PHIL25501 Exam 1

Purdue Fall 2026, Prof. Sarah Robins

David Chalmers

The Hard Problem

Neuroscience explains physical processing, but doesn’t explain experience. Explaining experience is the “hard problem.”

• “easy problems” = attention, awake vs asleep, discrimination of stimuli

  • Not literally easy to solve, but solvable with science

• Even if all behavioral/cognitive functions explained, we still wouldn’t understand why it comes with subjective experience

Explanatory gap

Gap between physical explanation of what brain is doing and subjective experience of feeling.

• We have correlation between brain state X and conscious experience Y, but not causation X → Y

• Closely tied to Chalmer’s Hard Problem

Philosophical zombies

A hypothetical being that is physically and behaviorally identical to a human, but without any conscious experience.

• Still reacts and behaves like a human, but there is nothing it is like to be the zombie

• Chalmer’s thought experiment to explain the explanatory gap

• Shows that despite physically being identical, it doesn’t have subjective experience

Modal argument

Chalmer’s argument using philosophical zombies:

1. Zombies are conceivable

2. Conceivable = possible

3. Therefore zombies are possible

Types of “possible”:

• Physical possibility = consistent with laws of physics

• Metaphysical possibility = consistent with basic nature of reality

• Logical possibility = not contradictory

Chalmer’s claim is that if zombies are metaphysically possible, then consciousness is not purely determined by physical facts

Objection

Are zombies even conceivable? Does conceivability imply possibility? The argument is valid but is it sound?

Naturalistic Dualism

Chalmers’ view that consciousness is fundamental and irreducible feature of reality governed by connections between physical processes and conscious experience.

Principle of Structural Coherence

Although Chalmers’ considers consciousness and physical processing are distinct, he still believes they are structurally corresponded.

• Structure in awareness mirrors structure in experience

Principle of Organizational Invariance

Chalmers’ idea that if two things have the same abstract functional organization, they’ll both have same conscious experience.

Ex:) If we replace brain neurons with silicon chips while preserving same pattern of interactions, they should both have the same conscious experience.

Reductionism

Phenomena can be fully explained in terms of more basic things.

We will be able to fully explain the mind/consciousness once we can explain the more basic physical components.

• Chalmers disagrees, saying consciousness is irreducible so we won’t be able to explain it using more basic things

Physicalism

Everything that exists is fundamentally physical/material.

• Mind = body/brain

• Once all physical things are explained, mind should be fully explainable

Churchland’s Hornswoggle Problem

Churchland argues that Chalmers’ framing of the problem of consciousness as a uniquely difficult issue separate from other neuroscientific problem problems is misleading.

• Consciousness is difficult, but not distinctly so

• We shouldn’t say that consciousness can’t be explained by neuroscience yet

Left-Out Hypothesis

Churchland’s label for Chalmer’s claim that even after we solve all the “easy” problems (we can explain attention, memory, etc), consciousness wouldn’t be explainable (it’s left out)

Churchland’s criticism of Chalmers

Argument from ignorance = treating the current lack of knowledge as evidence that something can’t be explained.

• One of Churchland’s main criticisms of Chalmers

• Chalmers: neuroscience hasn’t been able to explain consciousness so far, therefore neuroscience can’t explain consciousness

• Churchland: just because we haven’t so far doesn’t mean it can’t be possible in future

Begging the question

• Using a premise that assumes the conclusion you’re trying to prove is already true

Conceivability vs possibility

• Just because you can conceive it doesn’t necessarily mean it’s possible

• Shouldn’t use epistemology to determine metaphysics

History of science

• Based on history, our intuitions on what is “easy”, “hard”, or explainable are not great

Jennan Ismael

• Ismael challenges the physicalist idea that pain = C-fibers firing

  • Whether you’re in pain or not is ultimately up to you, not whether C-fibers are firing or not

  • Knowing one doesn’t necessarily settle the other

• She believes consciousness is not special or unique (opposite of Chalmers)

“Here” Analogy

Thinker: Ismael

The analogy

• Compare “I am in pain” with “I am here”

• I can know “I am here” without knowing the precise coordinates

• “here” is not a separate mysterious location, it’s just an ordinary place relative to you viewed from your POV

• Same physical fact described with two different perspectives

• Epistemic difference doesn’t imply metaphysical difference

Science isn’t designed to be able to explain consciousness, and just because it can’t doesn’t mean consciousness is special

• Science shouldn’t be expected to explain what C-fibers firing feels like for me

• Hard problem is a pseudo-problem that we can ignore

Qualia

Thinker: Jackson

What an experience feels like

• Subjective phenomenal qualities of experience

• Ex:) taste of a lemon, painfulness of pain, what red looks like

Knowledge Argument

Thinker: Jackson

Thought experiment: Mary is goated scientist who knows all physical facts about color (light physics, biology of human eye, etc) but has always been trapped in a black and white room. When she goes outside, she will gain something new in seeing the color red for the first time despite knowing all the science behind it.

• Since she learned a new non-physical fact, this shows not all facts are physical, thus physicalism is false

• Arguing for a metaphysical difference, not just epistemic

Epiphenomenalism

Thinker: Jackson

• Qualia are caused by physical things, but themselves cause anything physical

• Instead of physical brain state → qualia → physical behavior, it’s qualia ← physical brain state → physical behavior

  • In other words, you didn’t flinch because you were in pain, you flinched and felt pain because of your physical brain state

• Doesn’t that make qualia useless?

