The Science of Leonardo: Inside the Mind of the Great Genius of the Renaissance

by Fritjof Capra

  Leoni also sold several complete Notebooks. Twelve of those were eventually given to the Ambrosiana Library; others disappeared. Pages were torn from some and ended up in various European libraries and museums. One collection, acquired in 1750 by Prince Trivulzio and known as Codex Trivulzianus, is now in the Trivulziana Library in Milan, which bears the name of the prince’s family.

  By the eighteenth century, Leonardo’s manuscripts were in great demand, especially among English art collectors. Lord Lytton purchased three bound Notebooks and later sold them to a certain John Forster, who in turn bequeathed them to the Victoria and Albert Museum. They are now known as Codices Forster I, II, and III. Another complete Notebook, which had been obtained directly from Orazio Melzi, passed through the hands of a succession of Italian artists before it was bought by the Earl of Leicester, and thus acquired the name Codex Leicester.

  When Napoleon Bonaparte entered Milan in 1796 at the height of his Italian campaign, he ordered, with an imperial gesture, the transfer of all the Notebooks from the Ambrosiana Library to Paris. The Codex Atlanticus was later returned to the Ambrosiana, but the twelve complete Notebooks remained at the Bibliothèque Nationale in Paris, where they have been designated by the initials A–M (excluding J).

  In the mid-nineteenth century, Guglielmo Libri, professor of mathematics and historian of science, stole several folios from Manuscripts A and B at the Bibliothèque Nationale. He also removed the small Codice sul volo degli uccelli (Codex on the Flight of Birds), which had been attached to Manuscript B. After the theft, Libri fled to England where he assembled the single folios into two collections and sold them to Lord Ashburnham. Eventually they were returned to Paris and reattached to Manuscripts A and B. Nonetheless, they are still known today as Ashburnham I and II. The Codex sul volo was disassembled by Libri. Its pieces passed through several hands, including those of the Russian prince Theodore Sabachnikoff, who donated the pieces to the Royal Library in Turin, where the entire codex was finally reassembled.

  In 1980 the Codex Leicester was sold at auction by the heirs of the earl. It was bought by the American petroleum magnate and collector Armand Hammer, who renamed it Codex Hammer. After Hammer’s death, the codex was auctioned again and was bought by the software billionaire Bill Gates. Gates restored the original name, Codex Leicester, but then proceeded to cut up the Notebook into individual pieces in the fashion of Leoni and other wealthy art collectors.

  The Codex Leicester is the only Notebook remaining in private possession today. The other manuscripts—Notebooks in their original bound forms of various sizes, the large artificial collections, torn pages, and isolated folios—are all housed in libraries and museums. More than half of the original manuscripts have been lost, although some may still exist, gathering dust unseen in private European libraries. Indeed, two complete Notebooks were discovered in the labyrinth of the stacks in the National Library in Madrid as recently as 1965. Designated Codices Madrid I and II, they brought to light many previously unknown aspects of Leonardo’s works, including studies in mathematics, mechanical and hydraulic engineering, optics, and perspective, as well as inventories of Leonardo’s personal library.94

  While Leonardo’s paintings have been admired by countless art lovers during his lifetime and throughout the centuries, his Notebooks came fully to light only in the late nineteenth century, when they were finally transcribed and published. Today the writings of this brilliant pioneer of modern science are available to scholars in excellent facsimile editions and clear transcriptions. His scientific and technical drawings are frequently exhibited today, sometimes supplemented by wooden models of the machines he designed. Nevertheless, more than five hundred years after his birth, the science of Leonardo is still not widely known, and is often misunderstood.

  FIVE

  Science in the Renaissance

  To appreciate Leonardo’s science, it is important to understand the cultural and intellectual context in which he created it. Scientific ideas do not occur in a vacuum. They are always shaped by cultural perceptions and values, and by the technologies available at the time. The entire constellation of concepts, values, perceptions, and practices—the “scientific paradigm” in the terminology of science historian Thomas Kuhn—provides the context that is necessary for scientists to pose the great questions, organize their subjects, and define legitimate problems and solutions.1 All science is built upon such an intellectual and cultural foundation.

  Hence, when we recognize ancient or medieval ideas reflected in Leonardo’s scientific writings, this does not mean that he was less of a scientist, as has sometimes been asserted. On the contrary: Like every good scientist, Leonardo consulted the traditional texts and used their conceptual framework as his starting point. He then tested the traditional ideas against his own scientific observations. And, in accordance with scientific method, he did not hesitate to modify the old theories when his experiments contradicted them.

  THE REDISCOVERY OF THE CLASSICS

  Before we examine how Leonardo developed his scientific method, we need to understand the principal ideas of ancient and medieval natural philosophy, which formed the intellectual context within which he operated.2 Only then will we be able to truly appreciate the transformative nature of his accomplishments.

  The ideas of Greek philosophy and science, on which the Renaissance worldview was based, were ancient knowledge. Yet for Leonardo and his contemporaries, they were fresh and inspiring, because most of them had been lost for centuries. They had been rediscovered only recently in the original Greek texts and in Arabic translations. As the Italian humanists studied a wide variety of classical texts and their Arabic elaborations and critiques, the Renaissance rediscovered the classics, as well as the concept of critical thinking.

