The mind-body problem has posed the questions: can we defend mental
causation, or is there causal relevance of mental qua mental over and above
physical in human behaviour? This would mean that conscious experience is
not a physical phenomenon, though it has causal relevance in the world. The
problem is understanding how something non-physical, mental or phenomenal
could be causally relevant in a physical world. Physicalists and scientists
have defended the plausibility of a principle that states the causal closure
of the physical domain. This is the claim that the physical is closed off to
all causal influences of non-physical events and non-physical properties. In
conflict with that is what we think of mental states and properties of our
consciousness as causally relevant to our behaviour and causally efficient
in the physical world. If the physical closure principle stands, and only
physical causation is possible, then mental causation in dualism is
impossible, as is the usual argument against dualism. But we can also find
this principle of physical causal closure in Russellian panpsychism.
Russellian panpsychism and similar positions have come about as answers to
the mental causation worries of physicalism and dualism. Panpsychism has the
advantages of both positions. Science can only tell us about the relational
or extrinsic (structural) properties, but mental states? phenomenal
properties are intrinsic. These intrinsic properties can be the causal bases
for extrinsic properties (or dispositions) and determine them. This is also
the distinction between dispositional and categorical properties. If there
is more to nature than relational properties, if there are some categorical
bases of dispositions, then all causal explanations cannot be stated only in
physical terms and just with mention of physical properties. Science (and
physicalism) does not know anything beyond dispositions and structure, but
there is great plausibility in the claim that dispositions have causal bases
and are not groundless. The bases of dispositions are categorical intrinsic
properties; the only absolutely intrinsic properties we know (intimately)
are phenomenal properties of our conscious states. This means that the
causal closure principle is false.