person = 1 body (matter) + 1 mind (mind-stuff) in causal interaction
two initial worries about this view: (1) if mind-stuff has no
mass, shape, or location, how does it get the body to do things?
(2) anyway, the essential feature of matter does not seem to be extension
(nonphysical = cannot be reduced to or explained in terms of physical properties)
[Bracketed comments are mine -- CB: One way to think about this is to think of mental properties, on the property dualist account, as extra properties in some sense. For instance, imagine what it would be like if color turned out to be an extra property. It could be that only certain kinds of objects have colors, but it could have turned out that color had no relation to microphysical properties -- that color could differ even between physical duplicates.
there are many properties which it is not straightforward to define in terms of physical properties, but which we nevertheless do not think are extra in this sense: e.g. smiling, being worth $3, being alive, being yellow, being a chair. The property dualist thinks that mental properties are extra in a sense in which these are not.]
A. Epiphenomenalist property dualismmental properties are caused by physical properties, but have no causal effects in turn (the mental as superfluous)
reason for the view: (a) firm conviction that mental properties are irreducible to physical ones, with (b) firm conviction that physical causes suffice to cause physical behavior. If both (a) and (b) are held to, epiphenomenalism is the only option
but notice how persuasive (b) is: to invoke nonphysical properties seems to be a way of giving up the search for an explanation.
B. Interactionist property dualismmental and physical properties interact causally
mental properties are (a) emergent and (b) irreducible.
But these two features fit oddly together; seems it would be better to give up one.
If you give up (a), you are a panpsychist; if you give up (b), you are a materialist.
2. explanatory impotence of dualism: we know a lot about matter and its relation to consciousness; we know nothing about mind-stuff
3. argument from the neural dependence of all known mental phenomena
4. argument from evolutionary history