Thought Experiment
Use your imagination to explore what cannot be tested in reality
Thought experiments are devices of the imagination used to investigate the nature of things. They let us do things in our heads that we cannot do in real life, exploring situations from more angles than we can physically examine and test for. They help us learn from mistakes before making them, evaluate potential consequences, take on the impossible, and reexamine history to make better decisions.
To be useful, thought experiments require the same rigor as traditional experiments: ask a question, conduct background research, construct a hypothesis, test with mental experiments, analyze outcomes, and compare to the hypothesis. Their chief power lies in removing constraints. When we say 'if money were no object' or 'if you had all the time in the world,' we are asking someone to conduct a thought experiment by removing a variable that is physically impossible to remove. This leads to insights about what we truly value.
Thought experiments serve three major functions: imagining physical impossibilities (as Einstein did with his elevator thought experiment that led to general relativity), reimagining history through counterfactuals (exploring what might have happened if key events unfolded differently), and intuiting the nonintuitive (as John Rawls did with his 'veil of ignorance' to reason about just social structures). The key caution is that history is a chaotic system where small changes in initial conditions can produce vastly different outcomes.
- Thought experiments let us explore situations from more angles than physical testing allows.
- They require the same rigor as real experiments: hypothesis, testing, analysis, and adjustment.
- There is no limit to the number of times you can change a variable to see if it influences the outcome.
- History is a chaotic system; small changes in initial conditions can produce vastly different outcomes.
- The events that happened are but one realization of the historical process among many possible outcomes.
- Ask a clear questionDefine precisely what you want to explore. Frame it as a specific, testable question rather than a vague wondering. The sharper the question, the more useful the thought experiment.Pro tipRefine your question as you go. Start broad, then narrow to the most important variable.
- Conduct background researchGather the information needed to make your mental simulation realistic. Understand the context, constraints, relationships, and dynamics at play in the scenario you're exploring.Pro tipThe more accurately you understand the real-world context, the more valuable your thought experiment will be.
- Construct your hypothesisBased on your research, form a clear prediction about what would happen under the conditions you're imagining. Make it specific enough to be tested mentally.Pro tipConsider multiple competing hypotheses rather than anchoring on one.
- Run the mental simulationImagine the scenario playing out in detail. Change variables one at a time to see how they influence the outcome. Run it hundreds or thousands of times mentally to see the full spectrum of possible outcomes.Pro tipFor the LeBron vs. Woody Allen basketball question, out of a hundred thousand game scenarios, Allen probably wins only in the few where LeBron breaks an ankle at the start.WarningBe cautious with historical counterfactuals. History is chaotic; you can easily mislead yourself by assuming small changes would produce predictable results.
- Analyze and draw conclusionsCompare the results of your mental simulation to your hypothesis. What did you learn about the limits of what you know? How did changing variables affect outcomes? What does this tell you about where to focus your energy?Pro tipThis process makes you aware of your decision-making process, so even when results are good, you can recognize when it was luck versus skill.
Einstein imagined a person in a closed elevator, feet glued to the floor, with no external information. Would they be able to tell whether the elevator was in outer space being pulled upward at an accelerating rate, or sitting on Earth being pulled down by gravity? He concluded they would not, because the forces are identical.
Buffett asks people to imagine a genie appearing twenty-four hours before their birth, offering them the chance to design all the rules of society. The catch: they don't know whether they'll be born rich or poor, male or female, in the United States or Afghanistan. They must pick one ball from a barrel.
The book presents a thought experiment about buying $100,000 of Google stock on 50% margin. When the stock doubles, you triple your money and feel like a genius. But running the scenario hundreds of thousands of times reveals that Google could have dropped 50% first, triggering a margin call and leaving you with nothing.
Thought experiments have a long history across multiple disciplines, from philosophy to physics. Albert Einstein was perhaps the most famous practitioner, using thought experiments to develop both special and general relativity. His elevator thought experiment, imagining whether a person in a closed elevator could distinguish between gravity and acceleration, led to the formulation of general relativity.
The trolley problem, first proposed in modern form by philosopher Philippa Foot and extensively explored by Judith Jarvis Thomson, demonstrated how thought experiments could advance moral philosophy without requiring anyone to actually be harmed. Warren Buffett's 'ovarian lottery' thought experiment, asking people to design social rules before knowing what position they would hold in society, draws on John Rawls's 'veil of ignorance' from A Theory of Justice to illuminate questions of fairness and luck.