Leonardo da Vinci was a genius at painting, no doubt about it. He invented sfumato, inaugurated the High Renaissance, and created what is arguably the cleverest composition in the history of art, The Last Supper.
Was he also a genius at science? The casual visitor to the current exhibition of the Codex Leicester at the American Museum of Natural History in New York (through Jan. 1, 1997) might come away with the vague impression that he was. The curators describe the 72-page manuscript, on loan to the museum from Bill Gates (who bought it two years ago for $30.8 million), as "a masterpiece of science." One of the catalog essayists writes that "[a]s a scientist, Leonardo rates more space in the reputable Dictionary of Scientific Biography than Kepler, Galileo, and Einstein combined."
But Leonardo was not a genius the way Einstein or Galileo was. He was more a genius the way Buckminster Fuller was, if that is a way of being a genius.
For a couple of centuries after his death in 1519, Leonardo was seen mainly as a painter, albeit a preternaturally gifted one. His artistic legacy comprises the Mona Lisa and 14 other paintings (several of them unfinished), together with a treatise on painting. But he had also left behind some 7,000 pages of unpublished notes on hydraulics, geology, anatomy, flight, ballistics, botany, optics, and astronomy, as well as designs for all sorts of fantastical inventions. It was not until the time of the Industrial Revolution that his notebooks, by then scattered all over Europe, were paid serious attention. Soon, he was being celebrated for his "precursive" genius. He had beaten Newton to the theory of gravity and Copernicus to heliocentrism. He had worked out the circulation of the blood before William Harvey. He had grasped the principle of erosion more completely than Georges Cuvier. He had invented the airplane, the tank, the bicycle, the modern toilet--such are the claims that have been made for him.
What is the evidence for such deep originality in the CodexLeicester? The manuscript itself, whose pages are dimly illumined in a series of glass cases at the museum, is not, at first blush, a fetching object. You can't exactly read the thing, since Leonardo's jottings are in medieval Italian, and are rendered in his famous mirror-image script. The hundreds of marginal drawings have some aesthetic interest--especially those depicting the flow of water--but they are mainly simple geometrical diagrams and doodles. The earls of Leicester, who owned the codex since 1717, seem rarely to have looked at it. "Nothing like three centuries of aristocratic incuriousity to keep ink and paper in near-perfect condition," commented one wag. (Between the Leicesters and Bill Gates, the notebook was owned for a dozen or so years by Armand Hammer--who, with his unerring flair for the ludicrous, insisted it be called the Codex Hammer and claimed that he had retained a squad of elite commandos trained in kung fu and armed with Uzis to guard it round the clock.)
Looking at the English translation of the codex on a CD-ROM at the exhibit, I saw that what began as an attempt by Leonardo to set down the first principles of the behavior of water ended up as a farrago of observations and musings--fanciful, insightful, analytically maddening. At one point, for example, he notes that the higher a column of water, the greater the pressure it exerts--a valid, if unexciting, conclusion. But elsewhere in the codex, he maintains that only moving water produces pressure at the bottom, reasoning that the still water of a pond, after all, does not press down the grasses that grow on the bottom. Not only is this breathtakingly wrongheaded, it contradicts the previous principle.
Leonardo's greatest shortcoming as a scientific thinker was, not paradoxically, his greatest strength as an artist: his eye. This, for him, was the ultimate epistemic instrument, one to be trusted over all classical authorities. "Do you not see that the eye embraces the beauty of the whole world?" he wrote, insisting that the visual eye was, pre-eminently, the real. It is Leonardo's sheer ability to see--to notice, in a way that no one had before, precisely what it looks like when two streams of water merge--that accounts for the thrilling bits of the CodexLeicester.
The problem was that Leonardo knew very little mathematics. Algebra was a closed book to him, and he was poor at figures. (When he writes, "Let no one read me who is not a mathematician," he is using the term loosely, to suggest a rigorous cast of mind.) His ocular observations were in a qualitative vein, hearkening back to Aristotelian science rather than forward to Newton. That is fine when it comes, say, to anatomy--in which Leonardo was also well-served by his willingness to thrust his nicely manicured hands into the guts of dead felons he was dissecting. But it's disastrous in dynamics, where his experiments led him to conclude that both the velocity of a falling object and the distance fallen are proportional to the time of the fall--which a moment's reflection exposes as a logical absurdity. (The only other figure I can think of who had similar claims to genius both in art and science, Goethe, was also a mathematical innocent. But where Leonardo had a keen respect for mathematics, Goethe was openly contemptuous of it.) The true precursor of the scientific revolution was Galileo, who proclaimed, with almost mystical conviction, that the Book of Nature was written in the language of mathematics.
As for Leonardo's "inventions," those that were sound from an engineering point of view were usually borrowed from contemporaries. His elaborate hoists and cranes were designed by Brunelleschi, his engines of war by the German engineer Konrad Keyser, his "automobile" by the Sienese Francesco di Giorgio Martini. (On the other hand, a device described in the Codex Leicester that, the exhibition catalogue notes, "sounds curiously similar to a modern espresso machine," seems entirely original.) Leonardo's "flying machine" would not have flown, but that hardly counts against its visual bravura; one version resembled a calabash shell crossed with a windmill, and another, a four-winged butterfly. Leonardo was a man who, according to one biographer, "was plunged into a kind of ecstasy by devising never-ending systems of cogwheels and screws"--rather like Buckminster Fuller deliriously multiplying geodesics.
If there was a bit of Fuller in Leonardo, there was also a bit of Liberace in this theatrical, high-living dandy who favored brocade doublets and bad boys with pretty faces. (Since his disciples were chosen for their looks, he had no distinguished successors.) Little of Leonardo's weirdness is conveyed by the CodexLeicester exhibit--though Isabella Rosellini's blue-velveteen voice narrating the exhibit's eight-minute biographical video helps somewhat. Here was a Renaissance humanist who regarded his fellow men as "stupid and deranged," "sacks for food," and "fillers-up of privies," and relished the thought of humanity's destruction in a universal deluge. Leonardo's obsession with swirling water--which found scientific expression in the CodexLeicester and sublime artistic expression in the drawings he did toward the end of his life--could be pretty morbid.