  During the Early Middle Ages (sixth through tenth centuries A.D.), also known as the Dark Ages, Greek and Roman literature, philosophy, and science were largely forgotten in Western Europe. But the ancient texts had been preserved in the Byzantine Empire, along with the knowledge of classical Greek.3 And so the Italian humanists repeatedly journeyed to the East, where they acquired hundreds of classical manuscripts and brought them to Florence. They also established a chair of Greek at the Studium Generale, as the University of Florence was called, and attracted eminent Greek scholars to help them read and interpret the ancient texts.

  In antiquity, the Romans were in awe of Greek art, philosophy, and science, and their noble families often employed Greek intellectuals as tutors for their children. But the Romans themselves hardly produced any original science. However, Roman architects and engineers wrote many important treatises, and Roman scholars condensed the scientific legacy of Greece into large encyclopedias that were popular during the Middle Ages and the Renaissance. These Latin texts were eagerly consulted by the humanist artists and intellectuals, and some were translated into the Italian vernacular.

  In the seventh century, powerful Muslim armies, inspired by the new religion of Islam, burst forth from the Arabian peninsula and in successive invasions conquered peoples in the Middle East, across North Africa, and in southern Europe. As they built their vast empire, they not only spread Islam and the Arabic language, but also came in contact with the ancient texts of Greek philosophy and science in the Byzantine libraries. The Arabs deeply appreciated Greek learning, translated all the important philosophical and scientific works into Arabic, and assimilated much of the science of antiquity into their culture.

  In contrast to the Romans, the Arab scholars not only assimilated Greek knowledge but examined it critically and added their own commentaries and innovations. Numerous editions of these texts were housed in huge libraries throughout the Islamic empire. In Moorish Spain, the great library of Córdoba alone contained some six hundred thousand manuscripts.

  When the Christian armies confronted Islam in their military crusades, their spoils often included the works of Arab scholars. Among the treasures left behind by the Moors in Toledo when they retreated w
as one of the finest Islamic libraries, filled with precious Arabic translations of Greek scientific and philosophical texts. The occupying forces included Christian monks, who quickly began to translate the ancient works into Latin. A hundred years later, by the end of the twelfth century, much of the Greek and Arabic philosophical and scientific heritage was available to the Latin West.

  Islamic religious leaders emphasized compassion, social justice, and a fair distribution of wealth. Theological speculations were seen as being far less important and therefore discouraged.4 As a result, Arab scholars were free to develop philosophical and scientific theories without fear of being censored by their religious authorities.

  Christian medieval philosophers did not enjoy such freedom. Unlike their Arab counterparts, they did not use the ancient texts as the basis for their own independent research, but instead evaluated them from the perspective of Christian theology. Indeed, most of them were theologians, and their practice of combining philosophy—including natural philosophy, or science—with theology became known as Scholasticism. While early Scholastics, led by Saint Augustine, attempted to integrate the philosophy of Plato into Christian teachings, the height of the Scholastic tradition was reached in the twelfth century, when the complete writings of Aristotle became available in Latin, usually translated from Arabic texts. In addition, the commentaries on Aristotle by the great Arab scholars Avicenna (Ibn Sina) and Averroës (Ibn Rushd) were translated into Latin.

  The leading figure in the movement to weave the philosophy of Aristotle into Christian teachings was Saint Thomas Aquinas, one of the towering intellects of the Middle Ages. Aquinas taught that there could be no conflict between faith and reason, because the two books on which they were based—the Bible and the “book of nature”—were both authored by God. Aquinas produced a vast body of precise, detailed, and systematic philosophical writings in which he integrated Aristotle’s encyclopedic works and medieval Christian theology into a magnificent whole.

  The dark side of this seamless fusion of science and theology was that any contradiction by future scientists would necessarily have to be seen as heresy. In this way, Thomas Aquinas enshrined in his writings the potential for conflicts between science and religion—which indeed arose three centuries later in Leonardo’s anatomical research,5 reached a dramatic climax with the trial of Galileo, and have continued to the present day.

  THE INVENTION OF PRINTING

  The sweeping intellectual changes that took place in the Renaissance and prepared the way for the Scientific Revolution could not have happened without a technological breakthrough that changed the face of the world—the invention of printing. This momentous advance, which took place around the time of Leonardo’s birth, actually involved a double invention, that of typography (the art of printing from movable type) and that of engraving (of printable pictures). Together, these inventions marked the decisive threshold between the Middle Ages and the Renaissance.

