thesis

understanding as would colours to a person who could only see in shades of grey. There
seems to be no reason why outsiders need necessarily realise we are more conscious than vi-
ruses, bacteria or plants, if indeed we are.
Alternative Positions
What are the body and the mind made out of? Five standard positions may be enumer-
ated – materialism, idealism, neutral monism, property dualism and substance dualism.
Each of materialism, idealism and neutral monism is a variation on the notion that there is
only one type of substance and property. In the case of materialism, the nature of this one
substance and its properties are material in the sense in which that is currently understood –
describable in terms of mass, energy, space, time and fields – any mental processes take
place only within this realm. Idealism adopts the opposite view in claiming that the single
substance is made out of thoughts or concepts – any apparent material processes are a result
of the interaction of these ideas. Lying between materialism and idealism, neutral monism
holds that there is only one type of substance and property, yet the precise nature of this is
either epistemically inaccessible or at least not yet understood.
By contrast, property and substance dualism hold that there are two types of properties
in the cosmos. While property dualism attributes these both to a single substance (and is
thus close to but not identical with neutral monism), substance dualism attributes them to
two different types of substance, the mental/spiritual and the material/physical. While sub-
stance dualism remains the mainstay of theistic metaphysics, property dualism is often seen
as a way to hold onto physicalism while taking the phenomenon of consciousness seriously.
Chalmers sees himself largely in the property-dualist vein.
Under either property or substance dualism, there are further issues concerning the in-
teraction between the two properties or substances. Do mental properties or substances have
any effect on material ones? If not, we have a case of strong epiphenomenalism, where nothing
about the physical world is affected by what takes place in conscious minds. And if so, can
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