The Vision of Leonardo

Leonardo da Vinci was convinced of the power of vision as an instrument of knowledge. He felt that it was above all through our eyes that we grasp and understand the world, that visual representation is the primary method of recording knowledge, and, most importantly, that such knowledge enables us to master and control our environment. The Scholastic tradition of the later Middle Ages gave a privileged status to abstraction, the manipulation of concepts. By giving priority to experience—especially visual experience—and experimentation, Leonardo announced a new era in Western culture. Between the sixteenth century and the nineteenth, the development of science was intimately linked to vision, because the visible could efficiently be recorded. We can estimate a person’s temperature by touching his forehead, but the mercury in the thermometer makes the temperature visible and consequently measurable.

Leonardo, the ultimate “Renaissance man,” is on the one hand a figure of popular legends—the ancestor of air travel who dreamed up flying machines, and the painter of the Mona Lisa, an image familiar to millions of people who have no idea when the Renaissance was or, for that matter, why the picture is so special. The crude, sometimes even diagrammatic reproductions found everywhere convey almost nothing of the spatial complexity and the atmosphere that made the art of Leonardo revolutionary. On the other hand, historians see him as a pivotal artist and a true pioneer of modern science, whose paintings, drawings, and notes pose complex intellectual problems that still defy explanation.

This summer the Museum of Science in Boston presented an exhibition designed to reconcile the popular and the learned view by giving greater precision and depth to the various aspects of Leonardo’s genius. The show, entitled “Leonardo da Vinci: Scientist, Inventor, Artist,” grew more complex during its itinerary, which began in Malmö, Sweden, where it was specifically concerned with Leonardo’s studies of bridges. After several stops in Germany and Austria, the show’s most elaborate version went on view in Boston, and it will soon open in Singapore. Sponsored by Mercedes-Benz and a Swiss watch company, it has been accompanied by a catalog prepared for the German version which only partially corresponds to what we saw in Boston; it has, however, catalog entries for most of the works of art exhibited.

In Boston the exhibition began with a general introduction to Leonardo’s life on video; it then led to rooms that displayed a few objects, such as early printed books and room furnishings, intended to evoke a Renaissance setting, as well as facsimile reproductions of Leonardo’s drawings and manuscripts, and models made from his designs. These exhibits were interspersed with consoles where the visi-tor could use interactive audio-visual equipment to explore various aspects of Leonardo’s work. A special room was devoted to actual works of art—the most questionable part of the exhibition.

Most spectacularly, perhaps, in the main space of the museum we could see a birdlike flying machine, built according to Leonardo’s specifications, next to a recent man-powered flying contraption that actually works. Named Daedalus, the latter machine is a propeller airplane designed by an MIT team; it does not flap its wings in birdlike fashion as Leonardo’s does. This amazing apparatus, made mostly of new, light materials like mylar film and graphite epoxy tubing unknown in Leonardo’s time, weighs only seventy pounds, yet has a wing span of 112 feet.

Leonardo had already figured out that while birds had mostly breast muscles, man’s physical power was concentrated in his legs, and he had the wings of his machine moved by pedals. Daedalus’s modern propeller, whose function Leonardo did not conceive, is also powered by pedaling. On April 22, 1988, another model of Daedalus, manned by a Greek athlete called Kanellos Kanellopoulos, flew the seventy-two miles from Crete to Greece in three hours and fifty-five minutes. The pilot crashed, apparently from exhaustion, just ten yards offshore. The fall was fatal only for the machine. The one permanently exhibited in the Boston Museum of Science, which was used for test flights in constructing Daedalus, is almost identical to it, and bears witness to the haunting power of classical myth and Leonardo’s dreams.

The Boston exhibition had three parts: the first was concerned with Leonardo as an artist, the second with his investigations as an engineer or inventor, and the last with Leonardo as a scientist. His life has traditionally been seen as following roughly the same sequence. Born outside Florence in 1452, Leonardo was trained in the studio of the Florentine painter and sculptor Verrocchio and he practiced painting in Florence until 1481. When he applied for a job with the ruler of Milan, Ludovico il Moro, he presented himself as being as much an engineer as an artist. In his later years—when he restlessly moved between Milan, Florence, Rome, and finally the court of Francis I in France—he became increasingly absorbed by his scientific investigations.

In describing Leonardo’s training, the exhibition did not just show with images and texts how knowledge was passed on in a Renaissance artist’s studio; it tried to involve the public actively. The visitor could use an apparatus similar to the one illustrated in a famous Dürer woodcut, which makes it possible to trace with a marker what one sees through a glass pane on the pane itself. The experiment was designed to enable the viewer to grasp how in perspective objects look smaller with distance.

