The options The mind is not the brain: it is a different thing, i.e. it can exist on its own without the brain (e.g. after death). (Substance dualism) The mind is the brain: they are completely identical. (Materialism/physicalism) The mind depends on the brain to exist: mental properties are properties of the brain, but they are not physical properties. (Property dualism)
Substances and properties Substances can have different sorts of properties Reductive physicalism: mental properties are physical properties Property dualism: mental properties are not physical properties Hmm…
Arguments for substance dualism Religious teachings Different essential properties –Descartes: The body essentially has parts, the mind has no parts. So they are different kinds of thing. Descartes’ argument from knowledge
Descartes’ argument 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.
Objection 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. If ‘two’ things have different properties, then they really are distinct. But we can be mistaken about the properties of things. Perhaps there is a metaphysical connection between mind and body that Descartes doesn’t know about.
Parts and properties The argument that mind has parts assumes that minds exist as things that have properties. Materialists reject this – minds don’t exist, only mental properties (of brains) do.
The challenge of mental causation Descartes: mind and body are different kinds of thing. The mind is just thought, not in space; the body, matter, is just extension, in space. So 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.
Mind-brain identity Ontological reduction: the things in one domain (e.g. mental things) are identical with some of the things in another domain. Reduction: this makes the ‘reduced’ domain more intelligible If mind = brain, then mental causation doesn’t violate of laws of physics and we can understand how it happens (usual physical way).
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
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 H 2 O).