There is a dichotomy between material objects and ideas. They are fundamentally different from each other, yet there seems to be an interaction between them. How is that possible? An object has physical properties, an idea doesn’t. So, how can there be an interaction between them? Let’s take a look.
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Descartes’ Flawed Anatomical Solution
René Descartes tried to solve this problem anatomically. He knew that the brain was the bodily organ responsible for action, so the mechanism by which the mind interacted with the world must reside there. He also knew that there’s a network of nerves through the body that are in part responsible for taking data about the interaction of the world and the body back to the brain, where they somehow gave rise to observation and were also responsible for the movement of muscles by the mind.
So, he figured that these nerves would be tubes, much like the veins and arteries also crisscrossing the body.
When veins and arteries carry blood pumped by the heart, these nerve tubes would carry a different fluid: animal spirits—that is, spirits in the sense of a liquid, not spirit in the sense of a soul; although for Descartes, soul, mind, and spirit would have the same sense. It’s through disturbances in the flow of the animal spirits that the mind would receive news of the physical world, sending out its commands to the body.
According to Descartes’ hypothesis, the part of the brain responsible for this is the pineal gland, a small part of the brain that had the twin virtues of being centrally located and Descartes not having any idea what else it might be doing. It’s through the manipulation of the animal spirits by the pineal gland that the mind connects with the body, that we have the interaction between these two distinct parts of reality.
It turns out, of course, that this theory fails. We know that the nerves don’t carry a subtle fluid and that the pineal gland is responsible for producing melatonin, a hormone that plays a crucial role in sleep and our bodily rhythms. But the central metaphysical question is still with us; is there a single sort of thing, in reality, just material, or is there some other sort of entity?
For Descartes, this other sort of entity was a soul and particular to humans. Animals, he thought for theological reasons, cannot have minds or souls. Clearly, Descartes did not have pets.
Over time, the theology was weaned from the dualist view and living things were simply held to possess what the French philosopher Henri Bergson called an élan vital—a vital force or vital impulse; what the German thinker, Arthur Schopenhauer called the “will to be”.
Living things have a will that non-living things do not. It’s this will, this power to desire and cause to happen through internal means that separates the living in the universe from the non-living.
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The Materialist and Dualist View of the Brain States and the Mind States
The brain is relevant here; it’s necessary, but it’s not sufficient. We can take a CAT scan and see that when we have certain kinds of thoughts, a certain area of the brain is active. When we have a certain sort of desire, a different section is engaged. When we have a certain sort of sensory experience, a completely different region lights up.
We can conclude that there’s a correlation between the state of the brain and human experience, but the dualist will say that this correlation is a relation between two different things.
The materialist, someone who denies dualism, someone who contends that there’s only one sort of metaphysical entity and that reality is strictly and solely material, must hold that brain states and mental states are the same things—that they’re different descriptions of the same occurrence.
The dualist, on the other hand, holds that brain states and mental states are fundamentally different. We can point to the spot in the brain that’s active when I feel the pain in my stubbed toe, but the pain I feel—the experience of pain—is not the same thing as the neural activity.
The two are linked, but they’re different according to the dualist. They are the same according to the materialist, but consciousness for the dualist is completely different, it’s non-material.
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Human Consciousness in the Quantum System
One physicist who made this case was Eugene Wigner. He was concerned with what we’ve seen in quantum mechanics as the measurement problem. Recall that the equation governing the development of quantum systems is the Schrödinger equation.
When a quantum system is not observed, it occupies a state of superposition, that is, it’s in a combination of every possible state it could occupy. The Schrödinger equation describes how this superposition develops according to the potential energy in the environment of the system.
But the instant we observe the system, it fails to be in this superposed state; but instead, appears in one and only one of the possible states. We can never predict which one it will be—the Schrödinger equation gives us the odds that we’ll find it in each of the possibilities, but the best we get is this probability. The problem here is that we have a physical law in the Schrödinger equation that always holds, except when we look.
Physicists were bothered by three aspects: One, how can you have a universal law of the universe that can be violated? Two, why is the violation subject to randomness? This was Einstein’s problem. And three, what is it about us looking at something that causes the violation? It’s this third question that Eugene Wigner tried to answer.
One interesting thing about quantum systems is that they become entangled—we talked about this earlier for the identity of particles. If two electrons bounce off one another, we may be able to label them as Bob and Carol coming in, but we can’t say which one is Bob and which one is Carol coming out; the best we could do is to say one is now Ted and one is now Alice.