The introduction of single point (or “scientific”) perspective was indeed one of the major developments of the Renaissance and still something of a novelty in Leonardo’s youth. For most artists, perspective was defined by a set of rules and procedures. But Leonardo insisted on understanding it as fully as possible, particularly the relation between the linear perspective used by artists to suggest three-dimensional space—what he called “artificial perspective”—and the physiology of visual perception, or “natural perspective.” He investigated, for example, the “distortions” in an image caused by the artist’s working on a flat surface, while the retina, on which the image forms in the eye, is curved. As usual, Leonardo never systematized his observations and ideas on the subject, and ascertaining his conclusions from his many notes and diagrams is one of the more challenging problems in the highly complex and specialized history of perspective.

In the studio of Verrocchio, Leonardo and his fellow apprentices made beautiful studies of draperies; we know that to do so they covered some kind of clay dummy or mannequin with cloth that was then kept in place by being dipped in plaster. Such exercises in drawing attempted to give the impression of volume by the distribution of light and dark through shading. Visitors to the exhibition were invited to try such a drawing themselves, and they were provided with paper on which the outlines of models on view were already drawn so that they could just fill in the shading that gives three-dimensionality; they could also achieve different effects by changing the lighting on the model.

Throughout the Boston exhibition, the organizers tried by such means to relate complex artistic and scientific issues to simple physical experience. In the section on Leonardo’s study of anatomy, beside Leonardo’s stunning anatomical drawings (which were the subject of an exhibition in London not long ago), a modern anatomical model could be taken apart and reassembled so that the visitor could see for himself how the heart, liver, kidneys, lungs, and other organs fit together in the human frame. At a nearby exhibit the visitor could handle an actual chicken foot and see how it works by pulling the tendons to make the claws move (an experience fewer and fewer children have had today when chickens appear feetless in most kitchens). It was this hands-on approach that made the Boston exhibition original and distinguished it from the Leonardo exhibition at the IBM gallery in New York in 1983 or the more scholarly one at the Musée des Beaux Arts de Montréal in 1987. The Boston show was true to the spirit of Leonardo insofar as he insisted that experience took precedence over authority in the acquisition of knowledge and understanding.

The claim, implicit in the exhibition, that Leonardo moved away from art to science, masterfully argued by Freud in his famous essay of 1910, is only partly convincing. Certainly, his intellectual range and ambition vastly expanded as he grew older. But Leonardo seems always to have been unwilling to finish paintings. As Sydney Freedberg put it in his memorable analysis of the early and unfinished Adoration of the Magi:

So much thought went into the conception of the Adoration that it is not surprising that there was not energy, or no interest, left for the labor of its execution. The physical completion of the painting must have seemed to Leonardo a problem of much lesser order than its ideation.¹

This failure to finish work would recur again and again. Leonardo left very few completed paintings (even when we consider that some have been lost) and an exceptionally large number of projects in various unfinished states, ranging from quickly made drawings to detailed cartoons, and including a full-size clay model of the horse for a gigantic equestrian monument which, however, never had a rider. It was used for target practice by the French soldiers occupying Milan and finally crumbled away.

Leonardo’s impatience with the practical difficulties of completing a work and his excessively high standards help to explain why he abandoned many paintings. But in spite of his growing concerns with scientific problems of many different kinds, he never ceased to paint, except, it seems, when his hand became paralyzed; and he always thought of himself as an artist. For him painting was “the sole means of reproducing all the known works of nature.” To quote Freedberg: “Since, in Leonardo’s view, knowledge was indivisible and painting the preferred instrument of its communication, his principles of science were principles of painting too.”²

To paint in the intellectually ambitious ways to which Leonardo aspired even as a very young man, the artist could not be content with observing and recording the appearance of nature; he had to understand how it “works.” As he put it:

This is the true rule how observers of natural effects must proceed: while nature begins with reasons and ends in experience, we must follow the reverse [path], beginning with experience and with that investigating the reasons.³

Leonardo firmly believed that by understanding how nature works, man could then work as nature did; to imitate nature was not simply to hold up a mirror to it, but to construct on the same principles a new world in which one could act on superior knowledge.