  • Qualia could be a by-product of separate evolution

  • Ex:) Polar bear’s coat keeps it warm, but it’s also heavy. Heaviness isn’t an advantage, but comes with the coat anyways.

Property dualism

Thinker: Jackson

All things are physical things (only one type of substance), but these can possess both physical and mental properties

Ex:) Your brain has physical properties (i.e. neurons firing) and mental properties (i.e. qualia of seeing red)

Criticism of Jackson’s Knowledge Argument

Lewis - Mary gained a new ability, not new knowledge

• She gained abilities to identify red, imagine red, remember red

• Knowing-how is not the same as knowing-that

• Thus, knowledge argument doesn’t refute physicalism

• Ex:) You can know all there is about riding a bike, but still not know how to ride it

Levin - Mary gained knowledge of an old fact in a new way

• New way of representing an old fact, not an entirely new fact

• Ex:) You learn that person is my professor. Then you learn that person is Sarah. This doesn’t mean there are two people, just two ways of recognizing one

Cogito Argument

Thinker: Descartes

What can I know for certain?

• Senses can be deceiving

• I could be dreaming

• Reasoning could be manipulated by a deceiver

• Even if there is a deceiver, the fact that I is being deceived means I exist

• Cogito, ergo sum = “I think, therefore I am”

Even if everything else can be doubted, you cannot doubt your existence while thinking since doubting itself requires a thinker

The Wax Example

Thinker: Descartes

Wax has many physical properties, but they change once heated. How do you know it’s still wax?

• Not through sensation since the sensory properties are different

• Not through imagination since we cannot imagine every possible form wax can take

• We can through pure understanding/reason

• We know the essence of physical things through reason rather than the body, thus the mind is better known than the body

  • Better known = we know the existence/activity of the mind more than the body since senses can be misleading

Substance Dualism

Thinker: Descartes

Mind and body are two fundamentally different substances.

Mind

• A thinking thing

• Not spatial

• Indivisible

Body

• An extended thing

• Just matter that cannot think, understand, have ideas

• Can be divided and takes up space

Conceivability Argument

Thinker: Descartes

1. If I can vividly and clearly understand X as being F, then God can make X be F.

2. Therefore if I can vividly and clearly understand one thing as distinct from another, then it must be actually distinct since God can make it so

3. I can vividly and clearly imagine myself as a thinking, non-extended thing.

4. I can vividly and clearly imagine my body as a non-thinking, extended thing.

Since I can vividly and clearly conceive mind and body as distinct, they must actually distinct

Divisibility Argument

Thinker: Descartes

1. All bodies are divisible

2. I am not divisible

3. Therefore I am distinct from my body

Anything extended can be divided into parts

Mind is indivisible

Princess Elisabeth’s Criticism of Descarte’s Substance Dualism

Thinker: Princess Elisabeth

Interaction Problem: If the mind is non-extended and the body is extended, how can the mind cause the body to move?

• Descartes’ response: Weight analogy

  • Concept exists of weight as a force that compels things to move to center of Earth without physical contact

  • Mind-body don’t need to interact like body-body

• Elisabeth’s response

  • Accepts that the mind and body do interact

  • Still doesn’t answer how the interaction occurs

  • Maybe the soul isn’t actually non-physical

Overdetermination

Thinker: Papineau

An effect has two distinct causes that each can cause the effect independently

Dualist response: “Belt and Braces” view

• Mental and physical causes are both real and behavior is overdetermined

• Basically allowing overdetermination

Papineau’s criticism

• This would mean the effect can still occur if one cause was absent

• If both causes are actually required, then are they really distinct?

• Not found in nature

Causal Closure Argument

Thinker: Papineau

1. Consciousness has physical effects

2. All physical effects have fully physical cause

3. Physical effects of conscious causes aren’t always overdetermined

Therefore conscious cause and physical cause must be identical, thus physicalism is true.

Causal Danglers

Thinker: Papineau

Criticism of epiphenomenalism

• Leaves conscious states as “danglers” since they are caused, but do no causal work itself

• Unintuitive to say your feelings don’t cause anything

• Less parsimonious

Body Problem

Thinker: Montero

Most discussion is about if mind is physical, but what does “physical” actually mean?

Similarity to accepted cases?

• We know things like a rock and table are physical

• Problem: difficult to measure “similarity” for something like a belief or a lepton

Excluding what it’s not?

• Exclude things we know are non-physical like ghosts, souls, etc

• Problem: what specific features/properties distinguish these?

Shared properties?

• Physical things all made of the same stuff, so non-physical things won’t be

• Problem: what if we discover a new particle?

“Physical” is cannot be defined, so we can’t solve the Body Problem, thus we can’t rely on “physical” for other arguments.

Hempel’s Dilemma

Thinker: Used by Montero

Suppose we define “physical” in terms of physics.

Current physics

• Whatever current physics says exists

• Problem: current physics is prob incomplete/inaccurate

Future physics

• Whatever a complete/final physics says exists

• Problem: we don’t know what that is, definition becomes vague

Neither option works, so physicalism seems impossible

Mark of the Mental

Thinker: Montero

We should reframe the Body Problem: Is the mental state non-mental fundamentally?

• Can the mental state be broken down in terms of non-mental things?

• Avoid talking about if mind is physical, since “physical” is unclear

Synchronic vs. Diachronic Awareness

Synchronic - consciousness at a particular point in time

Diachronic - consciousness across time