Understanding Metaphysics: Descartes’s Ghost in the Machine

From a lecture series presented by The Great Courses

Thanks to the Enlightenment and scientific advances over the past 300 years, our understanding of reality has been redefined. But when we talk about redefining reality, we are presuming first that there is a reality and that it’s something we define. Philosophers since the 1700s have been fascinated by this question of knowing reality. It is what philosophers call metaphysics, and Rene Descartes was the godfather of this powerful field of study.

metaphysics concept

Sadly, we often associate the word metaphysics with occult beliefs like ESP or telekinesis, but what it really means is the study of reality itself. What exists—that is, to borrow a phrase from Isaac Newton—what is the “furniture of the universe”? What are its properties, and what are the relations among these various elements? That is what metaphysics is about, and Descartes provided a foundational method for studying these questions.

The Father of Modern Philosophy

Rene Descartes
Rene Descartes (1596-1650) was the godfather of modern philosophy.

Rene Descartes was known as the father of modern philosophy, as well as the father of analytic geometry, and the framer of our first modern theory of gravitation—a generation before Newton. Descartes began his entire intellectual odyssey with this question: How do we know there is a reality outside our own mind? We know that we have experiences—we see things, hear things, smell, taste, and touch things. Each of us can be sure of our own experiences, having experienced them, and, therefore, you can be sure that you exist. This logic is the basis of Descartes’s famous dictum, “I think, therefore I am,” meaning that my thoughts prove that there must be at least one thing in the universe: the thing thinking my thoughts—that is, me.

Learn more about the best way to gain knowledge

But—and here’s the big question—how do we know that the internal experiences we have correspond to objects outside our minds? I can look at a loaf of bread. I can smell it fresh out of the oven. I can touch it and hear the crunch of the crust when I poke it. I can taste it. But where is this vision, this feeling, this hearing, this tasting? Not out in the world, but in my mind. How then do I even know that there is a world out there, and if there is, how do I know that it resembles the world of my internal experiences? If all my experiences are in my mind, how do I know that the thing giving me the bread-type experiences is, in fact, bread?

This is a transcript from the video series Redefining Reality: The Intellectual Implications of Modern Science. Watch it now, on Wondrium.

Perhaps, Descartes considers, “I am dreaming or there is an evil demon”—or in modern terms, a supercomputer—feeding my experiences into my mind, creating a false universe with bread that I wrongly believe is real. Descartes—and everyone else—ultimately rejects this hypothesis, in part because there are surprising regularities in our experiences that are beyond our ability to control or create. When we keep careful track of our observations, surprisingly intricate patterns emerge that can be generalized to systems we had never previously known or imagined.

What do we call the study of these patterns of observations? Science. We take these patterns and we create theories to explain their appearance.

These theories, in turn, posit mechanisms which are supposed to be in the world and responsible for creating the patterns. But we can use these theories not only to explain what we have already seen—more excitingly, we can use them to predict new observations we have yet to make. If these predictions come true, we take it as evidence that the mechanism in the theory is likely an actual part of the real world. In this way, we use our best scientific theories to define reality and then redefine it as new theories emerge, each time giving us a new picture of what there really is, and how it works. When we have new theories replace old ones, we not only gain new understandings about how observations relate to each other, but we conceive of the entire world itself in new and strange ways.

Learn more about the modern intellectual tradition from Descartes to Derrida

The Intersection of Science and Philosophy

Scientists give us the new accounts of how the universe works and philosophers then unpack those theories to see what they tell us about what is real. Descartes’s thought experiment in which our experiences are fed into our minds by an evil demon is now called the “Brain in a Vat” problem—that is, how do we know we are the people we think we are, living the lives we think we’re living, and not just brains in vats being lied to by a computer?

You might recognize this as the plot of a popular movie from the 1990s: The Matrix. As the movie serves as a dramatization of the metaphysical work of Rene Descartes, the point is that science gives us pictures of reality, and those pictures then show up in art, film, literature, music, and even architecture.