  Printing introduced two fundamental changes to the distribution of texts: rapid diffusion and standardization. Both were of tremendous importance for the spread of scientific and technological ideas. Once a page had been composed by the typesetters, it was easy to produce and distribute hundreds or thousands of copies. Indeed, after Johannes Gutenberg printed his famous forty-two-line Bible in Mainz around 1450, the art of printing spread across Europe like wildfire. By 1480 there were over a dozen printers in Rome, and by the end of the century Venice boasted around one hundred printers, who turned this city of great wealth into the foremost printing center of Europe. It has been estimated that the Venetian printers alone produced about 2 million volumes during the fifteenth century.6

  For the rise of science, the production of standard texts was as important as their wide dissemination. With the use of the printing press, texts could not only be copied exactly, but were also laid out identically in each copy, so that scholars in different geographical locations could refer to a particular passage on a specific page without ambiguity. This had never been easy, nor dependable, in hand-copied medieval manuscripts.

  The production of standard copies of images that served as illustrations of texts was perhaps even more important, and this is where the invention of engraving became an indispensable complement to typography. Whereas the pictures in ancient manuscripts often lost detail with each new manual copy, the use of woodcuts and copper plates now made it possible to reproduce illustrations of plants, anatomical details, mechanical devices, scientific apparatus, and mathematical diagrams with complete accuracy. Those images were valuable standards to which scholars could easily refer.

  Leonardo was well aware of these tremendous advantages of printing and keenly interested in the technical details of the printing process throughout his life.7 Among his earliest drawings of mechanical devices in the Codex Atlanticus, from the years 1480–82, is one of a typographic press with an automatic page feeder, an innovation that was to reappear a couple of decades later. As he expanded his scientific research, Leonardo became increasingly aware of the need to disseminate printed versions of his treatises. Around 1505, while he painted The Battle of Anghiari in Florence and wrote his Codex on the Flight of Birds, he even invented a novel printing method for the simultaneous reproduction of texts and drawings. This was an extraordinary forerunner of the method introduced in the late eighteenth century by the Romantic poet and artist William Blake, who was also a professional engraver.8

  Figure 5-1: The vertebral column, c. 1510, Anatomical Studies, folio 139v

  A few years later, at the height of his anatomical work in Milan, Leonardo added a technical note about the reproduction of his drawings to his famous assertion of the superiority of drawing over writing.9 He insisted that his anatomical drawings should be printed from copper plates, which would be more expensive than woodcuts but much more effective in rendering the fine details of his work. “I beg you who come after me,” he wrote on the sheet that contains his magnificent drawings of the vertebral column (Fig. 5-1), “not to let avarice constrain you to make the prints in [wood].”10

  THE WORLD OF EXPLORATION

  While explorations of the rediscovered classical texts greatly extended the intellectual frontiers of the Italian humanists, their physical frontiers were also being extended by the geographical discoveries of the famous Portuguese explorers and those who followed them. The Renaissance was the golden age of geographical exploration. By 1600 the surface of the known world had doubled since medieval times. Entirely new regions, new climates, and new aspects of nature were being discovered. These explorations generated a strong interest in biology, or “natural history” as it was called at the time, and the great ocean voyages led to numerous improvements in shipbuilding, cartography, astronomy, and other sciences and technologies associated with navigation.

  In addition to the explorers’ seafaring voyages, new regions of the Earth were being discovered, even in the very heart of Europe when the first mountaineers ventured into the higher altitudes of the Alps. During the Middle Ages it had been commonly believed that the high mountains were dangerous, not only because of the severity of their climates but also because they were the abodes of gnomes and devils. Now, with the new humanist curiosity and confidence in human capabilities, the first Alpine expeditions were being undertaken, and by the end of the sixteenth century, close to fifty summits had been reached.11

  Leonardo fully embraced the humanist passion for exploration, in both the physical and mental realms. He was one of the first European mountaineers12 and traveled frequently within Italy, exploring the vegetation, waterways, and geological formations of the regions he visited. In addition, he delighted in composing fictitious tales of journeys to mountains and deserts in faraway countries.13

  These few examples from Leonardo’s many interests and activities show us that he was well aware of the intellectual, technological, and cultural achievements of his time. From his early days as an apprentice in Verrocchio’s workshop through the years he spent at var
ious European courts, he was in regular contact with leading artists, engineers, philosophers, historians, and explorers, and thus thoroughly familiar with the wide range of ideas and practices that we now associate with the Renaissance.

  THE ANCIENT VIEW OF THE UNIVERSE

  The foundation of the Renaissance worldview was the conception of the universe that had been developed in classical Greek science: that the world was a kosmos, an ordered and harmonious structure. From its beginnings in the sixth century B.C., Greek philosophy and science understood the order of the cosmos to be that of a living organism rather than a mechanical system. This meant that all its parts had an innate purpose to contribute to the harmonious functioning of the whole, and that objects moved naturally toward their proper places in the universe. Such an explanation of natural phenomena in terms of their goals, or purposes, is known as teleology, from the Greek telos (purpose). It permeated virtually all of Greek philosophy and science.

  The view of the cosmos as an organism also implied for the Greeks that its general properties are reflected in each of its parts. This analogy between macrocosm and microcosm, and in particular between the Earth and the human body, was articulated most eloquently by Plato in his Timaeus in the fourth century B.C., but it can also be found in the teachings of the Pythagoreans and other earlier schools. Over time, this idea acquired the authority of common knowledge, which continued throughout the Middle Ages and into the Renaissance.