Visual representation was the main vehicle he chose to express his thought, because sight was his means of investigation; his abundant writings are in most cases appended to sketches, diagrams, and other visual notations. It is therefore impossible to understand him as an inventor or a scientist without some sense of his powers as an artist. Here the exhibition fell short. While it succeeded in demonstrating the elementary aspects of artistic practice, such as perspective and modeling, it gave little sense of the extreme sophistication of Leonardo’s representational skills and how they affected the pictorial tradition.

The room called the Art Gallery was filled with a baffling collection of disparate objects. The explanatory texts posted alongside them did not seem to have been devised with the same careful attention as those accompanying the technical and scientific displays. As well as exhibiting copies of Leonardo’s work and paintings showing his influence on his contemporaries, the organizers understandably wanted to present one or two originals by Leonardo; but instead of showing work that has been established as being by him, they showed, under the questionable title of The Angel in the Flesh, a bizarre drawing for a lost painting, The Angel of the Annunciation. Several authentic autograph drawings exist for this work, as well as a painting by a follower. It is a striking conception which presents Gabriel facing the viewer who is thereby put, so to speak, in the shoes of the Virgin Mary.

In the drawing exhibited, however, Gabriel has been turned into some kind of hermaphrodite freak by the addition of an erect penis and a female breast. Is it possible that such a weird image is by Leonardo? Even if we assume that the drawing is authentic, we still want to know whether it has been tampered with by a later hand. Whatever the status of this drawing, it does not give a fair idea of Leonardo as a draftsman.

Some parts of the exhibition were positively misleading. For instance, the organizers showed what they called “an impeccable copy” of the Mona Lisa, said to be the one that replaced the original in the Louvre after it was stolen for a brief period in 1911. It looked to me like a carefully but harshly painted piece of work. A good photographic reproduction would have done more justice to the charm, complexity, and subtlety of Leonardo’s picture, in which there are no hard edges and where the very atmosphere seems in motion.

The works presented are by no means all inferior or irrelevant. The copy of the Madonna of the Rocks is a very interesting variant of the masterpiece in the Louvre, and it may well have been produced within Leonardo’s immediate circle. Far better than the indifferent copy of Mona Lisa, it gives an idea of the famous sfumato of Leonardo’s mature paintings, the way that he envelops everything in a thick atmosphere evoked by a handling of light that binds all objects together. I was also happy to see a version by another artist of the so-called Monna Vanna or Nude Mona Lisa, a lost work of Leonardo’s. It is thought that Leonardo planned a nude portrait of the mistress of his patron Giuliano dei Medici, although he probably never finished it. David Brown, of the National Gallery in Washington, has plausibly suggested that Leonardo’s justification for taking on such a bold project was that he wanted to recreate a lost masterpiece of classical antiquity, the portrait of Campaspe, the mistress of Alexander the Great, by the painter Apelles.⁴ Whatever Leonardo’s original intentions may have been, the result was a great success, and it set off a fashion for such nude portraits throughout Europe during the entire sixteenth century. Along with a cartoon preserved in the museum at Chantilly, the version exhibited in Boston, whether or not it was painted by Leonardo’s pupil and friend Salai, as the catalog claims, seems to come closest to Leonardo’s initial conception.

More than Leonardo’s immediate associates, Correggio, forty-two years younger than Leonardo, was his true heir as a painter. He had the perseverance as well as the genius needed to make a fictitious world of dreams seem real, a task that Leonardo was generally too impatient to carry out. Correggio’s painting of Io, in Vienna, in which Jupiter in the form of a cloud is embracing a nymph, is one of the most breathtaking demonstrations of what painting can do. It makes you feel that you actually see the impossible happen in front of you. The mediocre and rather ugly copy of Correggio’s Madonna del Latte shown in the exhibition (the original is in the Budapest Museum), whether or not it was painted in the early sixteenth century as claimed, hardly gave a visitor any sense of how Correggio was inspired by Leonardo.

Equally puzzling is the replica of Bernardo Luini’s Holy Family from the Ambrosiana Gallery in Milan, which is itself based on Leonardo’s cartoon of The Virgin and Child with St. Anne and John the Baptist (London, Royal Academy), although with Saint Joseph added to the right. Subtitled The Russian Madonna (for reasons that are not clear), this canvas of rather high quality was exhibited as the work of an “anonymous follower of Leonardo da Vinci after 1530.” Why precisely “after 1530” I do not know, but Carlo Pedretti, one of the three members of the exhibition committee, has suggested elsewhere that it might be by Angelika Kauffmann, who was born in 1741.

