Dualism

Interactionism

The physical and mental cause each other. They interact.

Epiphenomenalism

The physical causes the mental. The mental has no causal role.

Property dualism

The view that there is one kind of substance (physical), but it has both physical and non-physical (mental) properties that are not reducible.

Substance dualism

The view that there are two distinct substances, physical (body) and non-physical (mind), which exist independently.

Problem of other minds

Dualism claims mental states are private and not directly observable, so we only see behaviour. Therefore we cannot be certain others have minds, leading to solipsism.

Argument from analogy

We know our own mental states cause our behaviour, and others behave similarly so we infer by analogy that they have similar mental states.

Best hypothesis response

Dualists can claim the best explanation of behaviour is that others have minds like ours. Alternative explanations fail, but this is not logically provable.

Category mistake

Substance dualism claims the mind is a separate substance alongside the body. Ryle argues this is a category mistake, as the mind is just behaviour and dispositions.

Conceptual interaction problem

Interactionist substance dualism claims the non-physical mind causally interacts with the body. But a non-extended mind cannot make contact, so interaction seems impossible.

Empirical interaction problem

Interactionist dualism claims mental events can cause physical events. But a non-physical mind cannot transfer energy, so this conflicts with conservation of energy.

Introspective self-knowledge

Epiphenomenalism claims mental states have no causal power, yet we voice them. This suggests mental states cause behaviour, so self-knowledge of mental states doesn’t make sense.

Phenomenology of mental life

Epiphenomenalism claims mental states do not cause anything. But our experience suggests mental states cause actions and other mental states.

Natural selection and evolution

Epiphenomenalism claims mental states have no causal role. But evolution only selects traits that affect behaviour, so consciousness becomes hard to explain.

Substance Dualism

The view that there are two fundamentally different types of substance: physical substances or bodies and mental substances, or minds.

Substance

Something that does not depend on another thing in order to exist, which possesses properties and persists through changes. 

Property

An attribute or characteristic of a substance. Depends on the substance in order to exist.  

Indivisibility Argument

• P1. It is a law of logic that if x and y have exactly the same properties then x=y  

• P2. If there is a property P that x has but that y does not have then x is not numerically identical to y.  

• P3. My body is always divisible.  

• P4. My mind is always indivisible.  

• C1. Therefore, my body cannot be the same substance as my mind.  

The mental is divisible in some sense

Modern neuroscience shows brain damage can impair parts of the mind, effectively dividing it. There is also split-brain surgery and multiple personality disorder which show a division of consciousness. 

Not everything thought of as physical is divisible

Things like elementary particles like atoms, or electromagnetic fields aren’t legitimately divisible, yet they’re physical. 

The conceivability argument

• P1. If I can clearly and distinctly recognise the nature of two things to be different then they are different   

• P2. I can conceive (clearly and distinctly recognise) that my mind, a thinking non-extended thing, can exist without my physical non-thinking extended body existing.   

• C1. Therefore it is metaphysically possible for my mind to exist without a body.   

• P3. If it is metaphysically possible that X exists without Y, then Xand Y are not identical.   

• C2. Therefore, my mind is not identical with my extended body.   

Mind without body is not conceivable

The separation of mind and body is only apparently conceivable, not genuinely. Clear and distinct conceivability requires full understanding, which we lack regarding the nature of the mind.

What is conceivable may not be metaphysically possible

Just because we can imagine something doesn’t mean it could really exist. One might conceive of a right-angled triangle without a hypotenuse but that’s impossible once we know Pythagoras' theorem. It was conceived before it was understood, therefore, conceivability doesn’t guarantee metaphysical possibility.

What is metaphysically possible tells us nothing about the actual world

Even if minds without bodies are metaphysically possible, that doesn’t prove they actually exist. It’s possible unicorns could exist, but that doesn’t mean they do.

Supervenience

X supervenes on Y if and only if a change in Y is necessary for a corresponding change in X to be possible. 

The philosophical zombies argument

P1: It is possible to conceive of a zombie.

P2: A zombie is physically identical to a human, but without the mental property of consciousness.

P3: Conceivability implies the idea that it is metaphysically possible.

P4: Consciousness is a mental property.

P5: If a physical brain without consciousness is conceivable, then consciousness must be separate from the physical.

C: Therefore, property dualism is true.

A zombie world is not conceivable

If consciousness relies on the physical processes in our brain, then a 'zombie' physically identical to a human must have consciousness. We can only conceive of it because we don’t understand it.

What is conceivable may not be metaphysically possible

Just because we can imagine something doesn’t mean it could really exist. One might conceive of a right-angled triangle without a hypotenuse but that’s impossible once we know Pythagoras' theorem. It was conceived before it was understood, therefore, conceivability doesn’t guarantee metaphysical possibility.  

What is metaphysically possible tells us nothing about the actual world

Even if a zombie world is metaphysically possible, that doesn’t prove that it is actually true of our world. It’s possible unicorns could exist, but that doesn’t mean they do, and it doesn't mean they're relevant to the real world.

The Mary argument

P1: Someone who knows everything physical about colour without seeing it would have 100% physical knowledge.

P2: Upon seeing colour for the first time, they would gain knowledge.

P3: This cannot be physical knowledge since they already have 100% of this.

C: Therefore, there is non-physical knowledge, and physicalism is false.

Mary gains ability knowledge (objection)

When Mary leaves her black-and-white room and sees colour, she gains no new propositional knowledge. Instead, she gains new ability knowledge: the ability to recognise or imagine red, the ability to remember red, the ability to compare shades of red

Mary gains acquaintance knowledge (objection)

When Mary sees colour for the first time, she becomes acquainted with a new property: the qualia of seeing red.

Mary finds a new way to know her knowledge

Mary just comes to know her physical knowledge under a new mode of presentation. She already knew all the physical facts about colour vision, but lacked the qualia to represent them from the first-person perspective.

Property Dualism

At least some mental properties are not reducible to, nor dependent on, physical properties.

Example of supervenience

A painting’s beauty cannot change without a corresponding change in the physical arrangement of paint or light.

Property dualism against supervenience (mental on physical)

Mental states could change without any change in the brain. Therefore, two physically identical brains could have different mental states

Philosophical zombies

Beings physically identical to humans but with no consciousness.

Key claim of the zombie argument

If zombies are conceivable, consciousness must non-physical.

Key claim of the Mary argument

Physicalism is false because Mary learns something non-physical when she sees colour.