The Treatise on Painting that was printed in Paris in 1651 was one of art history’s great missed opportunities. It fostered a skewed view of Leonardo, and a version of the man that would prevail among readers for the next 150 years.
Nicolas Poussin, however, knew better.
He criticized the printed Treatise on Painting harshly, indifferent to the fact that the French editors were his personal friends and that they had singled him out as the “second author” of the book. Poussin knew Leonardo’s shadow drawings and had assimilated Leonardo’s teachings on shadows, colors, and reflections into his own practice like no other painter. He admired Leonardo so deeply that he had fashioned himself as a painter-philosopher after Leonardo’s example.
And so he was horrified by the illustrations for both the French and the Italian editions.
He could hardly recognize “the clumsy landscapes” that were situated behind the human figures he had drawn for Cassiano; these landscapes “were added by a certain Errard, without me having known anything about it.” For him, the printed treatise had little to recommend it: “[all] that is good in this book can be written on a sheet of paper in capital letters,” he wrote to a fellow artist.
And yet, apart from expressing his views in private letters, Poussin did not do much to promote a more comprehensive view of Leonardo. Nor did the publication of one of these critical letters in 1665, as part of a tract authored by another French artist, do much to rectify the situation.
In addition to Poussin, there were others who knew better, as they also had seen Leonardo’s shadow drawings. But despite holding prominent positions in the artistic circles of Paris and Rome, they could do little to reverse the damage inflicted by the printed Treatise.
In 1662, the treatise’s primary editor, Roland Fréart de Chambray, wrote a book titled The Idea of Perfection in Painting, in which he argued that Leonardo’s teachings and Poussin’s artistic practice should serve as guides for further developments in art. But even though he had seen the shadow drawings Poussin owned, he did not use them to substantiate his view or discuss Leonardo’s science of art explicitly.
A few years later, in 1665, his brother Paul Fréart de Chantelou became Gian Lorenzo Bernini’s official guide during the sculptor’s five-month Parisian sojourn. Chantelou described Bernini’s visit in a journal that has since become fundamental to our understanding of the court of Louis XIV. But Chantelou did nothing to disseminate knowledge of Leonardo’s science of art.
Errard became première peintre du roi after Poussin left Paris. He had been among the founders of the French art academy, and eventually became the first director of its branch in Rome, which opened in 1666. But he, too, did almost nothing to promote a more truthful view of Leonardo.
One particularly important figure in the history of Leonardo’s legacy is the art connoisseur André Félibien, who served the French court for over thirty years as a historian and secretary of a new royal academy for architecture. He wrote extensively on artistic subjects, including optics and aerial perspective, and promoted an aesthetic based on ancient art, Raphael, Poussin, and Leonardo. He was uniquely well informed about Poussin’s knowledge of optics. He also had a more comprehensive view of Leonardo, since he had received, directly from Cassiano in Rome in 1649, an updated copy of Cassiano’s master copy of the Book on Painting, and was also familiar with the shadow drawings. But he never acknowledged that he was indebted to Leonardo for his knowledge of aerial perspective.
In the meantime, Melzi’s Book on Painting lay buried in various libraries. At some point it ended up in the library of the court of Urbino, at the time one of the most famous in all of Europe. We do not know exactly when it arrived. Had it been there all along? Had it sojourned at smaller private libraries along the way, been sold at one point or another to improve the finances of its owners? Of one thing we are certain: when the ruling family of Urbino was unable to produce a male heir, the pope incorporated their lands into the papal states, and, as a result, the library’s contents were transferred to Rome in 1657.
At first, Melzi’s compilation was stored in the Biblioteca Universitaria Alessandrina, a beautiful library the Baroque architect Francesco Borromini had designed for Pope Alexander VII next to “La Sapienza,” the University of Rome. In later years, it was moved to the main Vatican Library, which was located in the Vatican palace. There, a low-level functionary cataloged a book on painting by Leonardo da Vinci.
