– Contemporary philosophical defenders of dualism have rather different views from those Descartes had.
• They are more interested in consciousness.
• Even if Physicalism can explain a lot of things, it can’t explain conscious experience.

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Conscious Experience:
– When philosophers talk about consciousness, we have a very precise type of issue in mind.
– By Conscious experience, philosophers mean issues about what it’s like to have certain experiences:
• What it’s like to see red.
• …
– These mental states are called qualia .
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Also called raw feels or sense data.

– The easiest way to get the idea of qualia is to think about people who are experiencing the same things you are, but have different qualia.
• The colorblind person…
• The Qualia of Driving:
– Have you ever had the experience of a long drive?
• Zoning out and the missing Qualia…

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Inverted Qualia:
– Suppose that there’s someone who, from birth, when they see red, has just the experience you have when you see blue and vice versa.
– Their red and blue qualia are reversed, or inverted.
– They call the color of a ripe tomato ‘red’ even though their qualia is like your blue qualia…
– Can you tell from someone’s behavior that they’re suffering from inverted qualia ?

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Qualia: trouble for Physicalism:
– What we’ve said about qualia so far is already trouble for some kinds of physicalism.
– The Behaviorist can’t allow for the possibility of inverted qualia, since people with inverted qualia would behave just like the rest of us.
– What about the identity theorist?

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Frank Jackson (1943-present)
• An Australian philosopher.
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Most famous for his knowledge argument for dualism.
• He has actually given up dualism now, but he still thinks the argument is valid.
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He is known for giving very convincing, commonsensical arguments

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The Mary Thought Experiment:
– Imagine a woman Mary
– Mary is a brilliant scientist who’s been imprisoned for life in a room painted entirely black and white.
– Even Mary herself is painted.
– She conducts experiments (viewing the results through black and white TV) and learns every physical fact about the mind.
• The physical properties of color and the eye’s response to light…
• What Mary doesn’t know:
– Even after Mary has learned every physical fact, she still doesn’t know what it’s like to see the color red.
– Imagine what happens when she steps outside of the room for the first time and sees a ripe tomato.

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Thought experiments:
– Jackson’s example of Mary is a thought experiment.
– A thought experiment is a constructed case which is used to test our intuitions about some philosophical puzzle...
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So Jackson constructs the Mary thought experiment to test our intuitions about Dualism.
– In particular, the Mary experiment is supposed to lead us to the intuition that Mary learns a nonphysical fact…

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The Knowledge argument:
– Jackson takes the Mary thought experiment as evidence against
Physicalism
– His argument is known as the Knowledge argument:
• 1. Mary knows every fact about the physical world.
• 2. Mary learns a fact about qualia, which she didn’t previously know, when she steps out of the black and white room.
• 3. Thus, facts about qualia are facts about the nonphysical.
• 4. Thus, Physicalism is false.
• 5. Thus, Dualism is true.

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Epiphenomenalism:
– A thing is epiphenomenal if and only if it can be caused by other things, but never causes anything itself.
– According to Jackson, Qualia are epiphenomenal.
• Qualia are caused by physical states, such as brain states, but they do not have any physical effects.
• So there are two types of Dualists:
– Interactionists like Descartes: the non-physical aspects of the mind have physical causes and physical effects.
– Epiphenomenalists like Jackson: the non-physical aspects of the mind have physical causes but no physical effects.

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Although the Epiphenomalist thinks Qualia are non-physical states, he does allow that some mental states are physical states .
– Belief states and desire states are physical states:
• According to the Epiphenomenalist, only physical states can cause other physical states.
• And Belief states and Desire states are physical states because they cause actions.
• Beer in the fridge example…

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The Problem of other minds:
– Epiphenomenalism suffers from the problem of other minds…
– Someone who lacks all Qualia is called a zombie.
– According to epiphenomenalism, zombies would be physically just like us…
– So how could I tell that you’re not a zombie?

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Could we even know Epiphenomenalism was true:
– Suppose epiphenomenalism was true.
– Suppose I’ve convinced you all with Jackson’s argument.
– At no point did qualia play any causal role in the argument that convinced you.
• How then can the Knowledge argument be a good reason to believe its conclusion?

– How should the Physicalist think about qualia?
– What should the Physicalist say about inverted qualia?
– How should the Physicalist reply to the knowledge argument? Two options:
• Mary wouldn’t learn anything new when she leaves the black and white room.
• Mary would learn something, but not a new fact.

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The first Physicalist response is to Deny the intuition:
– Some physicalists deny that Mary would learn anything new when she leaves the black and white room.
– The point of the description of the case, the black and white room, etc., was to get us to have the intuition that she would say ‘Ah, ha!…’.
– But we can only have the intuition if we are genuinely able to imagine the case as described.
• Maybe we can’t imagine Jackson’s Mary experiment:
– …because we can’t imagine what someone would do who knew every physical fact.
• Jackson’s reply:
– but you only have to imagine Mary knows every relevant fact.

• The Second Physicalist response: Mary doesn’t learn a new fact:
– Mary doesn’t learn a new fact, she acquires the ability to distinguish red things from dark grey things…
– Riding a bike:
• Learning to see red is like learning to ride a bike: they can’t be learned in a book…
• So Knowing how to do something is not the same as knowing that something is true.
• Jackson’s reply:
– But Mary always had the ability to distinguish red things from dark grey things.
– Is this response adequate?