The philosophy of the mind is a large field in philosophy that discusses what happens in our mind and in our experience. Philosophers in this school of thought construct various thought experiments to describe esoteric ideas and call into question what our experience and thoughts actually mean. This list is obviously a cursory introduction to these thought experiments. If you want more information about them, please make sure you study them.
I tried to get this one on Listverse, but it didn’t work out.
In his time Rene Descartes considered how he could know whether he was just a brain in a vat or whether he was full human being. For years philosophers grappled with the problem up until the 19th century, where physicist Ludwig Boltzmann came up with a similar thought experiment. Boltzmann was a leading figure in thermodynamic research and studied entropy as well as the arrow of time. His thought experiment spans the gap between philosophy and physics.
Our universe seems extremely uniform, especially in a thermodynamic sense. Boltzmann’s brains addressed the paradox. Imagine instead of our universe have a low state of entropy, it instead had an extremely high state of entropy. Random fluctuations in the entropy state would create little pieces of low entropy. Among the random fluctuations are self-aware entities that just exist in thinking states. These are the Boltzmann brains. If these entities did exist, they would be unable to formulate any conclusive arguments, since anything that popped in their minds would just be random low-entropy fluctuations.
The immediate outcome of believing that it is much more likely that the universe of high entropy, any low entropy fluctuations like his brains would be simple in form. They would not need a body of any type, just disembodied intelligence. What is really weird is that Boltzmann’s line of reason tells us that our universe should be filled mostly with these disembodied brains, since they are the most basic form of intelligence and the one that the universe would select for. However, Boltzmann is not stating that this is how our universe actually is. It is actually a reductio ad absurdum argument, showing that the line of thinking of our universe as a low-entropy fluctuation from a higher entropy universe is absurd. Modern physics tells us that Boltzmann brain entities are highly unlikely, but it remains an interesting idea.
When you see somebody walking on the street how can you tell that person is conscious? Our immediate answer to that question is to propose a series of tests. We can talk to them and see if they respond. We can kick them and see if they respond to pain. We can do all sorts of different things. But in the philosophy of the mind the concept of a philosophical zombie (usually shortened to p-zombie) overturns our normal conceptions of conscious and the mind. A p-zombie is hypothetical creature that is perfectly designed to mimic consciousness without actually experiencing it. P-zombies are perfect copies of humans.
If you saw a p-zombie on the street, you would be able to interact with it and believe that it was a living, sentient human. It would interact with the world perfectly. At first thought it seems absurd to have this sort of creature, since we are unable to think of human-like life without sentience. But if such a creature did exist, it is impossible to decide whether they experience consciousness like the rest of us.
Philosophers use the idea of a p-zombie to refute certain schools of thought, mainly physicalism, which is the idea that consciousness comes from the material structure of a person. A physicalist argues that consciousness is an emergent trait from the way that our physical bodies. But p-zombies propose a counter-point to that point of view. We can imagine a p-zombie with all the same physical characteristics as a human, but they do not have consciousness like we do. Some philosophers argue that the mere fact that we can imagine such a being shows that physicalism is not true, since our brains can think outside physicalist philosophy. If the physicalists were right, some argue, our brain would not have the structure and ability to think outside of itself and imagine a p-zombie. Still, the debate rages on.
Another thought experiment that challenges physicalist ideas is the China Brain experiment. Imagine that we had the nation of China get together. We would ask each citizen to simulate one neuron in the human brain. By using standard communication means, each of the “neurons” would send information across the Chinese population. In our thought experiment we would assume that this setup perfectly mimics the human brain.
With the nation of China acting as a single brain, we can now ask whether the Chinese nation is conscious. They are simulating all the effects of the human brain perfect. In the physicalist school of though known as functionalism, the China Brain is a conscious entity. It has all the characteristics of consciousness and thus we can consider it as sentient. A functionalist would also argue that consciousness does not have just one definition, rather anything that functions as a consciousness is one, including the Chinese Brain.
Of course this is a controversial point of view. Other philosophers argue that the Chinese Brain is obviously not conscious. Even though it functions like a human brain, it does not have the qualia, or individual subjective experiences necessary for consciousness. Interestingly, this thought experiment has implications for artificial intelligence. Since a machine brain is just manufactured components put together, it is similar to the Chinese Brain. For an AI, does the different machine parts put together create an emergent consciousness, or is their something else that makes consciousness that nobody can manufacture? As AI gets closer, these are questions that will have bearing on our future.
While consciousness is a big area of argument in the philosophy of the mind, another interesting area is the idea of subjective experience, or qualia. Philosophers have long wondered whether it is possible to compare the qualia between two minds and figure out reality. To explain this difficulty, philosopher Daniel Dennett invented the brainstorm machine thought experiment.
For this experiment we imagine a machine that can transfer experiences across two people. When plugged up to it, you experience exactly the same experiences as the other person hooked up to the machine. Imagine that during this brain transfer, a philosopher asked you to describe exactly what you saw. For most of the time, you can effectively describe what the other person is experiencing, with one minor difference. The colors are all wrong. The sky is yellow, grass is red, etc. Mentioning this fact to the technician, he realizes that one plug got turned upside down during set up, and promptly corrects it, giving you the “normal” colors.
