Substance and Property Dualism

1. Substance and Property Dualism Michael Lacewing enquiries@alevelphilosophy.co.uk

2. Metaphysics of mind • Substance: needs no other thing to exist • Dualism: there are two sorts of substance, mind (or soul) and matter • Mental properties are properties of a mental substance • Materialism: there is just one sort of thing, matter • Mental properties are properties of a material substance

3. Materialism and mental properties • Substances can have different sorts of properties • Biological: swan • Colour: white • But both physical properties • Property dualism: mental properties are not physical properties Hmm…

4. Descartes’ dualism • The mind is a separate substance from the body. • What am I? I am a thing that thinks. I cannot doubt this, yet I can doubt whether I have a body. So I can be separated from a body. • The body has parts, the mind has no parts. So they are different kinds of thing.

5. Objections • Descartes has not shown that he (the mind) is a substance. • Just because Descartes can think of his mind existing without his body, this doesn’t mean that his mind really can exist without his body. • Cp. I think the Masked Man robbed the bank; I don’t think my father robbed the bank; Therefore, my father isn’t the Masked Man. • We can’t infer real possibility directly from what we can imagine.

6. Mental causation • If the mind is just thought, not in space, and matter is just extension, in space, how could one possibly causally affect the other? • All physical effects have a sufficient physical cause. Nothing physical happens needs a non-physical explanation. • Mental causes would violate the laws of physics, e.g. law of conservation of energy.

7. Jackson’s knowledge argument • Mary, a neuroscientist, has never seen colour, but knows all about colour perception • Mary doesn’t know what it is like to see red - so, although Mary knows all the physical facts about seeing red, there is a fact (of consciousness) Mary doesn’t know • Therefore, properties of consciousness are not physical properties

8. Reply • Mary doesn’t learn a new fact, but a new way of thinking about an old fact. She now knows the fact of what happens in the brain through introspection. • On concepts and properties: the same fact (the glass contains water) can be thought of in different ways (the glass contains H2O).

9. Zombies • Zombie (in philosophy, not voodoo!): a physical replica of a person, but without consciousness • A zombie has identical physical properties, but different mental properties - therefore mental properties aren’t physical properties • Zombies may not be physically possible, but they are logically possible

10. Reply • Zombies are not possible - that we can imagine them isn’t enough (see objection to Descartes) • Imagine that water is not H2O - it seems we can, but in fact, this is impossible • There could be something just like water, but if it isn’t H2O, it isn’t water

11. Response • The analogy doesn’t work • We make the mistake in the case of water, because we imagine something just like water • There is nothing ‘just like’ a zombie which isn’t a zombie • Imagination is a good guide to possibility here - therefore zombies are possible, and property dualism is true