Before Freud and neuroscience, it took centuries to dare to look inside the human skull. Here’s how we moved from the immaterial soul to the observed, dissected, and mapped brain.
Before Freud and neuroscience, it took centuries to dare to look inside the human skull. Here’s how we moved from the immaterial soul to the observed, dissected, and mapped brain.
For centuries, the great question has not been how the brain works, but where the soul resides. Medieval scholasticism, this Christian philosophy that closely unites theology and reason between the 9th and 16th centuries, made it its favorite battleground.
Saint Thomas Aquinas, for example, describes an immaterial soul unique to humans, endowed with sensitivity, imagination, memory, and above all, reason, the latter faculty radically distinguishing him from animals (which, according to him, possess only sensitivity, imagination, memory, and estimation). For him, knowledge always begins with the sensible, but it is intelligence that draws out an intelligible form from it.
In contrast, Averroes asserts that the soul is simply the form of the body, an idea deemed so disturbing that it was banned at the University of Paris in 1215. This tension between the separated soul and the soul incarnated in matter would weigh heavily on the way one dares, or does not dare, to open a body to study its interior.
It is in this climate that the Renaissance makes a decisive shift. People no longer content themselves with discussing the soul in books; they want to see, touch, and understand the body that houses it. Ambroise Paré, a surgeon, and Leonardo da Vinci, a jack-of-all-trades fascinated by human anatomy, embody this new appetite for direct observation.
This turning point is not isolated. Thinkers like Giordano Bruno confront the Aristotelian logic that had dominated minds until then, while Montaigne invents an entire literary genre dedicated to the study of man by himself, summarized in his famous "What do I know?". Humanity finally becomes a legitimate object of study, no longer just a subject of theological speculation.
This new curiosity about the body, particularly what lies beneath the skull, paves the way for centuries of discoveries. It marks the moment when the question "what is the soul" slowly begins to transform into "how does the brain work."
Observing is not enough to understand. Even today, with far more sophisticated means, the brain remains a complex machine whose mysteries scientists are still probing. So imagine in the 16th century, without a proper microscope or a theory of neuronal functioning.
The first anatomists of the Renaissance could describe the shapes, folds, and coverings of the organ, but they had no way to explain how this gray matter produced thought, memory, or emotion. The gap between seeing and understanding remained immense.
This disconnect between visible anatomy and the invisible workings of the mind would fuel philosophical reflection for several more centuries. It would take modern physiology, and then psychoanalysis, for this mystery to begin to unravel a bit.
The shift in vocabulary is not trivial. Where the Middle Ages spoke of the soul, the philosophers of the 17th century began to speak of consciousness, a concept closer to lived experience than to religious dogma. Descartes paves the way with his famous "I think, therefore I am," where the self becomes synonymous with pure thought, grasped by immediate intuition.
Leibniz, for his part, imagines units called monads, classified from the simplest, devoid of consciousness, to the human soul, which possesses true consciousness, with God representing the ultimate infinite consciousness. This is a very original way of grading levels of consciousness throughout nature.
Later, Rousseau, in his work on education, defines consciousness as the "infallible judge of good and evil, which makes man similar to God." It is clear here that the word has changed meaning: it is no longer a divine breath lodged somewhere in the body, but an inner faculty of judgment and self-perception.
Specifically, what are we talking about when we mention the brain? It consists of about 1.4 kg of gray matter that controls thought, emotions, memory, and sends its commands to the rest of the body through nerve impulses. This organ is part of a larger system, the nervous system, which also includes the spinal cord and a network of nerves.
The basic unit of this system is the neuron. Each neuron has dendrites, branches responsible for capturing information, and a single, longer axon that transmits this information to the next neuron. The point of contact between two neurons is called a synapse, where nerve impulses travel in the form of chemical or electrical exchanges.
These neurons do not work alone. They are surrounded and supported by glial cells, which protect them, nourish them, and remove their waste. To give an idea of the proportions: there are about 100 billion neurons in the brain, surrounded by 50 to 100 times more glial cells.