That Raphael learned much from his older contemporary is well known and can easily be seen, for example, from any good modern reproduction of his Transfiguration in the Vatican. The organizers of the exhibition chose instead three allegedly original paintings by Raphael. One, from a private collection, is a Betrothal of St. Catherine, which Carlo Pedretti, in his book on Raphael, attributed to the artist’s early years, although with little agreement from other scholars. The catalog entry by Nathalie Guttmann accepts the attribution to Raphael but does not mention Leonardo and indeed, although the infant Christ might be considered vaguely Leonardesque, this work could hardly be considered a good example of Leonardo’s influence. The panel might be of interest in an art museum, but it is pointless to include it in an exhibition on Leonardo such as the one at the Museum of Science.

Raphael’s Leonardism is also suggested in two versions of the Young Saint John the Baptist, one belonging to the Galerie Hans in Hamburg, the other from a private Swiss collection. Both panels employ a composition designed by Raphael during the last phase of his career, when he was exploring the implications of Leonardo’s dramatic chiaroscuro. Although no version of the composition is entirely convincing as the work of Raphael himself, the one in the Uffizi in Florence can be traced to the Medici collections back to 1589 and has some claims to having been produced in Raphael’s studio. Of the two versions exhibited in Boston, the one presented as the work of “Raphael and his studio” would be better described as a painstaking, somewhat stiffly painted copy. Although perhaps more superficially attractive, the one attributed to Raphael alone seems to me inferior; those who claim that it is the work of Raphael’s hand betray in this case a low estimate of his genius.

Leonardo was trained in the studio of a sculptor; he worked for many years on projects for equestrian monuments, including the colossal clay horse in Milan. Yet no existing sculpture can be attributed to him with any certainty. Early in this century a great stir was created when the Berlin Museum acquired a bust of Flora attributed to Leonardo under the aegis of the famous Wilhelm Bode, a specialist in Italian Renaissance sculpture. The bust was then denounced as a fake. Since that time scholars have generally been cautious about ascribing sculpture to Leonardo. The Boston exhibition presented two candidates. One was a terra cotta bust of the young Christ (Saint John the Baptist has also been suggested). It is a handsome object whose authenticity as a Renaissance work has been confirmed by scientific examination. Leonardo scholars are divided over it. Martin Kemp has written that in the absence of any sculpture clearly by Leonardo it is impossible to come to a firm conclusion about this piece; still he makes a clear and precise case for the possibility that Leonardo executed it in the late 1490s when he was working on The Last Supper in the refectory of Santa Maria delle Grazie in Milan. Yet the sculpture also closely reflects the methods of Verrocchio, and other scholars, although prepared to see it as the work of Leonardo, would place it earlier in his career. Some scholars, however, are not at all convinced by this attribution.

The display of the bust was an auspicious way of introducing the vexing issue of Leonardo as a sculptor. But it was unfortunately placed in the exhibition next to a bizarre object, a wax statuette of a rider on a bucking horse never before seen in public. In the explanatory label, the statuette was said to have belonged to Francesco Melzi, a student and companion of Leonardo, a provenance unfortunately based on hearsay. It looks suspiciously like the kind of Renaissance fantasy that nineteenth-century sculptors like Barye occasionally produced. Although I have not had a chance to examine it closely, I would be surprised if this wax figurine were readily accepted as Leonardo’s. But above all, I fail to see the point of presenting to the uninformed visitor highly debatable hypotheses as if they were confirmed.

By contrast, the damaged but beautiful and moving Pietà, a painting characteristic of the idiosyncratic late manner of Bramantino, a Milanese contemporary of Leonardo, is accompanied by an excellent catalog entry by Pietro Marani, a learned and sensitive scholar of Lombard painting. He argues persuasively for seeing the influence of Leonardo on the painting’s moodily expressive style. The visitor to the exhibition, however, can only be confused by seeing that the name of Bramantino is also attached to a clumsy adaptation of Leonardo’s Madonna of the Rocks. The garbled but reverent catalog entry by Gabriella Ferri Piccaluga does not help to justify the presence of a picture whose only point here would be to show how little an insipid painter of the time understood of what Leonardo was about.

