Materialism

Psy391D - Class 3

(This page last updated 16 September, 2004.)

Supplemental Reading In his book Consciousness Explained, Daniel Dennett outlines his goals for an explanation of consciousness and explains why he finds dualism unacceptable (pp. 21-42). Pages 23-49 from Churchland's book Matter and Consciousness cover Philosophical Behaviorism, Identity Theory, Functionalism and Eliminative Materialism.

At this point we have finished covering the different types of dualism. Now we consider materialism, the belief that nothing exists beyond the material world, and that we can study it all with physical science (physics, chemistry, etc.). As you will see, there is even more variety in types of materialism than there was in types of dualism.

• Philosophical Behaviorism
  • Redefines our talk about mental states.
  • Everything is described in terms of behaviors that can be objectively observed. (operational definitions)
    • "Joe is in pain."
      • He screams and yells.
      • He hops around on one foot.
      • He takes aspirin.
      • If you ask him if it hurts, he responds "Yes".
  • If Philosophical Behaviorism works, then mental states are less of a problem for science, because they can be reduced to observable bahaviors that can be studied scientifically.
  • problems
    • No explanation for the inner aspect of our mental states.
    • Definitions required for mental states just too complex.
• Identity Theory (Reductive Materialism)
  • Each mental state corresponds to a specific physical (brain) state
    1. sound = compression waves in air
    2. color = reflectance properties
    3. heat = average molecular kinetic energy
    4. mental state = brain state
  • 1-3 above are all examples of successful intertheoretic reduction.
  • Must be a one-to-one correspondence between mental states and physical states.
  • Arguments for Identity Theory
    • Each individual seems to originate from purely physical things.
    • Evolution seems to explain how our species (and others) came to be.
    • Every aspect of our mental life seems to rely on neural activity.
    • Neuroscience is making progress in explaining more and more of the mind.
  • Arguments against Identity Theory
    • introspection
    • category errors
      • Brain processes have specific locations, but mental processes do not.
      • Mental states have meaning, but brain states do not.
    • special nature of experience
      • The only way to know what it is like to have a particular sensation is to experience that sensation.

Types and Tokens

In this context, a token is a specific thing, while a type is a category made up of many tokens that share certain relevant properties. For instance, think of all the parrots in the world. Each one is a separate thing, and thus a separate token, but they are all of the same type, "parrot."

Identity theory holds that each type of mental state (for instance, believing that it is raining) will always correspond to the same type of physical state in the brain.On the other hand, Functionalism holds that each token of a mental state will correspond to some token physical state, but that all the mental states of one type will not necessarily all correspond to physical states of the same type. For instance, the events that occur in my brain when I believe it is raining may be very different from the events occurring in your brain when you believe it is raining. According to Functionalism, both of our beliefs correspond to specific brain states, but your brain state and my brain state can be very different.

Folk Psychology refers to the theories we all use to predict each other's behavior. We all assume that other people have certain beliefs, desires, etc., and we use these assumptions to predict their behavior. For instance, you might theorize that I believe that our class meets in room 3051, and from that you can predict that at class time I will walk to room 3051. Folk psychology is not a theory that was worked out explicitly by psychologists, but a set of ideas we all use in everyday life.

• Functionalism
  • Mental state defined by causal relations.
    • to stimuli
    • to behaviors
    • to other mental states
      • This is the part that makes it unlike Behaviorism. In Behaviorism, each mental state had to be defined in terms of observables such as stimuli and behaviors. One mental state could not be defined in terms of another mental state.
  • Under Identity Theory, only those who have the same brain states that we have can have the same mental states. Under Functionalism, Martians with brains made out of green cheese can still have the same mental states that we do, as long as they have the same functional states that we have.
  • Implies that the mind can be studied without knowing about the brain.
  • arguments against functionalism
    • Can't explain qualitative nature of mental states.
      • inverted spectrum
      • absent qualia
        • everyone in China simulating a brain
• Eliminative Materialism
  • Rejection of our common sense psychology.
    • Our current ideas about mental states (beliefs, desires, etc.) are wrong.
  • Some day we will arrive at a better way of explaining the brain.
  • Examples of other scientific concepts that have been replaced by different ones.
    • caloric replaced with kinetic theory of heat
    • phlogiston replaced by oxidation
    • "starry sphere of the heavens" replaced by rotating earth
    • demon possession replaced by psychosis
  • So many folk theories have been wrong, it would be amazing is folk psychology were correct.
  • arguments against eliminative materialism
    • We are aware of our own beliefs and desires, so they must exist.
      • Maybe our introspections are shaped by our own folk theories.
    • In order to believe eliminative materialism, you must first believe that beliefs exist.
      • The same thinking argues we should still believe in vital spirit.

next class: Qualia

Psych 391D: Consciousness Kyle Cave Psychology Dept. U. Mass.