The two electrons cease to be independent things in the world that subsist and persist, but rather are just disturbances of a particular sort in the underlying field. When we talk about the behavior of the field, the reality of things themselves is lost. We say, in this way, that the parts of the system have become entangled and we can only describe the system as a whole.
This is a transcript from the video series Redefining Reality: The Intellectual Implications of Modern Science. Watch it now, on The Great Courses Plus.
The Experiment Called Schrödinger’s Cat
This is what makes the thought experiment called Schrödinger’s cat so troubling. The idea is that we can easily create what are called spin-correlated particles. Electrons, for example, have a property called spin—not that little ping pong balls are spinning, but the effect is much like what physicists recognize in the angular momentum of a rotating charged object.
A thing can be said to spin clockwise or counterclockwise and there are different effects for each. We can create pairs of electrons such that when we don’t look at them, both are in superposed states of clockwise and counterclockwise. But as soon as we observe one, both collapse into a single state of clockwise or counterclockwise such that one is always the opposite of the other. But we never know which will be which—it’s equivalent to a quantum coin flip.
So, attach the apparatus that creates these pairs to a spin detector that will observe the spin of one of these particles. Attach the detector to a circuit connected to a poison gas canister such that if the detected particle is spinning clockwise, the circuit does nothing. If the detected particle is spinning counterclockwise, the canister is opened, allowing the gas to escape. Finally, place the canister in a closed box containing a cat.
We push the button, a correlated pair of electrons is emitted, and the detector determines the spin of one. If the electron collapses from its superposed state into a clockwise spin, nothing happens and the cat lives. If the electron collapses from its superposed state into the counterclockwise spin state, then the detector sends the signal through the circuit, the gas escapes, and the cat dies.
But suppose we push the button and don’t look in the box? The detector’s made up of atoms—it’s a physical thing subject to the laws of quantum mechanics. If we have not observed the detector, its atoms will be in their superposed state, which is now entangled with that of the emitted electron.
The circuit likewise, just more atoms which are unobserved. And so they obey Schrödinger’s equation in a way that has them entangled with the state of the larger system. And it’s with the canister of gas and the cat—assuming a picture of the cat-like that of Descartes, in which the cat has no mind capable of making an observation.
All of these are just atoms, all of these unobserved, and therefore all of these in superposed states in a grand entangled system. When we don’t observe the system, it’s in one big superposed state—meaning that the cat is in the superposed state of being alive and dead. It is not half-dead, it is not in the process of dying, but rather it’s in the superposed state of being both alive and dead.
But the instant we open the door to look inside at the cage, we see either a dead or alive cat. The wave function collapses into just one state.
But wait a minute, we are just atoms too, right? We too should be part of the system, as should the rest of the universe. There should be no collapsing from the superposed state into a single property state. Schrödinger’s equation should always be inviolate. Where is the only place in the process that a different sort of entity could be active?
Wigner concluded that the only place is in the making of the observation—an observation is when we learn of the result when our consciousness becomes involved. Other than our consciousness, there’s nothing but atoms here and nothing that should affect the system to cause the collapse.
It’s only our consciousness—or perhaps that of the cat—which we can find as fundamentally different here. Maybe, like Descartes, we need to hold that there is matter and there is mind and the two are completely different, but they interact.
If this were true, it would allow us to make sense of one of the most troubling aspects of quantum theory. But what sense do we then make of a non-material consciousness? And how does it cause the collapse of the wave function? It may answer one question, but it raises several others.
Common Questions about Quantum Consciousness
Rene Descartes hypothesized that the pineal gland in the brain manipulated something he called animal spirits (spirits in the sense of a liquid, not spirit in the sense of a soul), which enabled the mind to connect with the body, enabled the mind to receive news of the physical world, and send out its commands to the body. We know now that the theory fails, but this is what Descartes believed.
Even though Rene Descartes identified that humans were more than just the physical body and brain, that there existed another entity called soul, for him this was restricted to humans. Animals, he thought for theological reasons, cannot have minds or souls. This theological point of view eventually weaned from the dualist view and living things were simply held to possess what the French philosopher Henri Bergson called an élan vital—a vital force or vital impulse.
According to theoretical physicists and mathematician Eugene Wigner, the only place in a quantum system where a different sort of entity could be active is in the making of the observation. Observation is when we learn of the result when our consciousness becomes involved. Other than our consciousness, there’s nothing but atoms in the quantum system and nothing that should affect the system to cause the collapse. So, the wave function collapses into just one state directly because of the introduction of human consciousness in the system.
The theory of dualism contends that brain states and mental states are fundamentally different, but the two are linked. Also, consciousness in the realm of dualism is completely different, it’s non-material.