Multiple Realizability, Qualia and Natural Kinds

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Multiple Realizability, Qualia and Natural Kinds
4) The property-level account of MR Multiple
realizability has often been taken to be a
relation among properties at different levels,
whereby a higher-level property is multiply
realizable if it can be realized by more than one
lower-level property. This has as a consequence
(or a presupposition) the ontological position
that the world is layered. Reality comprises
levels of objects, properties, and laws (Heil
1999, 189).
6) The determinable/determinate account of MR
1) What is a natural kind?
Natural kinds are groups of objects that have
some theoretically significant property, or
properties, in common. These properties are
significant because an objects membership of a
given natural kind determines how that object
will behave. Thus, natural kinds can form a
system that supports the explanation and
prediction of the behaviour of those objects,
including inference to counterfactual cases.
Common examples of natural kinds include
biological species, chemical elements and
compounds, and stuffs, such as salt, wool and
heat in a gas.
A) A mental property is to its physical
realizations as a determinable, like redness, is
to its determinates, such as scarlet or
crimson. B) Determinables are not genuine
properties determinates are properties.
Determinable predicates are satisfied by ranges
of sufficiently similar properties
(determinates). On this model, we can say that
the predicate is in pain, though it holds of
particular objects at particular times, and does
so in virtue of their properties, nevertheless
does not itself designate a property. C) This is
not a form of anti-realism or anti-naturalism
about determinables the predicate is in pain can
still be employed in theoretically fruitful
generalizations, even generalizations that would
remain invisible at lower levels of abstraction,
and can be projectible in a lawlike way where
this ceteris paribus lawlikeness is grounded in
the similarity of causal powers picked out by the
predicate.

• 5) A problem for the property-level account (from
  Heil 1999)
• If some higher-level propertypain, sayis
  realized in a human being by pyramidal cell
  activity, then it seems that two properties are
  being tokened at the same time there is the
  property of being pca but there is also the
  distinct property of being a pain.
• Why should we suppose that the higher-level
  property, in each of its tokenings, is distinct
  from the lower-level property that realizes it on
  that occasion? Standardly, because we hold that
  the special sciences are autonomous they capture
  laws and generalizations that are not replaceable
  by those of lower-level sciences. It follows that
  properties are individuated by their
  contributions to the causal powers of objects
  instantiating them two properties differ iff
  they feature in different sets of scientific
  laws.
• But this view is untenable. Consider a
  higher-level property M and three lower-level
  realizers, N1 N2 and N3
• If M has a subset of the causal powers of N1 then
  it is unclear what more there is to the objects
  possessing M than its possessing N1. If M has a
  subset of causal powers held in common between N1
  N2 and N3 then M is identical with the physical
  property defined by these causal powers (and so
  is not multiply realizable).
• If M has a superset of the causal powers of N1
  then it is mysterious where the additional causal
  powers come from.
• If M has the same set of causal powers as N1 then
  it is identical with it (and so is not multiply
  realizable).

2) Why is multiple realizability a problem for
natural kindhood? Its a problem because it
seems to show that the similarities among certain
manifest kindssuch as pain, desiring p, being
a flying thing, or being jadeare not supported
by underlying, scientifically interesting
commonalities. Chemical compounds and biological
species are natural kinds in virtue of their
underlying, empirically discovered natures (their
chemical composition or, perhaps, their shared
evolutionary history). It is these natures that
underpin inductive generalizations over the
members of those kinds. If water had turned out
to be one chemical compound in the Pacific,
another in the Atlantic, another in the Great
Lakes, and so on, then it would not have been a
natural kind. In the same way there is no
single neural kind N that realizes pain, across
all types of organisms or physical systems
rather, there is a multiplicity of
neural-physical kinds, Nh, Nr, Nm, such that Nh
realizes pain in humans, Nr realizes pain in
reptiles, Nm realizes pain in Martians, etc.
(Kim 1992, 5).

• 7) Results
• MR does not provide any additional difficulties
  for considering phenomenal kinds to be as good
  candidates for natural kindhoodand hence a sort
  of scientific respectabilityas any other species
  of high-level property.
• Phenomenal properties, though multiply
  realizable, need not be epiphenomenal tokenings
  of determinate pains can have causal powers,
  consistently with there being no one set of
  causal powers that is definitive of pain. The
  determinable/determinate account of MR provides a
  nonad hoc solution to the causal problem of
  consciousness.
• The kind of similarity that is relevant for
  phenomenal kinds is phenomenal similarity.
  Nothing in the determinable/determinate account
  of MR requires that the similarity between
  determinates, in virtue of which they are all
  versions of the same determinable, be causal,
  even though the identity conditions for
  properties (determinates) involve causal powers.
  However it is an interesting question whether the
  structure of the space of phenomenal similarity
  must be isomorphic with the structure of the
  physical similarity-relations otherwise how are
  the phenomenal relations to be explained?
• It follows from this account of MR that two
  identical determinate pains must have relevantly
  the same physical instantiations (since they will
  be identical in causal powers). So for
  determinate pains a kind of mind-brain identity
  theory is entailed, consistently with the facts
  of multiple realizability.

3) What are qualia? I am treating qualia, not as
functional kinds, but as phenomenal kinds,
realized by the brain. On this view pain, for
example, is best thought ofalbeit looselyas a
kind of stuff, like heat or salt, whose
essential micro-properties explain both its
macro-properties and its lawlike relations to
other entities. Although on the one hand multiple
realizability is prima facie a more pronounced
phenomenon for functional properties than for
phenomenal ones, on the other the functionalist
response to the multiple realizability threat to
natural kindhood is not available to us.
Dr. Andrew Bailey Philosophy Department University
of Guelph Guelph, Ontario N1G 2W1,
Canada abailey_at_uoguelph.ca www.uoguelph.ca/abaile
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References Heil, John (1999). Multiple
Realizability, American Philosophical Quarterly
36. 189208. Kim, Jaegwon (1992). Multiple
Realizability and the Metaphysics of Reduction,
Philosophy and Phenomenological Research 52.
126. Robb, David (1997). The Properties of
Mental Causation, The Philosophical Quarterly
47. 178194. Yablo, Stephen (1992). Mental
Causation, Philosophical Review 101. 245280.