Fritjof Capra (35 page)

From his thorough investigations of the brain and the nervous system, Leonardo concluded that the soul evaluated sensory impressions and transferred them to the memory, and that it was also the origin of voluntary bodily movement, which he associated with reason and judgment.

In Leonardo’s view, all material movement originated in the immaterial and invisible movements of the soul. “Spiritual movement,” he reasoned, “flowing through the limbs of sentient animals, broadens their muscles. Thus broadened, these muscles become shortened and draw back the tendons that are connected to them. This is the origin of force in the human limbs…. Material movement arises from theimmaterial.”
⁴²
With this concept of the soul, Leonardo expanded the traditional Aristotelian idea according to his empirical evidence. In this, he was far ahead of his time.

During the subsequent centuries, Leonardo’s Notebooks remained hidden in ancient European libraries and many of them were lost, and the integrated Aristotelian view of the soul gradually disappeared from philosophy. The idea of spirit as a disembodied divine principle became the dominant theme of religious metaphysics, and the soul, accordingly, was seen as being independent from the body and endowed with immortality. For other philosophers, the concept of the soul became increasingly synonymous with that of the rational mind, and in the seventeenth century, René Descartes postulated the fundamental division of reality into two independent and separate realms—that of mind, the “thinking thing”
(res cogitans)
, and that of matter, the “extended thing”
(res extensa)
.

This conceptual split between mind and matter has haunted Western science and philosophy for more than three hundred years. Following Descartes, scientists and philosophers continued to think of the mind as an intangible entity and were unable to imagine how this “thinking thing” is related to the body. In particular, the exact relationship between mind and brain is still a mystery to most psychologists and neuroscientists.

During the last two decades of the twentieth century, however, a novel conception of the nature of mind and consciousness emerged in the life sciences, which finally overcame the Cartesian division between mind and body. The decisive advance has been to reject the view of mind as a thing; to realize that mind and consciousness are not entities but processes. In the past twenty-five years the study of mind from this new perspective has blossomed into a rich interdisciplinary field known as cognitive science, which transcends the traditional frameworks of biology, psychology, and epistemology.
⁴³

Figure 9-4: Study of the anterior muscles of the leg, c. 1510, Anatomical Studies, folio 151r

One of the central insights of cognitive science is the identification of cognition, the process of knowing, with the process of life. Cognition, according to this view, is the organizing activity of living systems at all levels of life. Accordingly, the interactions of a living organism—plant, animal, or human—with its environment are understood as cognitive interactions. Thus life and cognition become inseparably connected. Mind—or, more accurately, mental activity—is immanent in matter at all levels of life. This new conception represents a radical expansion of the concept of cognition and, implicitly, the concept of mind. In the new view, cognition involves the entire process of life—including perception, emotion, and behavior—and does not even necessarily require a brain and a nervous system.

It is evident that the identification of mind, or cognition, with the process of life, although a novel idea in science, comes very close to Leonardo’s concept of the soul. Like Leonardo, modern cognitive scientists see cognition (or the soul) both as the process of perception and knowing and as the process that animates the movements and organization of the body. There is a conceptual difference. Whereas cognitive scientists understand cognition clearly as a process, Leonardo saw the soul as an entity. However, when he wrote about it, he always described it in terms of its activities.

How close Leonardo’s conception of the soul comes to the modern concept of cognition can be seen in his notes on the flight of birds, in which he compares the movements of the living bird with those of the flying machine he is designing. Over many hours of intense observations of birds in flight in the hills surrounding Florence, Leonardo became thoroughly familiar with their instinctive capacity to maneuver in the wind, keeping their equilibrium by responding to changing air currents with subtle movements of their wings and tails.
⁴⁴

In his notes, he explained that this capacity was a sign of the bird’s intelligence—a reflection of the actions of its soul.
⁴⁵
In modern scientific language, we would say that a bird’s interactions with the air currents and its delicate maneuvers in the wind are cognitive processes, as Leonardo clearly recognized and accurately described. He also realized that these delicate cognitive processes of a bird in flight would always be superior to those of a human pilot steering a mechanical device:

It could be said that such an instrument designed by man is lacking only the soul of the bird, which must be counterfeited with the soul of the man…. [However], the soul of the bird will certainly respond better to the needs of its limbs than would the soul of the man, separated from them and especially from their almost imperceptible balancing movements.
⁴⁶

Following Aristotle, Leonardo saw the soul not only as the source of all bodily movements, but also as the force underlying the body’s formation. He called it “the composer of the body.”
⁴⁷
This is completely consistent with the views of today’s cognitive scientists who understand cognition as a process involving the self-generation and self-organization of living organisms.