Year after year, decade after decade, the Melzi edition sat quietly in the Vatican Library. Another 150 years would pass before a librarian named Guglielmo Manzi came to the rescue. He not only realized the value of the book in the Vatican’s possession but also saw to its publication. In 1817, the Melzi version of the Book on Painting finally appeared, with a brief introduction indicating that only “part of this treatise was published” in the past and that Leonardo’s “ideas will be complete for the first time.” Manzi offered no comparison of the authentic version with either the early hand-copied versions or with the printed Treatise, although he did say that these texts were “truncated and mutilated [tronco e smozzicato].” Nor did he investigate why this truncated version of the original had been created, or determine what exactly had been cut.
You might imagine that in the following decades scholars from all over the world would pore over Melzi’s Book on Painting and assess its contents and impact on Leonardo’s reputation. But shortly after the publication of the entire Book on Painting, over four thousand pages of Leonardo’s original papers—which had until then been scattered and buried in various private libraries—began to be published. Although these texts were extremely confusing, and it was impossible to get a clear sense of what Leonardo meant to say about painting from them, scholars concentrated on this new outpouring of work. After all, they were primary-source documents. No matter that Melzi had lived with Leonardo and learned about painting directly from him; no matter that it was Melzi to whom Leonardo had described his personal thoughts; no matter that it was Melzi to whom Leonardo willed his papers—Melzi’s edition could not be construed as a primary source.
And so it took over 150 more years for scholars to do the work of comparing Melzi’s version to the supposedly abridged versions. Only when this work was finally completed, in the 1950s and 1960s, did people understand that the “abridged” versions that were disseminated by way of handwritten copies and printed books were not just “abridged,” but in fact doctored—one might say travestied.
By this time, scholars had also completed significant research on Leonardo’s original notebooks, which were edited, annotated, and published in beautiful facsimile editions. This expert scholarship has also allowed us to develop a more holistic view of Leonardo, a view that Melzi had but that escaped the many who came after him.
Today, when we look at the layout of Leonardo’s folios, the content of his language, and the physical characteristics of the paper and ink, we are in a much better position than we were just a few decades ago to decode their meaning. We can determine with a good degree of certainty whether we are reading a passing thought the artist jotted down while on the move, words he copied from a book by another author as he read at his desk, a rough draft of an idea inspired by observations or an experiment, or a revised text based on earlier, messier drafts. We can access the notebooks worldwide thanks to the Internet. We can even imagine a day when advanced digital technology will take our knowledge of the artist even further. We will be able not only to consult Leonardo’s writings as they are preserved today—notebook by notebook, folio by folio—but also to “see” them as Leonardo kept them on his desk when he composed them. We will be able to virtually reassemble folios that are now dispersed across different libraries, but that Leonardo kept in the same set or notebook, and we will be able to study the detailed evolution of his thoughts over time. And we will be able to reorder according to Leonardo’s intentions folios that later owners assembled only randomly—including the folios that contain many of the shadow drawings.
The shadow drawings—and the knowledge required to create them—testify to Leonardo’s deep interest in the science of optics, “the soul of painting.” They also reveal the roots of Leonardo’s belief that “painting is philosophy,” and how those thoughts took shape in his mind from a young age. They form part of the growing body of evidence that is helping us revise the traditional view that science came to play a role in Leonardo’s thinking only after his artistic vision was formed. Today, it seems more and more plausible that Leonardo had been steeped in philosophy and science since his youth, and that he started to read and write at a young age, although admittedly not much of what he wrote as a young man has survived. A new understanding of the artist is slowly emerging: Leonardo became the painter he became because his artistic training involved traditional workshop instruction and a deep engagement with optics and philosophy. The stunning optical effects that are a defining characteristic of even Leonardo’s early work can be connected with his shadow drawings—which, in turn, were made possible by the people he met in his youth, the places he lived, the books he read, and, not least of all, the master who trained him and who designed the golden palla atop Florence’s cathedral.
The shadow drawings also help us to understand why, for Leonardo, painting was a means of investigating the natural world—or, as he put it, “a subtle invention, which with philosophical and subtle speculation considers all manner of forms: sea, land, trees, animals, grasses, flowers, all of which are enveloped in light and shade.” When he eventually delved into geology, botany, zoology, optics, and the study of water, he did so because all these fields also pertained to painting. At times, these other subjects took over his life entirely. Others were lifelong interests to which he returned intermittently. All, though, were subordinate to painting.
