The 'hard problem' of consciousness

The 'hard problem' of consciousness

The hard problem of consciousness: Can science explain what its like to have experiences? Two views on yourself From the outside: a human body A physical object with spatial properties & physical structure. A complex biological organism whose behavior is controlled by a nervous system & brain. A system evolved from single-celled organisms, through a process of natural selection. Its behaviour is fully explained by physical mechanisms: brain activity is just electro-chemical interactions among cells

From the inside: a unified center of consciousness a mind Capable of knowing about its environment via sensations. Capable of having emotions, goals, beliefs. Capable of reasoning: thoughts and feelings interact in intelligent ways to produce new thoughts. Capable of acting: mental states cause cause bodily behavior. How are these two perspectives related? Physicalism vs Dualism Physicalism: everything that exists is fully determined by micro-physical properties. Dualism: there are two fundamentally different kinds of thing in the world mental & physical and neither fully

determines the other. The all-powerful creator test: if you put all the worlds physical properties in place, have you thereby created every property that actually exists? Chemical properties? Geological properties? Biological properties? Psychological properties? A hard case

Qualia = the what its like aspect of experience = subjective, qualitative, phenomenal properties: the hurtfulness of pains the itchiness of itches the pangs of jealousy the queasiness of nausea the look of red What are qualia like?

If you have to ask, you aint never going to know! (Louis Armstrong) Qualia = how your experiences seem to you from the inside. So you have direct knowledge of your own qualia, just by being in a perceptual state. What about others qualia...? Nagel on being a bat Most bats use sonar to locate things in space: They emit high-pitched shrieks Their brains correlate these outputs with resulting echoes to allow them to discriminate objects in their environment. Echolocation detects spatial properties: distance, location, trajectory, size, texture, etc.

What is it like to be a bat? Qualia: It seems impossible to imagine the intrinsic feelings of sonar. Subjective perspective: Whats the bats own subjective perspective on their sonar experiences? An explanatory gap in science? 1. There is something its like to be a bat. 2. But we cant imagine what its like: What the experience of sonar is like. What its like from the bats own perspective. (Nagel, 220-1)

3. No amount of scientific facts about bats brains & cognitive structure will ever allow us to understand these what its like facts. (Nagel, 222-3) 4. So theres an explanatory gap: the physical sciences can never fully explain the facts about the subjective aspects of experience. (Nagel, 223) 5. So the physical sciences are not a complete account of every aspect of the world. Nagel on physicalism 1. If the physical sciences cant explain the subjective what its like facts, there is a gap in our understanding of the world. 2. But does it follow that physicalism is false?

The world contains extra non-physical properties over & above the totality of physical properties? 3. Nagel: No, not necessarily: Physicalism could still be true even if we cant understand why its true. It may be a brute inexplicable fact that this subjective feeling = audio cortex state AC34. Australian Materialists Ullin Place Jack Smart David Lewis

David Armstrong 8 The argument from parsimony 1. Mental states play important causal roles: Your yellow sensation = the state thats: Typically caused by: bananas, wattle, lemons Can causally interact with other mental states: beliefs about what youre seeing, home decorating decisions, reports of your sensations... Can causally affect behavior: which banana to eat, which paint to choose for your bedroom, 2. Science: what plays these causal roles = brain states. 3. Occams razor: Dont posit more entities than are strictly needed to explain the observed effects.

Dualist qualia arent needed to explain bodily behaviour! 4. So: mental states = brain states: yellow sensation = a specific state of visual cortex An objection Brain states explain the entire physical causal process from sensory stimulation to behavioural outputs. Occams razor: we dont need to posit any dualist qualia to explain any observed physical states. But: can physical states really explain everything? Occams razor doesnt tell you to ignore facts that you directly observe!

But we directly observe our own qualia. Explanatory gap: these cant be explained by science. So the physicalist argument from parsimony seems inconclusive: If we want to explain qualia, purely physical facts will not suffice. Arguments for qualia dualism Ren Descartes David Chalmers Conceivable disembodiment

Conceivable Zombies Descartes: disembodied minds! Can you coherently imagine being a pure center of conscious awareness without having a body? Is there any contradiction in the very idea of a disembodied center of consciousness? Skeptical scenario: an all-powerful malicious demon could in principle deceive me into thinking I had a body and a brain when I didnt Disembodied conceivability 1. My mind =df a thinking thing: a center of consciousness with beliefs, emotions, qualia, etc. 2. My body =df an extended physical thing: an object with shape,

location, mass, etc. 3. Theres no contradiction in the idea of my mind existing without my body. 4. If theres no contradiction in conceiving one thing existing without another, then its really possible for them to exist separately. 5. So: its really possible for minds to exist without bodies. 6. So: minds bodies. So physicalism is false: if an all-powerful god recreated all the physical objects of our world, shed have to add all the minds on top. Chalmers: Zombies! Philosophical zombies = perfect physical & functional duplicates of human beings, with no qualia. Daves zombie twin: 1. Physical brain activity is exactly like Daves.

2. Functional organisation exactly like Daves brain. 3. Acts, reacts, reasons, & talks exactly like Dave: Tries skateboarding: acts exactly as you would. Falls: ow!, that hurts!!, Im in pain!!!, help me!!!! 4. But Daves zombie twin has no conscious experiences: theres nothing its like to be your zombie twin No pains no visual, tactile, auditory, emotional qualia the lights are out! Chalmers: Zombies! Philosophical zombies = perfect physical and functional duplicates of human beings, with no qualia.

Daves zombie twin: 1. Physical brain activity is exactly like Dave. 2. Functional organisation exactly like Daves. 3. Acts, reacts, reasons, & talks exactly like Dave: Tries skateboarding: acts exactly as you would. Falls: ow!, that hurts!!, Im in pain!!!, help me!!!! 4. But Daves zombie twin has no conscious experiences: theres nothing its like to be your zombie twin No pains no visual, tactile, auditory, emotional qualia the lights are out! Dave

Zombie Dave Are zombies really possible? 1. Is there any contradiction in the idea of a perfect physical duplicate of you without any sensory qualia? 2. Could an all-powerful creator create a physical duplicate of you without any what its like properties? 3. If so, then qualia are extra properties over & above all the physical properties so dualism is true! Zombie conceivability Zombies = perfect physical duplicates of us, with no qualia.

1. 2. 3. 4. 5. 6. Zombies are conceivable: theres no hidden logical contradiction in the idea of zombies. So zombies are really possible: an all-powerful god could have created zombies. So qualia are extra, non-physical properties: they are independent of physical & functional properties. Were not zombies: we have qualia. So we have non-physical mental properties (qualia).

So physicalism is false about us! The keys to dualist arguments We know we have qualia. We cant explain why qualia & brain states are correlated. Its coherent to imagine the possibility of the two properties coming apart. If qualia & brain states can come apart, then they must be independent properties. Hard problems of consciousness Assume: Science has identified the neural correlates of sensory experiences in humans & other animals: e.g. A bats echolocating prey = audio cortex state AC34

1. What is it like to be in AC34? 2. Why does being in AC34 feel like that? 3. Is there a non-physical what its like property over & above AC34? Scientific inquiry cant answer these hard questions! 1. A question about subjective imagination/experiences. 2. A question connecting objective to subjective experience. 3. A metaphysical question. Can we answer these questions through philosophy?

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