The main difference between Leonardo’s concept of the soul and modern cognitive science seems to be that Leonardo gave the human soul a specific location in the brain. Today we know that reflective consciousness—the special kind of cognition that is characteristic of the great apes and humans—is a widely distributed process involving complex layers of neural networks. Without access to the brain’s microscopic structures, chemistry, and electromagnetic signals, Leonardo had no way of discovering these extended networks of neurons; and since he observed that the pathways of various sensory nerves seem to converge toward the brain’s central ventricle, he decided that this had to be the seat of the soul.

At the time of the Renaissance, there was no agreement about the soul’s location. Whereas Democritus and Plato had recognized the importance of the brain, Aristotle regarded the heart as the seat of the
sensus communis
. Averroës, the great Arab commentator on Aristotle whose teachings were very influential in Italy during the Renaissance,
⁴⁸
had expounded yet another view. He identified the soul with the form of the entire living body, which meant that it did not have a specific location. Leonardo, after considering such opinions, in view of the empirical evidence he had gathered, confidently located the soul in the central cavity of the brain.

Body and soul formed one indivisible whole for Leonardo. “The soul desires to stay with its body,” he explained, “because without the organic instruments of that body it can neither carry out nor feel anything.”
⁴⁹
Again, this is completely consistent with modern cognitive science, where we have come to understand the relationship between mind and body as one between (cognitive) process and (living) structure, which represent two complementary aspects of the phenomenon of life. Indeed, as Leonardo wrote of the soul, so cognitive scientists today speak of the mind as being fundamentally embodied. On the one hand, cognitive processes continually shape our bodily forms, and on the other, the very structure of reason arises from our bodies and brains.
⁵⁰

Remarkably, for his time, Leonardo repeatedly argued against the existence of disembodied spirits. “A spirit can have neither voice, nor form, nor force,” he declared. “And if anyone should say that, through air collected together and compressed, a spirit assumes bodies of various forms, and by such instrument speaks and moves with force, to that I reply that, where there are neither nerves nor bones, there can be no force exerted in any movement made by such imaginary spirits.”
⁵¹

In Leonardo’s view, the essential unity of body and soul arises at the very beginning of life, and it dissolves with the demise of both at death. On the two folios that contain his most beautiful drawings of the human embryo in the womb (Fig. E-1), we find the following inspired thoughts on the relationship between the souls of mother and child:

One and the same soul governs these two bodies; and the desires, fears and pains are common to this creature as to all other animated parts…. The soul of the mother…in due time awakens the soul which is to be its inhabitant. This at first remains asleep under the guardianship of the soul of the mother who nourishes and vivifies it through the umbilical vein.
⁵²

This extraordinary passage is completely compatible with modern cognitive science. In poetical language, the artist and scientist describes the gradual development of the embryo’s mental life together with its body. At the end of life, the reverse process takes place. “While I thought I was learning how to live, I have been learning how to die,” Leonardo wrote movingly late in his life.
⁵³
In a striking departure from Christian doctrine, Leonardo da Vinci never expressed a belief that the soul would survive the body after death.

A THEORY OF KNOWLEDGE

My last two chapters outline what amounts to an extensive theory of knowledge, testifying to Leonardo’s genius as an integrative, systemic thinker. Approaching perception and knowledge as a painter, he began by exploring the appearance of things to the eye, the nature of perspective, the phenomena of optics, and the nature of light. He not only used the ancient metaphor of the eye as the window of the soul, but took it seriously and subjected it to his empirical investigations, following the rays of the “pyramids of light” into the eye, tracing them through the lens and the eyeball to the optic nerve. He described how in that area, known today as the retina, the percussion of light rays generates sensory impulses, and he followed these sensory impulses along the optic nerve all the way to the “seat of the soul” in the central cavity of the brain.

Leonardo also developed a detailed theory of how the sensory impressions enter consciousness. He remained vague on how exactly the nerve impulses come under the influence of the intellect, memory, and imagination, glossing over the relationship between conscious experience and neurological processes. However, even today our leading neuroscientists can do no better.
⁵⁴

That Leonardo was able to develop a sophisticated and coherent theory of perception and knowledge based on empirical evidence but without any knowledge of cells, molecules, biochemistry, or electromagnetism is certainly extraordinary. Many facets of his explanations later became separate scientific disciplines, including optics, cranial anatomy, neurology, brain physiology, and epistemology. During the last decade of the twentieth century, these subjects began to converge again within the interdisciplinary field of cognitive science, showing striking similarities to Leonardo’s systemic conception of the process of knowing.

Once again, I cannot help but wonder how differently Western science would have developed if Leonardo had published his treatises during his lifetime, as he had intended. Galileo, Descartes, Bacon, and Newton—the giants of the Scientific Revolution—lived and worked in intellectual milieus that were much closer to that of the Renaissance than ours. I believe they would have understood Leonardo’s language and reasoning much better than we do today. These natural philosophers, as they were still called, struggled with the very same problems that occupied and fascinated Leonardo during his life, and for which he often found original solutions. How would they have incorporated his insights into their theories?

