© Michael Lacewing Dualism and the Mind-Body Identity Theory Michael Lacewing

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

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.

Objections 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. Perhaps there is some metaphysical connection between his mind and body that would make this impossible that Descartes doesn’t know about. 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.

Materialism and mental properties Substances can have different sorts of properties Property dualism: mental properties are not physical properties Type identity theory: mental properties are physical properties Hmm…

Mental causation Causation requires things to ‘happen’. ‘Things happening’ are events. A cause and its effect are both events, changes at a time (or over time) in the properties of objects. Like picking up the remote control

The problem for dualism 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.

Mind-body identity and reduction 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 = body, then mental causation doesn’t violate of laws of physics and we can understand how it happens (usually physical way).

Multiple realizability Mental properties cannot be identical to physical properties because the same mental property can be ‘realized by’ different physical properties, e.g. the brain states that relate to pain are different in different species, but pain is the same mental state.