But which experience is right? If such a machine existed, there is no possible way for the designers to know exactly what experience to calibrate the machine to. Every person experiences different qualia. Thus any sort of comparison between two minds is impossible. All of us are experiencing different things in our minds, and we are all correct. Even more interesting is the idea that we can not actually discover if our qualia is correct through introspection. The blue that we think of as the sky might be a totally different color to another person, but nobody can know that they are experiencing proper qualia that represents reality.
While most people associate the word swampman with some sort of bizarre cryptid hanging around wetlands, the Swampman in this list is a philosophical thought experiment that looks to challenge what it actually means to have a mind. Proposed by Donald Davidson, for this thought experiment we imagine Davidson walking through a swamp. Suddenly lightning strikes, killing Davidson. At exactly the same time another bolt of lightning strikes the swamp and creates a new creature that has the same molecular and physical structure as Davidson.
Is this swampman Davidson, or are they actually unique beings? The swampman can interact with all of Davidson’s friends and family, but he can not recognize them because he was never met them before. Davidson pointed out that this swampman would have no history. Even though he was structurally the same as Davidson, the swampman never experienced anything from Davidson’s life and thus is not the same person. In essence, the difference between Davidson and the swampman comes down to one having experienced Davidson’s life and the other emerging from a lightning bolt.
Of course, other philosophers have argued against Davidson’s ideas. They state that considering the swampman as a distinct person is faulty since it relies on something intangible to define the person. Practioners of the mind-body theorem state that since the swampman has a brain structural indistinguishable from Davidson’s, it has a mind just like Davidson does. Other philosophers argue that the what makes the swampman unique is the choices that the two beings make. They are indistinguishable until each acts on a decision, at which point their separate consciousness emerges.
Imagine a brilliant scientist named Mary stuck in a room. Her room is black and white and she only interacts with the outside world through a black and white television monitor. Through her observations Mary learns everything to know about color. She learns to identity certain objects with color. For example, that the sky is blue. But she has never actually experienced color. Now suppose that Mary leaves the room after a while and looks at the color world. Even though she knows everything to know about color, does she learn anything new by observing the world?
This question has large implications in the philosophy of mind. When asked if Mary learns something new, most people will answer that she does, since experience matters. If we say that Mary does learn something new by directly observing the outside world, then that proves qualia, or discrete subjective experiences, exist.
Beyond that, the knowledge argument refutes the ideas of physicalism. Since most people would assume that Mary learns something new, that shows that something exists beyond the physical states of the mind. Mary’s brain did not change in any physical way, but she still learned something new from her experience from the outside world.
Not all philosophers are content with that idea. Some argue that Mary has not learned anything new, but rather has gained a new ability, the ability to directly see the colors that she is studying. Thus the experience did matter, but it did not change anything about her color knowledge, it just gave her new avenues to explore the color world.
Twin Earth Thought Experiment
Hilary Putnam proposed one of the most interesting thought experiments in the philosophy of the mind. Proposed in 1973, the Twin Earth Thought Experiment deals with meaning in the mind, a similar idea to Wittgenstein’s beetle. Putnam proposed that we could imagine a Twin Earth, where there is twin of everything we see on our Earth, down to the most minute details. There is only one difference. Twin Earth does not have water.
Instead of water, Twin Earth has a chemical that is superficially similar to water but chemically different. Putnam called this chemical XYZ. But, this chemically is so superficially similar to water that it is impossible to tell the difference. In fact, the Twin Earth dwellers have named their XYZ chemical water as well. Putnam proposed the following question: If two people from each planet met up and talked about water, would they be talking about the same thing?
Putnam stated that the chemicals are different no matter the name given to them. Thus, we can not rely on what we have in our brains to give correct meaning to words. Instead, people need to look outside of their brains to figure out what words mean, and that involves looking through the causal connections between words. It is critical to understand how words and ideas came about since we can not rely on what the contents of our own minds. The external world is critical in figuring out what things mean.
Out of all these thought experiments, the one that has the most influence on our future in John Searle’s Chinese Room. Not only is this experiment critical in the philosophy of the mind, it has implications with artificial intelligence. Imagine that you are in a room. Everyday you receive messages in a language that you do not know (Searle used Chinese). In your room you also have a precise set of rules that allows you to get the messages and write responses. For example, if you see one character on the page, you write a certain corresponding character.
Searle imagined that the rules are so good that the messages that you write are not only comprehensible, but a native Chinese speaker would assume that somebody fluent in Chinese wrote the messages. The kicker is that the person in the Chinese room never actually understood what they were writing or receiving. They can function as a transcriber, but they have not actual knowledge of the Chinese language.
This thought experiment hits on the topic of consciousness. For anybody observing the actions of the Chinese room, they would say that it is conscious, even though the transcriber has no conscious understanding of what the messages mean, they are just following a set of rules. By considering the Chinese room, it becomes clear that consciousness might just be a set of rules that our brains play.
There is an obvious connection to artificial intelligence. AI brains execute actions by programs. If one of these brains is as smart as a human is it really conscious? Possibly. But it could also be that the excellently planned series of codes mimic human thought, even though there is no conscious activity occurring in the AI brain.