1. The ‘hard problem’ of consciousness:
Can science explain
‘what it’s like’ to have experiences?

2. Two views on yourself  How are these two perspectives related?
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?
– it’s ultimately powered by electrical chemical reactions within and between cells

3. 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 world’s physical properties in place, have you thereby created every property that actually exists?
Chemical properties?
Geological properties?
Biological properties?
Psychological properties?

4. A hard case
Qualia = the ‘what it’s 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 ain’t 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...?
Substance monism: all objects are physical
Property dualism: physical objects can have non-physical mental properties.

5. 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: What’s the bat’s own subjective perspective on their sonar experiences?
What it’s like to be myopic and boring – Kathleen Akins

6. An explanatory gap in science?
There is something it’s like to be a bat.
But we can’t imagine what it’s like:
What the experience of sonar is like.
What it’s like from the bat’s own perspective. (Nagel, 220-1)
No amount of scientific facts about bats’ brains & cognitive structure will ever allow us to understand these what it’s like facts. (Nagel, 222-3)
So there’s an explanatory gap: the physical sciences can never fully explain the facts about the subjective aspects of experience. (Nagel, 223)
So the physical sciences are not a complete account of every aspect of the world.

7. Nagel on physicalism
If the physical sciences can’t explain the subjective ‘what it’s like’ facts, there is a gap in our understanding of the world.
But does it follow that physicalism is false?
The world contains extra non-physical properties over & above the totality of physical properties?
Nagel: No, not necessarily: Physicalism could still be true – even if we can’t understand why it’s true.
It may be a brute inexplicable fact that
this subjective feeling = audio cortex state AC34.

8. “Australian Materialists”
Ullin Place
Jack Smart
David Armstrong
Both Place & Smart at Adelaide, students of Ryle
David Lewis

9. The argument from parsimony
Mental states play important causal roles:
Your yellow sensation = the state that’s:
Typically caused by: bananas, wattle, lemons…
Can causally interact with other mental states: beliefs about what you’re seeing, home decorating decisions, reports of your sensations...
Can causally affect behavior: which banana to eat, which paint to choose for your bedroom, …
Science: what plays these causal roles = brain states.
Occam’s razor: Don’t posit more entities than are strictly needed to explain the observed effects.
 Dualist qualia aren’t needed to explain bodily behaviour!
––––
So: mental states = brain states:
yellow sensation = a specific state of visual cortex

10. An objection
Brain states explain the entire physical causal process from sensory stimulation to behavioural outputs.
Occam’s razor: we don’t need to posit any dualist qualia to explain any observed physical states.
But: can physical states really explain everything?
Occam’s razor doesn’t tell you to ignore facts that you directly observe!
But we directly observe our own qualia.
Explanatory gap: these can’t be explained by science.
So the physicalist argument from parsimony seems inconclusive:
If we want to explain qualia, purely physical facts will not suffice.

11. Arguments for qualia dualism
René Descartes David Chalmers
Conceivable disembodiment Conceivable Zombies

12. 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 didn’t…

13. Disembodied conceivability
My mind =df a thinking thing: a center of consciousness with beliefs, emotions, qualia, etc.
My body =df an extended physical thing: an object with shape, location, mass, etc.
There’s no contradiction in the idea of my mind existing without my body.
If there’s no contradiction in conceiving one thing existing without another, then it’s really possible for them to exist separately.
So: it’s really possible for minds to exist without bodies.
So: minds ≠ bodies.
 So physicalism is false: if an all-powerful god recreated all the physical objects of our world, she’d have to add all the minds on top.

14. Chalmers: Zombies!
Philosophical zombies = perfect physical & functional duplicates of human beings, with no qualia.
 Dave’s zombie twin:
Physical brain activity is exactly like Dave’s.
Functional organisation exactly like Dave’s brain.
Acts, reacts, reasons, & talks exactly like Dave:
Tries skateboarding: acts exactly as you would.
Falls: ‘ow!’, ‘that hurts!!’, ‘I’m in pain!!!’, ‘help me!!!!’
But Dave’s zombie twin has no conscious experiences: there’s nothing it’s like to be your zombie twin
No pains
no visual, tactile, auditory, emotional qualia
‘the lights are out!’

15. Chalmers: Zombies!
Philosophical zombies = perfect physical and functional duplicates of human beings, with no qualia.
 Dave’s zombie twin:
Physical brain activity is exactly like Dave.
Functional organisation exactly like Dave’s.
Acts, reacts, reasons, & talks exactly like Dave:
Tries skateboarding: acts exactly as you would.
Falls: ‘ow!’, ‘that hurts!!’, ‘I’m in pain!!!’, ‘help me!!!!’
But Dave’s zombie twin has no conscious experiences: there’s nothing it’s like to be your zombie twin
No pains
no visual, tactile, auditory, emotional qualia
‘the lights are out!’
Dave
Zombie Dave

16. Are zombies really possible?
Is there any contradiction in the idea of a perfect physical duplicate of you without any sensory qualia?
Could an all-powerful creator create a physical duplicate of you without any ‘what it’s like’ properties?
If so, then qualia are extra properties over & above all the physical properties – so dualism is true!

17. Zombie conceivability
Zombies = perfect physical duplicates of us, with no qualia.
Zombies are conceivable: there’s 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.
We’re not zombies: we have qualia.
So we have non-physical mental properties (qualia).
So physicalism is false about us!
Assumes: we have clear & distinct idea of qualia & of physical/functional properties

18. The keys to dualist arguments
We know we have qualia.
We can’t explain why qualia & brain states are correlated.
It’s coherent to imagine the possibility of the two properties coming apart.
If qualia & brain states can come apart, then they must be independent properties.

19. Hard problems of consciousness
Assume: Science has identified the neural correlates of sensory experiences in humans & other animals:
e.g. A bat’s echolocating prey = audio cortex state AC34
What is it like to be in AC34?
Why does being in AC34 feel like that?
Is there a non-physical ‘what it’s like’ property over & above AC34?
Scientific inquiry can’t answer these hard questions!
A question about subjective imagination/experiences.
A question connecting objective to subjective experience.
A metaphysical question.
Can we answer these questions through philosophy?
Activation of auditory cortex area 34.
A subjective experiential/imaginistic question.
Two explanatory questions
A metaphysical question.