, is, from a critical point of view, the most valuable part of the Trattato. But strict logic was no part of Leonardo's equipment, and when he comes to compare painting to sculpture his personal prejudices rush in, to the confusion of his aesthetic theories, but to the vast enrichment of our knowledge of his character.

For that side of painting which consists in the harmonious composition of proportionate parts Leonardo gives no rules, though in one abstruse passage he hints at a means of establishing an equivalent to certain musical intervals. The academic advice and instruction which fill a great part of the Trattato are concerned with painting as the science by which visible objects are recreated in permanent shape. And since the exact sciences must be stated in mathematical terms, Leonardo insists that the student of painting must be grounded in mathematics. This union of art and mathematics is far from our own way of thinking, but it was fundamental to the Renaissance. It was the basis of perspective, that article of faith of the fifteenth-century painters, through which they hoped to surpass even the painters of antiquity. By perspective they sometimes meant the whole science of vision, the means by which a visual impression is received in the retina; more frequently they limited the word to the scientific representation of receding figures in space. But even in this narrower interpretation, the study of perspective involved a real mastery of mathematics: and this the great artists of the quattrocento--Brunelleschi, Masaccio, Uccello, Mantegna, Bramante, above all Piero della Francesca--had evidently possessed. All this must be borne in mind when studying the diagrams and calculations which fill the pages of Leonardo's writings on art; and anyone who has not read earlier writings on perspective cannot pretend to say how far he made any original contribution to the subject. Apparently his exposition of linear perspective is chiefly derivative. His notes on the perspective of colour and what he calls the perspective of disappearance, however, contain many of those acute observations in which he anticipated the doctrines of impressionism; but he was so far from carrying out these delicate observations of colour and atmosphere in his painting that they were entirely without influence. The reverse is true of his observations on light and shade. Like all good Florentines he felt the importance of relief, but he was not content to achieve it by the subtle combination of drawing and surface modelling which the painters of the quattrocento had brought to perfection. He wished to achieve relief through the scientific use of light and shade. In the Trattato he says--under the heading "which is the more difficult, light and shade or good drawing"--"Shadows have their boundaries at certain determinable points. He who is ignorant of these will produce work without relief; and relief is the summit and the soul of painting." It was in order to establish scientifically the determinable boundaries of shadows on curved surfaces that he drew the long series of diagrams showing the effect of light falling on spheres and cylinders, crossing, reflecting, intersecting with endless variety, which we find in MS. C of about 1490. The calculations are so complex and abstruse that we feel in them, almost for the first time, Leonardo's tendency to pursue research for its own sake, rather than as an aid to his art. How far, in fact, his art was affected we cannot determine. The drawings which show his greatest mastery of chiaroscuro from a naturalistic point of view belong to the years just before this period. He never surpassed the rendering of light passing over curved surfaces in the studies of skulls dated 1489. But it is characteristic of his development that he should grow dissatisfied with this empirical mastery and wish to reduce it to rule. Critics have complained that the scientific study of light and shade led to a kind of academism in Leonardo's later work, and was ultimately responsible for the artificiality of the Louvre St John. This is certainly untrue. Much of Leonardo's most sensitive and unacademic use of chiaroscuro dates from long after his investigations into its nature. And to those who maintain that the innumerable patient diagrams of criss-cross rays were a tragic waste of time, Leonardo might well have replied that between the Ginevra Benci and the Mona Lisa there is a difference in fullness and continuity of modelling which he, at any rate, could only have achieved by the scientific study of light striking a sphere. The effect of Leonardo's passion for chiaroscuro, both in his own art and in that of his followers, I shall discuss later on. But while dealing with the Trattato I must quote one passage which has a bearing on his whole feeling for the subject. "Very great charm of shadow and light", he says, "is to be found in the faces of those who sit in the doors of dark houses. The eye of the spectator sees that part of the face which is in shadow lost in the darkness of the house, and that part of the face which is lit draws its brilliancy from the splendour of the sky. From this intensification of light and shade the face gains greatly in relief . . . and in beauty." Here is the description of a seicento picture, a Caravaggio or a Rembrandt, as far as possible from the theory and practice of Leonardo's day, or, as we shall see, his own academic theory.