Patrons might find his failures to complete a commission exasperating, just as we may share their regrets at the perfectionism that made it difficult for him to bring a work of art to a successful conclusion, but contemporaries generally had no doubts about the genius of Leonard da Vinci. Naturally, in that era of classical revival, he was often compared with the great scholars of ancient Greece, with Archimedes, Pythagoras, and most of all, perhaps, Plato, whose figure in Raphael’s famous painting of the School of Athens is generally believed to be modeled on the venerable Leonardo. The life and work of Leonardo, the archetypical “Renaissance Man” for whom no branch of knowledge was allowed to remain a closed book, has proved endlessly fascinating to later generations. At one time, he was known only as a painter, although many of his works were unknown, and a number of inferior works by other hands were wrongly attributed to him. The full, amazing extent of his genius emerged only in quite recent times with the rediscovery of his notebooks and drawings. For a time, even Leonardo the painter seemed to be submerged by the weight of his new reputation as a scientist. Some readjustment has taken place since then. As a scientist and engineer, Leonardo’s achievements, though staggering enough, have proved to be a shade less novel than once we thought, while at the same time a succession of brilliant art historians, beginning with Bernhard Berenson and Kenneth Clark, have made us far more knowledgeable about his art. Though Leonardo would have chafed at such a judgment, he was and is, first and foremost, a great painter, a man whose output was tiny, compared with other geniuses of his time (a Michelangelo, a Raphael, a Titian) yet includes possibly the two most famous paintings in history: the Mona Lisa and the Last Supper.