The brain does not form a uniform mass; it is divided into several well-defined lobes. The frontal lobe occupies the front of the skull, the parietal lobe is located at the top, the occipital lobe is at the back, and on each side are the temporal lobes, right and left.
This organization into distinct areas is not just an anatomical curiosity. It corresponds to a functional specialization that anatomists have taken centuries to understand, with each region participating in different tasks in information processing.
The brain communicates with the rest of the body through the medulla oblongata, a sort of junction that connects it to the spinal cord. The spinal cord, safely housed within the spinal canal inside the vertebrae, resembles a small flattened sausage about 0.5 centimeters in diameter and serves as a transmission pathway in both directions: commands from the brain descend to the body, while sensory information ascends to it.
How do sensations reach the brain? Through nerve fibers, these chains of neurons commonly known as nerves. When we prick or burn ourselves, the information travels from the nerves to the spinal cord, which in turn transmits it to the brain, explaining the slight delay of a few microseconds before the pain is truly felt.
The eye presents an interesting exception: directly connected to the brain, it transmits information almost instantaneously, unlike other nerve endings that are farther away. This simple detail illustrates how each sense has its own transmission circuit to the brain's command center.
Philosophically, this question of the senses had already occupied medieval thinkers. Saint Thomas Aquinas, for example, limited the animal soul to sensitivity, imagination, memory, and estimation, while the human soul added reason, the ability to establish connections between ideas rather than merely receiving them through the senses.
If anatomy has ultimately mapped the brain with considerable precision, consciousness still resists any simple localization. Kant already distinguished between knowledge that comes from experience and that which is said to be a priori, existing independently of it, a way of saying that not everything can be reduced to what the senses provide us.
Husserl, the founder of phenomenology, emphasized that "consciousness is always consciousness of something," rejecting the idea of a subject completely detached from its experience. Sartre would take up this idea by distinguishing being-in-itself, that of things, and being-for-itself, that of consciousness, which never quite coincides with itself.
What is striking is that even modern science, long after these philosophers, continues to search for where and how consciousness emerges from brain matter. The mystery glimpsed by the early anatomists of the Renaissance has therefore never been completely resolved; it has simply changed form.
With Freud, at the turn of the 20th century, everything changes completely. He starts from the premise that each of us is governed by processes of which we are not the conscious agents, obscure but very real laws that govern our behaviors as much as natural phenomena.
His theory distinguishes three instances: the id, an unconscious drive pole present from birth; the ego, which is constructed through contact with the external world; and the superego, shaped by education and internalized prohibitions. To access this buried unconscious, Freud uses the interpretation of dreams, slips of the tongue, and missed acts—those little failures of everyday life that betray our repressed drives.
This approach owes much to Joseph Breuer, who was already working on hysteria using the cathartic method, which involved putting the patient under hypnosis to help them discover the origin of their symptoms. Freud would abandon hypnosis in favor of simple recollection, inviting the patient to freely say whatever comes to mind, thus laying the foundations of modern psychoanalysis.
A few decades later, Henri Bergson proposed a completely different way of approaching consciousness, very far from the prevailing scientism of his time. In his "Essay on the Immediate Data of Consciousness," published in 1888, he refused to treat time as a mere abstract datum and preferred the notion of duration, an inner and lived experience of the passing of time.
Bergson also contrasted intelligence, which is directed towards the creation of tools but is incapable of grasping the movement of life, with instinct, which is an innate and direct knowledge of living matter. Intuition, for him, would be a survival of this instinct in humans, capable of reaching the essence of things where mere intelligence fails.
This philosophy, which he further develops in "Matter and Memory" in 1896, shows that the question of consciousness does not belong solely to laboratories. It remains, even today, a crossroads where the anatomy of the brain, intimate experience of time, and philosophical reflection meet, much like in the time when Leonardo da Vinci and Ambroise Paré were among the first to look inside the human skull.
Author Audrey on 16 January 2023
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