Introduction: The World of Physicalism
Welcome to one of the most exciting parts of the Metaphysics of Mind! So far, you might have looked at Dualism—the idea that the mind and body are two separate things. Physicalism takes a totally different approach. Physicalists argue that there is no "ghost in the machine." Instead, everything about the human mind can be explained by physical stuff.
Don't worry if this seems a bit strange at first. We are going to break down the three main physicalist theories step-by-step. By the end of these notes, you’ll see how philosophers try to prove that your thoughts, feelings, and "self" are just part of the physical world.
1. What is Physicalism?
At its heart, Physicalism is the view that everything is physical. This includes objects (like your phone), events (like a football match), and even your mind. Philosophers use a special word called supervenience to explain this.
Supervenience: One set of facts (the mind) "supervenes" on another (the brain) if you cannot have a change in the mind without a change in the brain.
Analogy: Think of a digital photo on a screen. The "image" (the mind) supervenes on the "pixels" (the physical). You can't change the image without changing the pixels. If the pixels are exactly the same, the image must be exactly the same!
Quick Review: Physicalism = The mind is physical. No "soul" or "non-physical" mind exists independently of the body.
2. Philosophical Behaviourism
Behaviourists argue that when we talk about "mental states" (like being happy or in pain), we aren't talking about some private thing happening inside your head. We are actually talking about outward behaviour.
'Hard' Behaviourism (Carl Hempel)
Hempel argued that all talk about the mind can be reduced to talk about physics. He believed that a statement like "Paul is in pain" means the same thing as "Paul is crying, his blood pressure has risen, and he is rubbing his leg." There is no "pain" over and above these physical movements.
'Soft' Behaviourism (Gilbert Ryle)
Ryle thought Hempel was a bit too strict. He argued that mental states are actually dispositions. A disposition is how something is likely to behave in certain circumstances.
Analogy: Think of a glass vase. We say it is "brittle." This doesn't mean it is breaking right now; it means that if you dropped it, it would break. Ryle says "being in pain" is like being brittle. It means you are disposed to wince or cry out if someone touches you.
Issues with Behaviourism
1. Multiple Realisability: People react to the same mental state in different ways. If I’m angry, I might shout. If you’re angry, you might get very quiet. If "anger" is just behaviour, how can two different behaviours be the same mental state?
2. Circularity: To explain one mental state, you often have to mention another. To explain my "thirst" (behaviour: drinking water), you have to mention my "belief" that the water isn't poisonous. But a "belief" is a mental state too! You end up going in circles.
3. The "Super-Spartans" (Hilary Putnam): Imagine a race of "Super-Spartans" who feel intense pain but have trained themselves never to show it. No wincing, no crying. Behaviourism would say they aren't in pain because they have no "pain behaviour." But we know they are in pain! This suggests the mental state is different from the behaviour.
Key Takeaway: Behaviourism claims the mind is just what we do (behaviour) or what we are likely to do (dispositions).
3. Mind-Brain Type Identity Theory
This theory is much more direct. It claims that mental states are brain states. They are the exact same thing.
Ontological Reduction: This means that while the words "pain" and "C-fibres firing" mean different things, they refer to the same thing in the real world.
Analogy: In the past, people talked about "The Morning Star" and "The Evening Star." Later, scientists discovered they are both actually the planet Venus. They are "identical." Identity theory says "Pain" and "C-fibres firing" are just like that.
Issues with Identity Theory
Multiple Realisability of Mental States: This is the biggest problem for Identity Theory. If "Pain" is identical to "Human C-fibres firing," then an octopus or an alien without C-fibres could never feel pain. However, it seems very likely that other creatures can feel pain even if their brains are wired differently than ours!
Quick Review: Identity Theory = Pain IS a specific physical process in the brain.
Memory Aid: "Identity" means they are identical—like Clark Kent and Superman.
4. Eliminative Materialism
This is the most "extreme" physicalist view, defended by Paul and Patricia Churchland. They argue that our common-sense way of talking about the mind (using words like "belief," "desire," or "hope") is actually a mistaken theory called Folk Psychology.
The Core Idea: Science will eventually prove that "beliefs" and "desires" don't actually exist at all. We should stop using these words and instead use neuroscience to explain ourselves.
Analogy: In the Middle Ages, people explained diseases using "bad air" or "witches." Once we discovered germs and viruses, we eliminated the talk of witches because they didn't exist. The Churchlands say "beliefs" are just like "witches"—a bad explanation that science will replace.
Issues with Eliminative Materialism
1. It is self-refuting: To argue for Eliminative Materialism, the Churchlands must believe it is true. But their theory says "beliefs" don't exist! If they have no beliefs, how can they have a theory?
2. Folk Psychology has good predictive power: Common-sense psychology actually works quite well. If I know you "desire" cake and "believe" there is cake in the fridge, I can predict you will walk to the fridge. Why throw away a theory that works?
3. Certainty of mental states: Descartes argued that the one thing we can be absolutely sure of is our own mind. Eliminative Materialism asks us to give up the thing we are most certain of!
Key Takeaway: Eliminative Materialism says our common-sense ideas about the mind are false and will be replaced by brain science.
Summary Table: Which is Which?
Behaviourism: Mind = What we do.
Identity Theory: Mind = What the brain is.
Eliminative Materialism: Mind = A failed theory we should get rid of.
Common Mistake to Avoid:
Don't confuse Identity Theory with Behaviourism. Identity Theory looks inside at the brain cells. Behaviourism looks outside at how the person is acting. If you talk about "neurons firing," you are talking about Identity Theory!
Don't worry if this feels like a lot to take in! Philosophy is about questioning things we take for granted. Just remember: Physicalists are all trying to explain the mind using the same rules we use for the rest of the physical universe.