Sometimes the cause and effect relation is in the other direction. Scientists may also look to the world of arts and letters for new and imaginative ideas to create the lenses which they will then use to envision the world in new and exciting ways. Sometimes the fictional worlds of the artist change how scientists tell us the world really is. What we will do is look at the ways we were forced to re-understand reality in the face of science in the 20th and 21st centuries, and how those new perspectives relate to our other intellectual endeavors.

One example is how we think of the human body. According to Descartes, we are made up of two parts: body and mind. The body is mechanical and runs according to the laws of physics. The mind is nonmaterial and where the will resides. At the time, the concepts of mind and soul were the same. Descartes’s theological commitments required that only humans are a combination of body and mind, because only humans have souls.

This view was ridiculed in the early 20th century by Oxford philosopher Gilbert Ryle, who called it Descartes’s “Ghost in the Machine” view, where the immaterial and immortal soul is the ghost part, and the perishable, physical body is the machine. Far from science and religion being opposed to each other, the metaphysical view attached to our best scientific theories at the time was explicitly tied to a religious picture of reality. But this concept of human body as machine is not just a philosophical or theological construct; it long formed the basis for our view of ourselves. For centuries, medical science was based entirely on this picture, and challenging it in any way was difficult—even by well-respected medical researchers with the strongest evidence.

Learn more about foundationalism and Descartes’s evil demon

Toward a New Understanding of the Body

 Ignaz Semmelweis
Dr. Ignaz Semmelweis (1818-1865) was schooled in the theory of a human as a ghost in the machine. As a result, he was initially convinced that any problem with the body meant that a part of the machine was malfunctioning.

Ignaz Semmelweis was an Austrian doctor working at the first maternity ward in Vienna General Hospital in the 1840s. At the time, childbirth was a dangerous matter and women frequently died from a number of different causes while giving birth. One of these was childbed, or puerperal fever: an illness that caused fever, terrible pain, and ultimately shut down the body’s organs, leading to a prolonged and horrible death. While this condition affected mothers everywhere, Semmelweis noted that it was rampant in his ward. Not just at his hospital, where about 2 out of every 100 women contracted it, but in his ward, where anywhere from 8 to 12 women out of 100 would die from it. A 600 percent increase in a terrible disease: that’s not something a doctor could ignore—especially when the incidence rates were even lower in mothers who gave birth away from the hospital, and even among those who gave birth in the street en route to the hospital. The Hippocratic oath tells doctors that they should do no harm, and yet it seemed here that’s exactly what was happening. What was causing it, and how could it be changed?

Semmelweis was schooled in the theory of a human as a ghost in the machine. As a result, he was initially convinced that any problem with the body meant that a part of the machine was malfunctioning, but which part? Semmelweis tried one hypothesis after another. He considered diet. He considered having the women lie on their sides instead of on their backs during childbirth. No mechanical change altered the rate of contagion. But when a colleague—another surgeon—died after a medical student accidentally stabbed him with a scalpel used in an autopsy, Semmelweis considered the possibility that the doctors themselves were a vehicle for the ailment.

Semmelweis’s was a teaching ward, and the doctors would frequently go straight to the birthing room from the dissection table—where they were showing students the parts of the machine, using cadavers as models. For such doctors, dirty smocks and dirty hands were a sign of hard work; the dirtier you were, the more industrious you were being. Childbirth was hardly a clean endeavor; thus, the thought of cleaning up before getting dirtier just seemed absurd.

But Semmelweis demanded that his people would clean up, and wash their hands with a chlorine solution before assisting with a birth. Cases of childbed fever then fell to the same incidence rates seen everywhere else. Semmelweis had found the cause of the illness: It turned out to be a type of bacteria, present in both dead and infected tissue. A new model for human reality was beginning to emerge.

From the lecture series Redefining Reality: The Intellectual Implications of Modern Science, taught by Professor Steven Gimbel

Images courtesy of:
Jenő Doby [Public domain] via Wikimedia commons