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3 Famous Thought Experiments, or The Art of Counterfactuals

While “Gedankenexperiment” (literally “thought experiment”) was a term initially coined by the 19th century Danish physicist and chemist Hans Christian Ørsted, many claim that the common mental technique can be traced all the way back to Galileo and before that the ancient Greeks.

But what explains this long and storied history? Why have thought experiments been so valuable to some of history’s greatest minds? And what value do they hold for today’s lifelong learners?

How to Define Thought Experiment

According to the Stanford Encyclopedia of Philosophy, thought experiments are essentially a tool of the imagination used for “entertainment, education, conceptual analysis, exploration, hypothesizing, theory selection, theory implementation, etc.” While academic debates have raged on for years as to the exact parameters, some scholars have defined a thought experience as the ability to generate a mental model of a situation.

For example, the cognitive scientist Nancy Nersessian recently defined the mental strategy as “the construction of a model of a kind of situation [in which] manipulating that model through simulation affords epistemic access to certain features of current representations in a way that manipulating propositional representations using logical rules cannot.”

In other words: our ability to visualize or play out a scenario in our head allows us to discover things about the scenario otherwise unavailable to us through formal logic or abstract reasoning. Fundamentally, it is an approach to learning.

Another slightly more concise definition comes from the philosopher George Schlesinger, who took stock of the technique in his 1995 essay “The Power of Thought Experiments” in order to distill the technique’s true value. “[T]he great usefulness of thought experiments,” he writes, “derives from the remarkable pliability of counterfactuals.”

What Schlesinger is getting at here revolves around what he means by a “counterfactual,” which is just a fancy word for our ability to imagine scenarios contrary to reality. It’s a habit many of us use in our day to day life. Just recall anytime you’ve begun a sentence with “If only…” or “What if…” This kind of self-reflection is what we call a counterfactual, and by extension is a rather simple yet pervasive kind of thought experiment.

Taking this into consideration, we can see what Schlesinger’s getting at when he talks about the “remarkable pliability of counterfactuals.” Namely, that the true value of thought experiments comes from the human ability to play with hypotheticals using our wild imagination.

And it’s this imagination that has made possible some of the greatest discoveries by some of humanity’s greatest minds, including Einstein himself.

In order to truly illustrate how powerful this technique can be, especially for lifelong learners, let’s take a look at some examples. As I hope you’ll see, not only is this technique a crucial skill for those grappling with complex subject matter, but it is also an indispensable habit and learning tool for those looking to strengthen their critical thinking skills.

3 Famous Thought Experiments by Contemporary Thinkers

The list of well-known thought experiments is a long one, but here a few examples that have caught the attention of recent scholars.

1. Mary’s Room Thought Experiment

The philosopher Frank Jackson posed in 1982 the thought experiment most commonly known as Mary’s Room, or Mary the super-scientist. The scenario involves Mary, a scientist living in an entirely black and white world who has detailed, scientifically-accurate descriptions of color and yet no first-hand experience of color. From here, Jackson poses the question: if Mary has complete knowledge of the physical properties of color, will she gain any new knowledge upon exiting the black and white world and observing color herself?

As one might imagine, such a thought experiment highlights the gap between physical description and experiential knowledge. To Jackson, it seems quite plausible that upon exiting the black and white world Mary’s experience of observing color may fall entirely outside her previous wealth of knowledge concerning color and its physical properties, leading us to believe that there is a worthwhile distinction between scientific fact and our experience of those facts.

2. Chinese Room Thought Experiment

Another well-known thought experiment comes from the philosopher John Searle. This hypothetical imagines that we are alone in a room, with someone outside slipping sheets of paper under the door with Chinese characters on them. Because we do not understand Chinese, we follow instructions from a computer program for how to manipulate the symbols, which we then slip back out under the door.

From the perspective of those outside the room, it seems as though we understand Chinese. To us, it seems that we are merely following arbitrary instructions that are completely disconnected from any form of understanding or language fluency.

In this way, Searle’s thought experiment is intended to reveal that computers often use specific rules to manipulate symbols without arriving at any real understanding of grammar, semantics, or meaning themselves. Thus, for Searle, the lesson of the thought experiment is that our tendency to compare the human brain to a computer is misguided given that computers—at least in their current form—are only able to simulate the process of full understanding.

3. Drowning Child Thought Experiment

Our final example comes from the philosopher Peter Singer, who has garnered a reputation for his work on morality and politics. The thought experiment he proposes is a hypothetical he’s presented to many of his students in order to reveal pressing modern day ethical concerns. In his words:

“To challenge my students to think about the ethics of what we owe to people in need, I ask them to imagine that their route to the university takes them past a shallow pond. One morning, I say to them, you notice a child has fallen in and appears to be drowning. To wade in and pull the child out would be easy but it will mean that you get your clothes wet and muddy, and by the time you go home and change you will have missed your first class.

I then ask the students: do you have any obligation to rescue the child? Unanimously, the students say they do. The importance of saving a child so far outweighs the cost of getting one’s clothes muddy and missing a class, that they refuse to consider it any kind of excuse for not saving the child. Does it make a difference, I ask, that there are other people walking past the pond who would equally be able to rescue the child but are not doing so? No, the students reply, the fact that others are not doing what they ought to do is no reason why I should not do what I ought to do.”

From here, Singer emphasizes that such a situation already exists today, particularly from the point of view of wealthier countries where your average citizen enjoys relative peace and affluence, meanwhile exploitation, starvation, and other forms of suffering remain prevalent elsewhere. Thus, the philosopher wants to ask: Why does our behavior not line up with our professed values? What action should we be taking that we aren’t?

As you can see, such thought experiments have been posed in a diverse set of contexts and range widely in their implications—be it in the realm of epistemology, technology, or ethics.

So, next time you’re contemplating something important or diving into some difficult learning material, consider what kind of counterfactuals might help you think more critically about the situation.

By Gabe Kahan for Mission to Learn

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