Edouard Machery doesn’t believe that thought experiments have any place in philosophy. That’s about the hottest hot take you can make in philosophy. The ground of philosophy is positively littered with thought experiments. Some of those are thousands of years old and others are quite recent. Machery does have the credentials to make the claim. He is a philosopher of science at the University of Pittsburgh. I don’t have anywhere near the credentials, but I want to defend other philosophers and explain why I think he’s wrong.
At its simplest, a thought experiment is an experiment carried out in the imagination. In philosophy, that usually takes the form of setting up a scenario and reasoning through the consequences. They often rely on intuition, or what Machery calls common sense. They are usually associated with philosophy, especially what’s known as armchair philosophy, but they are used in other fields as well. The sciences frequently use thought experiments. Schrödinger’s cat is a prime example.
Basically, Machery thinks thought experiments are bad because they are not objective. People’s intuitions are different depending on things like gender, class, ethnicity, age, and country of origin. Because they are changeable, they are not objective, they don’t prove anything. But Machery is missing the point of most thought experiments. Machery seems to be a fan of experimental philosophy. This is philosophy that uses empirical evidence in its reasoning. That’s all well and good, but many philosophical questions do not lend themselves to collecting empirical data.
Sometimes thought experiments are used to spur questions. Other times, they are meant to show that something that seems simple is not cut and dry. There are times when they are trying to prove something, but not in the way Machery thinks. They aren’t trying to prove that something is the case. They are trying to prove that something is conceptually or logically possible.
Mary’s Room is a prime example of the first kind. In this thought experiment we are asked to imagine a woman named Mary. She has been in a room without the color red all of her life. So, she has never experienced the color. She has, though, studied color theory, the wavelengths of light, and all that. She knows theoretically all about red. Then, she leaves the room and sees red for the first time. The question is, did she learn something.
If a tree falls in a forest is an example of the second kind. I think everyone is familiar with it. I’ve even written about it before. A tree falls in a forest, and no one is around to hear it. Does it make a sound? This seems like a simple question, but it gets more and more perplexing the more you think about it. There is no objective answer. It is unproveable either way because the only way to prove it is to be around to hear, and that’s expressly forbidden by the thought experiment.
An example of the third kind is the Chinese Room. In this one, we are supposed to imagine a room with a person in it. This person does not know Chinese. People put messages written in Chinese in the room. The person then uses a key to find the proper response, again written in Chinese, and gives it to the person who delivered the original message. This proves that you don’t need to know something (Chinese) in order to spit out coherent outputs. The most common application of the Chinese Room is when thinking about artificial intelligence. It proves the possibility that computers can translate things, do math, play chess, etc. without knowing anything about those activities. It’s still an open question whether sophisticated AIs know anything or will know anything. All we learned from the thought experiment is that it’s possible they don’t.
Machery spends a good amount of time talking about trolley problems. Admittedly, I don’t like trolley problems myself. But that doesn’t mean we can’t learn something from them. I’d classify them as the second type of thought experiment. In the basic trolley problem, imagine there’s an out-of-control trolley. It’s heading towards five workers working on the track. You are near a switch that can move the trolley to a different track. However, there is one worker that will be killed on that track. What do you do? Machery is correct that different people have different intuitions about the right answer. One example he gives is that Gen-Xers are much more likely to pull the switch than Baby Boomers. But, as I said before, Machery is missing the point. The point is that different people would behave differently. Something that seems simple, is it better to kill one person to save five, is actually quite complex.
He also spends time talking about Gettier problems. They are called that because Gettier is the name of the philosopher who came up with them. The case Machery talks about is when a person sees a clock that says 3:00. It is 3:00. The person now knows that it is 3. She has a justified true belief. The catch is that the clock is broken and always says 3:00. It doesn’t prove anything, but it’s not supposed to. It raises questions about the justified part of justified true belief and that’s enough.
In other words, I completely disagree with Machery. The reason thought experiments are so common is because they are useful. They just aren’t useful in the objective, scientific sense. It’s important to remember that science isn’t everything. Two of the points of philosophy are to raise questions and to work out concepts. Thought experiments help us do that.