Dualism and Physicalism

Philosophy of Mind: Dualism vs. Physicalism

The Fundamental Question

  • What are you, fundamentally? What would a magical photograph reveal about your true nature?

Two Competing Theories

1. Dualism (Substance Dualism)
  • Core Idea: You are a soul residing within a body.
  • The soul is your consciousness, the thinking part of you.
  • You (the soul) are fundamentally distinct from your body.
  • The soul can, in principle, exist without the body (e.g., afterlife).
  • Historical Context: Defended by René Descartes and many others; implicit in various religions.
2. Physicalism
  • Core Idea: You are entirely physical; there is no soul.
  • Everything about you can be explained through science and physics.
  • You are your body or your brain.
  • Consciousness and mental states are reducible to brain states.
  • You cannot exist without your body, as you are your body.
  • Contemporary View: Supported by the majority of contemporary neuroscientists.

Descartes' Argument for Dualism: Leibniz's Law

Premise 1: Leibniz's Law (Indiscernibility of Identicals)
  • If xx and yy do not share all the same properties, then xx is not identical to yy.
  • Example: Taylor Swift and Katy Perry
    • Taylor Swift was born in 1989.
    • Katy Perry was born in 1984.
    • Therefore, Taylor Swift is not Katy Perry.
Premise 2: Mental States vs. Brain States
  • Consider the mental state of hunger.
  • Question: Is hunger triangular or circular?
  • Answer: The question is meaningless; hunger does not have a shape.
  • Mental states, in general, do not have shapes.
  • However, the brain does have a shape (a mushy, football-like shape).
Conclusion
  • Mental states (like hunger) are not identical to brain states because they have different properties (shape).
  • This contradicts physicalism, which asserts that everything about you is physical.
Significance
  • This argument suggests that mental states are non-physical.

Divisibility Argument

Premise 1: Leibniz's Law
Premise 2: Divisibility of Brain vs. Mental States
  • The brain can be physically divided (though it would be fatal).
  • Mental states (like hunger) cannot be physically divided.
  • It makes no sense to