Alas, such questions have no answers. While Leonardo’s paintings had a decisive influence on European art, his scientific treatises remained hidden for centuries, disconnected from the development of modern science.

EPILOGUE

“Read me, O reader, if in my words you find delight”

L
eonardo’s science cannot be understood within the mechanistic paradigm of Galileo, Descartes, and Newton. Although he was a mechanical genius who designed countless machines, his science was not mechanistic. He fully recognized and extensively studied the mechanical aspects of the human and animal bodies, but he always saw them as instruments, used by the soul for the organism’s self-organization. Trying to understand those processes of self-organization—the growth, movements, and transformations of nature’s living forms—was at the very core of Leonardo’s science. It was a science of qualities and proportions, of organic forms shaped and transformed by underlying processes. Nature as a whole was alive and animated for Leonardo, a world in continual flux and development, in the macrocosm of the Earth as in the microcosm of the human body.

While his contemporaries deferred to the authorities of Aristotle and the Church, Leonardo developed and practiced an empirical approach to acquiring independent knowledge, which became known as the scientific method many centuries after him. It involved the systematic and careful observation of natural phenomena, ingenious experiments, the formulation of theoretical models, and many attempts at mathematical generalizations.

Leonardo used his empirical method—together with his exceptional powers of observation and his “sublime left hand”—to analyze, draw, and paint “with philosophic and subtle speculation…all the qualities of forms.”
¹
The records he left of his lifelong investigations are superb testimonies of both his art and his science.

In recent decades, scholars have given us comprehensive analyses of some areas of Leonardo’s science (albeit often from perspectives somewhat different from mine), while other areas remain largely unexplored. Leonardo’s entire corpus of anatomical studies has been analyzed in impressive detail in a magnificent book,
Leonardo da Vinci’s Elements of the Science of Man
, by the historian of medicine and Leonardo scholar Kenneth Keele.
²

Leonardo’s original contributions to landscape and garden design as well as his outstanding work in botany are discussed in great detail in an insightful volume by botanist William Emboden,
Leonardo da Vinci on Plants and Gardens
.
³
Unfortunately, there is no comparable volume about Leonardo’s voluminous writings on “the motion of the waters,” which include his pioneering studies of fluid flow, as well as his many original thoughts on the ecological dimension of water as the medium and nurturing fluid of life. His related geological observations, centuries ahead of their time, also remain largely unexplored.

Leonardo’s contributions to mechanics and engineering are discussed extensively in several books, including the beautiful volume on
Renaissance Engineers from Brunelleschi to Leonardo da Vinci
by science historian Paolo Galluzzi.
⁴
His precise observations and analyses of the flight of birds and his persistent attempts to design workable flying machines are evaluated in a captivating, richly illustrated monograph by science historian Domenico Laurenza,
Leonardo on Flight
.
⁵
However, no overall assessment of Leonardo’s wide-ranging works in architecture and engineering from the modern perspective of design has been offered so far.
⁶
This would certainly be a fascinating subject.

Leonardo’s studies of the living forms of nature began with their outward appearance and then turned to methodical investigations of their intrinsic nature. Life’s patterns of organization, its organic structures, and its fundamental processes of metabolism and growth are the unifying conceptual threads that interlink his knowledge of macro-and microcosm. Throughout his life he studied, drew, and painted the rocks and sediments of the Earth, shaped by water; the growth of plants shaped by their metabolism; and the anatomy of the animal body in motion. He used his scientific understanding of the forms of nature as the intellectual underpinning of his art, and he used his drawings and paintings as tools of scientific analysis. Thus Leonardo’s studies of nature’s living forms represent a seamless unity of art and science.

In the Italian Renaissance, it was not unusual to find painters who were also accomplished sculptors, architects, or engineers. The
uomo universale
was the great ideal of the time. Nevertheless, Leonardo da Vinci’s synthesis of art and science, and its brilliant applications in numerous fields of design and engineering, were absolutely unique. In subsequent centuries, Leonardo’s scientific concepts and observations were gradually rediscovered, and his vision of a science of organic forms reemerged several times in different epochs. Never again, however, was so much intellectual and artistic genius embodied in a single human being.

