Thought Experiments

A thought-experiment is a hypothetical scenario set forth as a puzzlement or a basis for argument

Table of Contents

  1. Thought Experiments
  2. Philosophic Thought Experiments
    1. Judith Jarvis Thomson’s Famous Violinist
    2. Derek Parfit’s Split Brain Thought Experiment
    3. Brain in a Vat
    4. Living Neurons Gradually Replaced with Synthetic Facsimiles
    5. John Rawls’ Original Position

Thought Experiments

  • A thought-experiment is a hypothetical scenario set forth as a puzzlement or a basis for argument.
  • A classic example is Einstein’s Falling Elevator Gedankenexperiment, which he said led him to his theory of gravitation.
    • Inside a closed container, there’s no way to tell whether you’re in free fall toward Earth or in zero gravity in intergalactic space

Philosophic Thought Experiments

Judith Jarvis Thomson’s Famous Violinist
  • Judith JarvisThomson was a faculty member at MIT for 40 years, retiring in 2004. She remained active in philosophy at MIT, writing articles and advising graduate students, until her death. She is best known for her papers “A Defense of Abortion” and “Killing, Letting Die, and the Trolley Problem.”
    • Remembrance of Judith Jarvis Thomson, MIT
  • Since Roe v. Wade was overturned, at least ten states have banned abortion with no exceptions for rape or incest. But in 1971 Judith Jarvis Thomson presented a plausible argument that:
    • Abortion in the case of rape is morally justified, even if the fetus is a person
  • The argument is by analogy.

View Judith Jarvis Thomson’s Famous Violinist Argument

Derek Parfit’s Split Brain Thought Experiment

What are you?
You’d think the answer would be obvious — to you.

Two Theories of Persons

View Parfit’s Split Brain Thought Experiment

Brain in a Vat

View Brain-in-a-Vat Argument for Skepticism

Living Neurons Gradually Replaced with Synthetic Facsimiles
  • The human nervous system is a network of billions of neurons, each influencing the behavior of nearby neurons by transmitting molecules across synapses. When enough neurotransmitters are received at its input end, a neuron “fires” by sending a reversing voltage down its axon, releasing neurotransmitters at its output end. The neurotransmitters travel to nearby neurons, either contributing or inhibiting them from firing.
  • View Neural Determinism
  • Suppose scientists develop a synthetic neuron, functionally equivalent to a living neuron, whose ‘nucleus’ is a nanochip and whose ‘cell wall’ and other parts are made of silicon-based materials.
  • The synthetic neurons are used, successfully, to replace damaged parts of people’s brains.
  • Suppose all of person’s living neurons are gradually replaced by synthetic neurons, leaving them with a completely synthetic brain.
  • Is the person conscious like you and me and everyone else with a normal living brain? Or is the “person” no more conscious than a supercomputer or a sophisticated robot? Has he become what philosophers call a philosophical zombie?
John Rawls’ Original Position
  • John Rawls from the Britannica
    • American political and ethical philosopher, best known for his defense of egalitarian liberalism in his major work, A Theory of Justice (1971). He is widely considered the most important political philosopher of the 20th century.
  • Suppose you belong to a group responsible for determining the basic principles of government. So that the selection of the principles won’t be influenced by self-interest, imagine no one in the group knows anything about him or herself: gender, race, religion, age, intelligence, ethnicity, physical appearance, genetic makeup, natural abilities and disabilities, health, social or economic class, wealth, income, talents, etc. Behind this veil of ignorance, what basic principles of government would rational people acting in their own interest agree on?
  • Rawls argues people would agree on the following principles:
    • Each person has an equal right to the most extensive basic liberty compatible with a similar liberty for others.
    • Social and economic inequalities are arranged so that they are both
      • to the greatest benefit of the least advantaged
        • this is the Difference Principle
      • attached to offices and positions open to all under conditions of fair equality of opportunity.
  • Rationale for the Difference Principle:
    • Since a person’s natural talents and the socioeconomic circumstances in which he is born and raised are not his doing and beyond his control, “those who have been favored by nature, whoever they are, may gain from their good fortune only on terms that improve the situation of those who have lost out.” (John Rawls, A Theory of Justice, Page 101)
  • Britannica Political Philosophy
    • Why suppose with Rawls that justice requires an approximately egalitarian redistribution of social and economic goods? After all, a person who prospers in a market economy might plausibly say, “I earned my wealth. Therefore, I am entitled to keep it.” But how one fares in a market economy depends on luck as well as effort. There is the luck of being in the right place at the right time and of benefiting from unpredictable shifts in supply and demand, but there is also the luck of being born with greater or lesser intelligence and other desirable traits, along with the luck of growing up in a nurturing environment. No one can take credit for this kind of luck, but it decisively influences how one fares in the many competitions by which social and economic goods are distributed. Indeed, sheer brute luck is so thoroughly intermixed with the contributions one makes to one’s own success (or failure) that it is ultimately impossible to distinguish what people are responsible for from what they are not. Given this fact, Rawls urges, the only plausible justification of inequality is that it serves to render everyone better off, especially those who have the least.