Definition

An imaginary scenario where a hypothesis, principle, or theory is examined to understand the outcomes.

Why Use It

Folks utilize this concept in science, philosophy, and other disciplines. It generates new information by restructuring and reordering data from a new perspective.

Thought experiments:

• Validate an existing theory
• Question an existing theory
• Create a new theory
• Refute a current theory and create a new one

They communicate complex theories accessibly, spark ideas, and promote speculation. The hypothetical situations and the process of discovery are designed to predict consequences more dependably. The exercise helps folks think outside the box and face hard questions.

When to Use It

Narratives are often an easier route to understanding a hard problem and thought experiments capitalize on this by using analogy to drive comprehension. Someone without previous experience in an industry can quickly learn a challenging idea and connect it to what they know.

One of the earliest examples is Plato’s allegory of the cave where a group of people has lived chained to and facing a blank wall. All they know is the wall and the shadows projected on its surface from fire lit behind them. To them, this wall is the world, and they require nothing else. Unchained, they wander out of the cave to discover the real world.

In the story, a philosopher is considered a sort of prisoner who, upon release, realizes the shadows on the blank wall are not the real world. They aim to see what others have not yet seen and get closer to reality.

How to Use It

A thought experiment can help folks form a hypothesis, and while some questions can be tested, others cannot.

An example of an untested hypothesis is Schrödinger’s cat which sought to make quantum mechanics palatable to the layman. A cat, a flask of poison, and a radioactive source are sealed in a box in the thought experiment. A Geiger counter monitors radioactivity, which, if detected, would shatter the flask and release the poison that kills the cat. Without knowing the outcome, the cat is both alive and dead in the sealed box in this scenario. Once the box is opened, and the external world observes the cat, “superposition” collapses into a specific state of alive or dead.

The experiment illustrates how a quantum system (an atom or photon) can exist in multiple states at once and at what point reality settles on a condition. Schrödinger himself meant to use this idea to illustrate the absurdity of a cat, both alive and dead. Still, like any excellent thought experiment, it has driven the conversation in both directions and remains a part of today’s debate.

A thought experiment starts with a set of hypotheses:

• What might happen if…
• What might have happened if…

And several frames exist:

• Prefactual: Potential future outcomes, given the present. Ex. What will ‘A’ cause to happen?
• Counterfactual: Potential outcomes of a different past. If ‘A’ happened instead of ‘B’, what would be the outcome?
• Semi-factual: How a different past could lead to an identical present. Even though ‘A’ occurred instead of ‘B’, would ‘C’ have still transpired?
• Predictive: Projecting present circumstances into the future. If ‘A’ continues to occur, what will the result be in a specific time range?
• Hindcasting: Testing a hypothesis after an event has occurred to see if the simulation holds up. “A” occurred — did the model predict that outcome correctly?
• Retrodiction: Reverse engineer why events occurred by going back in time until arriving at the root cause. What caused ‘A’ to happen, and how can it be avoided in the future?
• Backcasting: Defining a specific future scenario and going back in time methodically to reveal how it can be achieved. If ‘A’ occurred in the future, what would need to happen to be true.

These frames can be used to:

• Predict or project an unknowable future
• Explain past events
• Aid decision making
• Question the status quo
• Move questions into a new problem space
• Repeat past success
• Discover causation

Thought experiments are flexible and practical in so many situations, including but not limited to the above.

How to Misuse It

The concept is used to spark conversation and ideas around a given question and is not a replacement for experimentation and actual results.

Next Step

Explore a hypothetical question, check your assumptions, and evaluate the consequences. Start by identifying some of the most pressing questions you have and then apply the frame that will be most beneficial for your experiment.

Where it Came From

Thought experiments have been used in philosophy since antiquity, pre-dating Socrates. Folks like Galileo used them in science during the 17th century. Famously, Einstein used thought experiments to discover special relativity. The term Gedankenexperiment, thought experiment in German, was coined by Hans Christian Ørsted.