His unparalleled artistic skills allowed him to make visible complex bodies of knowledge, complex interrelations between humans and nature. He explored abstract concepts from geology, hydraulics, philosophy, physics, and optics, and he translated them into images and diagrams, based in part on what he read in books but also what he saw with his own eyes. He never ceased thinking about the world the way artists do, in visual terms. He always remained an artist, and especially a painter, first and foremost—a painter who happened to believe that “painting is philosophy.”
Yet the shadow drawings also force us to rethink what is perhaps the most commonly held belief about Leonardo: that for him, art was about copying the appearance of nature, what he called the “ornaments of the world”—sea, land, trees, animals, grasses, flowers. It wasn’t. Before the word “psychology” was invented, before empathy existed as a concept, before neuroscientists discovered the neural basis of our ability to feel what others feel, Leonardo was determined to be the artist who took Renaissance painting where it had never gone before—into the inner, invisible worlds of its subjects. He understood that the subtlest change of heart or mind involuntary triggered an alteration in the appearance of bodies and faces, and that what made these minute shifts visible were the unexpected shadows cast by human figures exposed to light.
This is why the final result of Leonardo’s inquiry was not a book (he drafted many and finished none), or an experiment (though he performed many and designed even more), or even a drawing (though he drew compulsively). The final result was always an oil painting. Because only at an easel, practicing his technique at the highest level, could he capture the variations of light and shadow on people’s faces and bodies, which in turn revealed the subtlest movements of muscles and tendons, which in turn revealed changes in their states of mind. The medium—oil painting—was integral to the idea itself.
This integrated approach to painting, philosophy, and science lay at the heart of Leonardo’s project. And yet we find it easier to simply marvel at the work of “his hand” than to understand this work as the lost way of comprehending the world that it in fact is.
The news that a painting recently attributed to Leonardo was bought for $450 million (the highest price ever paid for a work of art at auction) made headlines worldwide. And the collective gasp grew only louder when the painting’s unveiling at the Louvre Abu Dhabi was canceled without explanation, before the work disappeared from public view altogether. Sensational discoveries of new works by Leonardo are announced every once in a while—to discover a “new” Leonardo is the holy grail of art history. Meanwhile, old works seem to only be growing in fame. The Mona Lisa was the backdrop of a video by Beyoncé and Jay-Z that instantly reached millions of viewers. The fascination with Leonardo reached a peak in 2019, the year that marked the five hundredth anniversary of the artist’s death. Today, we place Leonardo and his paintings in such a gilded frame (sometimes literally) that we often miss their true value.
But those among his contemporaries who knew him had a very clear sense of what made his art great—the shadow drawings and the philosophical and scientific knowledge that informed them. As the doctor-scholar Paolo Giovio said of Leonardo, “[Nothing] was more important to him than the rules of optics, which he followed to study the principles of light and shadow exactly and minutely.”
Any educated person in the Renaissance would have heard the ancient myth that the first painting was born from a shadow. Pliny recounted it, countless other authors repeated it, and Leonardo jotted it down in a note that he intended for his book on painting: “The first painting was merely a line drawn round a shadow of a man cast by the sun upon a wall,” he wrote. But unlike the authors who came before him, who were either silent about the source of light that generated this mythical shadow or mentioned a torch or a candle, Leonardo specified that it was “cast by sun.” Painting was about depicting outdoor shadows generated by sunlight and by the universal light of the sky—shadows that “seem to have no end [che paia senza fine].” His sfumato technique originated in these natural shadows, and was his means of situating his figures in relation to one another, to the viewer, and to the cosmos. No fixed boundaries divided people from one another, from objects, or from nature. Painting was a technique for revealing the human soul that existed in such a universe—and doing so by way of light and shadow. That’s what art—and the science that informed it—could accomplish. And for Leonardo, that was enough.