The disparate objects assembled in this “Art Gallery” have one thing in common: with very few exceptions they all belong to private collectors or to art dealers. In view of the inflated claims made for them, one begins to wonder about the motives for showing them. My worry, however, is not so much the ethical legitimacy of such a display as the kind of confusion it can cause for the public. The rest of the exhibition is clearly and justifiably intended to educate the visitor; this section makes no attempt to present any clear argument about Leonardo. Some of the exhibits have practically no relation to him, and the captions leave one with the impression that art historical judgments are purely arbitrary. Excellent works are given the same attention as very poor ones, and the visitor comes away with no sense whatever of what distinguishes high skill from the work of a hack, and with little comprehension of Leonardo’s supreme accomplishment as an artist, and of how it was understood and misunderstood by his contemporaries and his successors.

3.

Should the Museum of Science, concerned as it is with scientific matters, have stayed away from problems of art history and connoisseurship, even by implication? To leave out Leonardo the artist entirely would obviously have been wrong: his various activities can be understood coherently only through his concern with representation. And it is precisely the unique configuration of all the different consequences and ramifications of his imagination that make Leonardo such a fascinating, even uncanny person; his very peculiarity is a mystery that haunts our culture.

His first biographer, Giorgio Vasari, in the Lives already stressed the singularity of Leonardo’s character—the innumerable projects he never finished, for example (comincio molte cose, e nessunamai fini), and his habit of purchasing caged birds to set them free. He also suggests that Leonardo, himself exceptionally good-looking, was drawn to beautiful boys. The study of the artist’s life took a new turn in 1910 when Freud published his short book entitled Eine Kindheitserinnerung des Leonardo da Vincis (“A Childhood Memory of Leonardo da Vinci”). This was an attempt to account for Leonardo’s peculiarities through the circumstances of his early childhood. Leonardo was the illegitimate son of a notary, Ser Piero, and a woman of humble family called Catarina. Ser Piero married another woman, but the union was childless and he eventually took the boy into his household. Freud assumed that Leonardo spent his first five years in an intense relationship with his mother, and then found a second loving mother figure in his stepmother. He speculated that Leonardo’s homosexual tendencies were based on repression of incestuous desire.

The aims of Freud in this little book were complex. His main concern was to discuss childhood sexuality and the psychogenesis of homosexuality in connection with Leonardo, but his ambition went further. Although in some passages he disclaimed any intention of explaining the art of Leonardo, others showed his conviction that he had figured out the reason for the fascination of the Mona Lisa’s celebrated smile: it evokes, he thought, echoes of our own emotional relations with our mothers. He also insisted that Leonardo’s peculiar psychological history accounted for the fact that in his Saint Anne and the Virgin both women are roughly the same age, reflecting the presence of two young, loving mother figures in Leonardo’s experience, Catarina and Ser Piero’s wife, Donna Albiera. This short monograph engendered the controversial historical genre known as psychobiography.

Freud’s tract had only a limited impact on Leonardo studies until Meyer Schapiro published two articles in 1956 in which he discussed Freud’s thesis, pointing out both some mistakes in his documentation and the difficulties posed by new evidence that had emerged since Freud’s original publication. The early recollection Freud cited comes from a passage in Leonardo’s notebooks for which Freud unfortunately used an inaccurate translation:

It seems that I was always destined to be so deeply concerned with vultures; for I recall as one of my earliest memories that while I was in my cradle a vulture came down to me, and opened my mouth with its tail, and struck me many times with its tail against my lips.

Freud speculated that this early recollection reflected Leonardo’s fantasies about his mother. The image of the beating bird’s tail could be interpreted not only as a representation of the infant’s pleasurable suckling on the breast but also as a phallic symbol based on the male child’s speculations about his mother’s missing penis. To support his hypothesis, Freud wrote at length on the vulture as a mother symbol in Egyptian mythology. The relevance of such symbolism to Leonardo would be tenuous in any case. But since Leonardo’s original text mentions not a vulture but, as Schapiro pointed out, a kite, the entire argument collapses.

Schapiro made a good case that the early memory recorded by Leonardo in later life is not a spontaneous fantasy (let alone an actual recollection) but a deliberate rhetorical device borrowed from ancient authors to express premonitions of greatness, a fancy literary way of saying, “It was my destiny to study the flight of birds,” the kite having been traditionally characterized as the bird with the flight that comes nearest to perfection. Schapiro also found examples of pictures painted before Leonardo in which Saint Anne and the Virgin were represented as of the same age, which at least weakens the claim that this iconographic peculiarity has personal psychological significance.⁵

Schapiro’s article also showed to what extent Freud’s understanding of Leonardo’s life and character depended on the then-famous book The Romance of Leonardo da Vinci by Dmitri Merejkowski, a romantic historical novel based on the artist’s life. The image Freud draws of the intense emotional relation between Catarina and her child is directly drawn from the novel and is entirely imaginary. This implicitly poses the question whether there is any essential difference between Freud’s reconstruction and the intuitive insights of the novelist, which may have value but on which one would not confer scientific authority of the kind claimed by psychoanalysis.