Leonardo himself never boasted about his unique talents and skills, and in his thousands of pages of manuscripts he never vaunted the originality of so many of his ideas and discoveries. But he was well aware of his exceptional stature. In the Codex Madrid, in the midst of extensive discussions of the laws of mechanics, we find two lines that can stand as his own definitive epitaph:

Read me, O reader, if in my words you find delight, for rarely in the world will one such as I be born again.
⁷

For over forty years, Leonardo relentlessly pursued his scientific explorations, driven by his restless and intense intellectual curiosity, his love of nature, and his passion for all living things. His magnificent drawings often reflect that passion with great delicacy and sensitivity. For example, his famous picture of a fetus in utero (Fig. E-1) is accompanied by several smaller sketches that liken the womb to the embryo sac of a flower, picturing the peeled-off layers of the uterine membranes in an arrangement of flower petals. The entire set of drawings vividly shows Leonardo’s tremendous care and respect for all forms of life. They exude a tenderness that is deeply moving.

Leonardo’s science was a gentle science. He abhorred violence and had a special compassion for animals. He was a vegetarian because he did not want to cause animals pain by killing them for food. He would buy caged birds in the marketplace and set them free, and would observe their flight not only with a sharp observational eye but also with great empathy. Browsing through the Notebooks, one may suddenly get the impression that a single bird has flown right onto the page while Leonardo was discussing something else, followed by a whole flock of fluttering creatures on the subsequent folios.
⁸

In the designs of his flying machines, Leonardo tried to imitate the flight of birds so closely that he almost gives the impression of wanting to become a bird. He called his flying machine
uccello
(bird), and when he drew its mechanical wings, he mimicked the anatomical structure of a bird’s wing so accurately and, one almost feels, lovingly, that it is often hard to tell the difference (see Fig. E-2).

Instead of trying to dominate nature, as Francis Bacon advocated in the seventeenth century, Leonardo’s intent was to learn from her as much as possible. He was in awe of the beauty he saw in the complexity of natural forms, patterns, and processes, and aware that nature’s ingenuity was far superior to human design. “Though human ingenuity in various inventions uses different instruments for the same end,” he declared, “it will never discover an invention more beautiful, easier, or more economical than nature’s, because in her inventions nothing is wanting and nothing is superfluous.”
⁹

This attitude of seeing nature as a model and mentor is now being rediscovered in the practice of ecological design. Like Leonardo da Vinci five hundred years ago, ecodesigners today study the patterns and flows in the natural world and try to incorporate the underlying principles into their design processes.
¹⁰
When Leonardo designed villas and palaces, he paid special attention to the movements of people and goods through the buildings, applying the metaphor of metabolic processes to his architectural designs.
¹¹
He also considered gardens as parts of buildings, always attempting to integrate architecture and nature. He applied the same principles to his designs of cities, viewing a city as a kind of organism in which people, material goods, food, water, and waste need to flow with ease for the city to be healthy.
¹²

Figure E-1: The fetus within the womb, c. 1510–12, Anatomical Studies, folio 198r

Figure E-2: Study for a mechanical wing imitating the wing of a bird, Codex sul volo, folio 7r

In his extensive projects of hydraulic engineering, Leonardo carefully studied the flow of rivers in order to gently modify their courses by inserting relatively small dams in the right places and at the optimal angles. “A river, to be diverted from one place to another, should be coaxed and not coerced with violence,” he explained.
¹³

These examples of using natural processes as models for human design, and of working with nature rather than trying to dominate her, show clearly that as a designer, Leonardo worked in the spirit that the ecodesign movement is advocating today. Underlying this attitude of appreciation and respect of nature is a philosophical stance that does not view humans as standing apart from the rest of the living world, but rather as being fundamentally embedded in, and dependent upon, the entire community of life in the biosphere.

Today this philosophical stance is promoted by a school of thought and cultural movement known as “deep ecology.”
¹⁴
The distinction between “shallow” and “deep” ecology is now widely accepted as a useful terminology for referring to a major division within contemporary environmental thought. Shallow ecology views humans as above or outside the natural world, as the source of all value, and ascribes only instrumental, or “use,” value to nature. Deep ecology, by contrast, does not separate humans—or anything else—from the natural environment. It sees the living world as being fundamentally interconnected and interdependent and recognizes the intrinsic value of all living beings. Amazingly, Leonardo’s Notebooks contain an explicit articulation of that view: “The virtues of grasses, stones, and trees do not exist because humans know them…. Grasses are noble in themselves without the aid of human languages or letters.”
¹⁵

Ultimately, deep ecological awareness is spiritual or religious awareness. When spirituality is understood as a way of being that flows from a deep sense of oneness with all, a sense of belonging to the universe as a whole, it becomes clear that ecological awareness is spiritual in its deepest essence.
¹⁶
It seems that Leonardo da Vinci’s view of the world had that kind of spiritual dimension. Unlike most of his contemporaries, he hardly ever referred to God’s creation, but preferred to speak of the infinite works and marvelous inventions of nature. The Notebooks are full of passages in which he describes how nature “has ordained” that animals should experience pain, how she has created stones, made the surface of the cornea convex, given movement to animals, and formed their bodies.