by Carl Pierer
“Yes, I would let the five people die.”
To philosophers, and I mean to include all people interested in philosophical questions, this is a pretty standard response to a pretty well-known thought experiment: The Trolley Problem. But it is not only in philosophy that you get very uncanny scenarios when trying to clarify an idea by applying it theoretically. These thought experiments play an important role in fields as diverse as physics and arts, mathematics and literature, but the most infamous ones are probably to be found in philosophy, and in ethics particularly. Not only are they notorious, but in fact they face two challenges, which easily turn into dangers should we ignore them and base our argument on them.
First of all, thought experiments have to be distinguished from metaphors, since they serve different purposes. At first sight it might seem that they are poles apart. However, Dennett writes: “If you look at the history of philosophy, you see that all the great and influential stuff has been technically full of holes but utterly memorable and vivid. They are (…) lovely thought experiments. Like Plato's cave, and Descartes's evil demon, and Hobbes' vision of the state of nature and the social contract, and even Kant's idea of the categorical imperative.” Dennett here conflates a variety of famous philosophical scenarios under the heading “thought experiments”. Yet the structure of Plato's cave is completely different from Descartes's evil demon. In Plato's case there is no new knowledge gained. It is not a hypothetical scenario of how the world might be, but rather a more literary expression of how it actually is. The philosopher's ascent from the cave is figurative and an it does not serve the purpose of drawing some conclusion from this view, but rather to embrace the general idea that this is the philosophers' condition. It is a picture, an illustration of his idea rather than a method to develop a new belief. Descartes, on the other hand, imagines an evil demon who brings about a very sophisticated illusion of reality, making us think that all our experiences are real while they are merely his creations. It is an application of radical scepticism. Once we hypothetically accept this scenario Descartes asks whether any of our pre-demonic knowledge still stands. The difference between Plato's cave and Descartes's demon is that the former is a mere illustration of an idea. The latter, in contrast, serves to provide some new insight. Therefore, I propose to distinguish between thought experiments and metaphors. The purpose of the former has to be a more rigid one than that of the latter. We use thought experiments to test what happens if we apply our theoretical ideas. Its similarity to actual experiments should not be ignored. We peruse those hypothetical results, and only if we can accept them are we ready to accept a theory.
However, more often than not, thought experiments are used the other way round. Hypothetical scenarios are invented in such a way that our theories fail to deliver what is expected of them.