More than any other method of psychological assessment, psychoanalysis (a therapeutic method) depends on the patient’s active engagement (usually through free association) in uncovering the deep motivations of symptoms. If Leonardo’s “early recollection” of a bird is a rhetorical device, this does not preclude its having deeper psychological motivations; but what specifically these motivations were could only have been determined with the cooperation of Leonardo himself. Using psychoanalytic theory today, one can only form a plausible hypothesis from a coherent but altogether hypothetical narrative of his life and character. I see no fundamental distinction between this and Merejkowski’s conscientiously documented “romance.”

There is no agreement, for instance, even about Leonardo’s sexuality, a topic that was raised discreetly by the Boston exhibition but is inescapable because, as Kenneth Clark put it, “it colors his outlook in a way that the same characteristic in other great men does not always do.” Whether he was an active homosexual or completely inhibited, as claimed by Freud, perhaps more on the basis of Victorian prudishness than psychoanalytic evidence, is uncertain. But as Kenneth Clark put it in his benign, old-fashioned way:

We cannot look at Leonardo’s work and seriously maintain that he had the normal man’s feelings for women. And those who wish, in the interests of morality, to reduce Leonardo, that inexhaustible source of creative power, to a neutral or sexless agency, have a strange idea of doing service to his reputation.

In fact, when we take account of recent studies of Florentine sexual practices, it seems unlikely that Leonardo had no sex life. But there is no question also that his sexual activities, whatever they were, had to be kept hidden, and this must have helped to create the atmosphere of mysteriousness that surrounded Leonardo, an atmosphere he himself encouraged.

His well-known habit of writing from right to left in mirror image, for example, surely had more to do with the fact that he was left-handed than with secrecy; it is not that difficult to read such writing, either with or without a mirror, and it cannot be considered the equivalent, for example, of Samuel Pepys’s coded script, which was meant to protect indiscreet diary entries from being revealed. On the other hand, most left-handed people learn to write from left to right, and I suspect Leonardo chose to write the way he did not only because it may have been easier, but also to puzzle or amaze.

His attitude to antiquity is sometimes misconstrued. Because he questioned authority and wanted to rely on experience and observation, it is often assumed that he attached little value to classical culture. But this is clearly untrue. Even his investigations of the flight of birds and the possibility of building a flying machine are quite obviously inspired by the ancient myth of Daedalus. Not only does close investigation of his notes reveal many references to ancient texts, but his art was also clearly enriched by his knowledge of the remains of antiquity. The riders in the background of the early Adoration of the Magi show this clearly enough. At the same time, there is a dreamlike atmosphere in his evocation of the ancient world that is in no way archeological or pedantic.

Leonardo was a keen observer of natural phenomena, but he also had a rich and vivid fantasy life, which he cultivated. A famous passage of the notebooks points out how we can read images into accidental stains on walls. These two aspects of his mind may seem quite different, but they are brought together by the power of imagination which was developed in him to an extreme degree and to which he attached particular importance. He saw a close relation between visual perception, imagination, and dreams. In one of the isolated thoughts he entered in his notebooks, he wrote: “Why does the eye see a thing more clearly [più certa] in dreams than with the imagination when awake?” (I follow J.P. Richter’s translation but più certa could also be rendered as “more real” or “more vivid.”) It is clear that if visual perception—the eye—was the foundation of knowledge, perception by itself was not the whole of vision. Imagination, the power of the mind to produce images, to give visual form to its conceptions, was also crucial. This power was applied to both the perception of the physical world and to the fantasies of the mind to which it gave equally vivid and convincing form. It was this visualizing power of the mind and its representation in drawing and painting that gave unity to knowledge. For Leonardo, fantastic dreamer and scientist, there was no art without science or science without art. Two quotations make this clear:

There is no part of astronomy that does not make use of visual lines and of perspective—the child of painting—for it is the painter who created perspective to meet the requirements of his art….

The painter who draws merely by practice and by eye, without any reason, is like a mirror which copies everything placed in front of it without knowing about them.⁶

Beyond science, however, Leonardo wanted to give to the representation of the world, whether real or not, the vividness of a dream. This is what gives his art, whether a drawing of leaves of grass or the eddies of a river, or The Virgin with Saint Anne, its unmatched poetic quality.