Section 1.3 The Laboratory of the Mind

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Section 1.3The Laboratory of the Mind

• Thought Experiments

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Philosophical Theories andThought Experiments

• Philosophical theories explain how its possible
  (or why its impossible) for a concept to apply
  by identifying the conditions for applying it.
• Thought experiments test such theories by
  determining whether the conditions identified are
  necessary or sufficient.

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Thought Probe Platonic Humans

• Plato once claimed that human beings are
  featherless bipeds (creatures that walk on two
  legs).
• Can you conceive of a featherless biped that is
  not a human being or a human being that is not a
  featherless biped?

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Aristotles Human Being

• According to Aristotle, human beings are
  rational animals.
• To test this theory, we must derive a test
  implication. We need determine whether all and
  only human beings are rational animals.
• Thought experiment Can you think of any human
  beings that are not rational animals or vice
  versa?

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Aristotles Human Being (revised)

• Test implication Infants are rational animals.
  If all and only human beings are rational
  animals, then infants are rational animals,
  because infants are human beings.
• Counterexample Human infants are human beings,
  but they are not rational.
• Revised theory All human beings are animals that
  have the capacity to be rational.
• Thought experiment Can you conceive of a human
  being that does not have the capacity to be
  rational or of a non-human animal that has the
  capacity to be rational?

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Aristotles Human Being (revised)

• Our argument against Aristotle goes like this
• (1) If human beings are rational animals, then
  human infants must be rational animals. (2) But
  human infants arent rational animals. (3)
  Therefore its not necessarily true that human
  beings are rational animals.
• The form of this argument is denying the
  consequent.

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Case Study Explaining How Moral Abortions Are
Possible

• Murder is the unjust killing of a person.
• So to determine whether abortion is murder, we
  have to determine whether a fetus is a person.

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Persons

• Persons are beings with full moral rights,
  including the right to life.
• What makes something a person? Why do normal
  adult humans have full moral rights but not cows,
  pigs, and chickens?

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Thought Experiment Warrens Moral Space Traveler

• Imagine a space traveler who lands on an
  unknown planet and encounters a race of beings
  utterly unlike he has ever seen or heard of. If
  he wants to be sure of behaving morally toward
  these beings, he has to somehow decide whether
  they are people, and hence have full moral
  rights. What should he look for?

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Warrens Criteria for Personhood

• Consciousness
• Reasoning (the developed capacity to solve new
  problems)
• Self-motivated activity
• The capacity to communicate messages of an
  indefinite variety of types
• Self-consciousness

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Thought ProbeThe Terri Schiavo Case

• According to Locke and Warren, a person is
  conscious, self-aware, and capable of reasoning,
  communicating, and engaging in self-motivated
  activity.
• If Terri Schiavo was in a persistent vegetative
  state, and if people in PVS have permanently lost
  the ability to think, was Terri Schiavo still a
  person?
• If Terri Schiavo was not a person, was removing
  the feeding tube an act of murder?

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How are thought experiments possible?

• We may have a concept and not be able to state
  the criteria for applying it.
• Philosophical inquiry tries to make explicit
  whats implicit in our understanding of a
  concept.
• Thought experiments test theories about the
  conditions under which concepts apply.

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Criticizing Thought Experiments

• The value of any experiment is determined by the
  amount of control with which it is executed.
• If an imaginary situation is not described in
  sufficient detail, the results of the experiment
  may be questionable.
• The best way to show that an experiment is
  unreliable is to conduct a better one.

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Conceivability and Possibility

• The best evidence that a situation is possible is
  that its conceivable.
• But from the fact that something seems
  conceivable, it doesnt follow that it is
  conceivable.
• Time travel seems conceivable but isnt because
  it leads to a contradiction.

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Scientific Thought Experiments

• Any theory that implies a contradiction cannot be
  true.
• Scientists use thought experiments to test for
  contradictions.

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Thought Experiment Aristotles Theory of Motion

• Aristotle thought that a heavier object would
  fall faster than a lighter one.
• Imagine that a heavy cannonball is attached to a
  light musket ball by means of a rope. Now imagine
  that both this combined system and an ordinary
  cannonball are dropped from a height at the same
  time. What will happen?

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Thought Experiment Tooleys Cat

• Suppose a cat was accidentally given an injection
  that would cause its brain to develop into one
  with the same capabilities as ours.
• Would it be wrong to kill the cat before the
  brain was fully developed?

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Thought Experiment Thomsons Diseased Musician

• Suppose that a musician with a fatal kidney
  ailment had his bloodstream attached to yours
  because you are the only person with the right
  blood type.
• If you allow him to stay plugged in for nine
  months, he will lead a normal life.
• Are you morally obligated to stay plugged in?