Greg Detre
Monday, May 22, 2000
forthcoming in �New Essays on the A Priori�, edited by Paul Boghossian and Christopher Peacocke, and published by Oxford University Press)
subjective phenomenological features of conscious experience are perfectly real and non-reducible
but their systematic relations to neurophysiology are not contingent, but necessary
functionalism = theories that identify mental states by their typical causal roles in the production of behaviour (aka their �functional roles�)
not the version of functionalism that identifies mental states with computational states
functionalism always suffers the same problem:
however
complete an account may be of the functional role of the perception of the
color red in the explanation of behavior, for example, such an account taken by
itself will have nothing to say about the specific subjective quality of the
visual experience, without which it would not be a conscious experience at all.
exploring an anti-functionalist alternative to Saul Kripke�s challenge:
That the usual moves and analogies are not
available to solve the problems of the identity theorist is, of course, no
proof that no moves are available....I suspect, however, that the present
considerations tell heavily against the usual forms of materialism.
Materialism, I think, must hold that a physical description of the world is a
complete description of it, that any mental facts are �ontologically dependent�
on physical facts in the straightforward sense of following from them by
necessity. No identity theorist seems to me to have made a convincing argument
against the intuitive view that this is not the case.
materialism has to defend the very strong reductionist claim that:
mental phenomena are strictly necessary
consequences of the operation of the brain -- and that the defense of this
claim lies under the heavy burden of overcoming the prima facie modal argument
that consciousness and brain states are only contingently related, since it seems
perfectly conceivable about any brain state that it should exist exactly as it
is, physically, without any accompanying consciousness
it seems
that there need be no necessary connection between phenomenological
consciousness and physical brain processes � this is what Nagel wants to
challenge
make sense of: mental processes are physical
processes necessarily but not analytically
not materialism/physicalism: a physical description of the world is a
complete description of it
but there may be other forms of noncontingent psychophysical identity
assumptions + truths:
the semantic category of analytic or conceptual
truths, the epistemological category of a priori truths, and the metaphysical
category of necessary truths do not coincide -- nor do their complements:
synthetic, a posteriori, and contingent truths.
conceptual truths = the properties by which we fix the term
theoretical truths = derivable from laws in physics/chemistry (= necessary consequences of premises with are partly necessary, partly contingent � the nature of hydrogen and water)
a posterior conclusion = from evidence of the manifest properties of water
necessary truth = even
though discovered a posteriori, because if it is true then any other substance
with the same manifest properties which did not consist of H2O would not be
water
conceptual
truth = this last conditional clause, following �because,� is a conceptual
truth, discoverable by reflection on what we would say if....
functionalism = the
claim that it is a conceptual truth that any creature is conscious, and is the
subject of various mental states, if and only if it satisfies certain purely
structural conditions of the causal organization of its behavior and
interaction with the environment -- whatever may be the material in which that
organization is physically (or nonphysically) realized
As I have said, I do not believe that this is a conceptual truth, because I do not believe that the conceptual implication from functional organization to consciousness holds.
I don�t doubt that all the appropriately behaved and functionally organized creatures around us are conscious, but that is something we know on the basis of evidence, not on the basis of conceptual analysis.
conceptual connection between conciousness + behavioural/functional organisation
but only in one direction (i.e. consciousness gives rise to behavioural/functional organisation???)
Finally, and this is the main point, while it
is obviously not conceptually necessary that conscious mental states are tied
to specific neurophysiological states, I contend that there are such
connections and that they hold necessarily. They are not conceptual, and they
are not discoverable a priori, but they are not contingent. They belong, in
other words, to the category of a posteriori necessary truths. To explain how,
and to characterize the type of necessity that could hold in such a case, is
the problem.
i.e. given certain only-partly-necessary premises, discoverable only a
posteriori, they are necessarily so
if the psychophysical identity is to be an empirical reduction or theoretical identification (like heat to molecular motion, or fire to oxidation), then it cannot be a contingent proposition
the terms of such an identity are both rigid designators � they apply (or fail to apply) to the same things in all possible worlds
Kripke observes that there is an appearance of
contingency even in the standard cases of theoretical identity. The
identification of heat with molecular motion is not analytic, and it cannot be
known a priori. It may seem that we can easily conceive of a situation in which
there is heat without molecular motion, or molecular motion without heat. But
Kripke points out that this is a subtle mistake. When one thinks one is
imagining heat without molecular motion, one is really imagining the feeling of
heat being produced by something other than molecular motion. But that would
not be heat � it would merely be a situation epistemically indistinguishable
from the perception of heat. �Heat,� being a rigid designator, refers to the actual
physical phenomenon that is in fact responsible for all the manifestations on
the basis of which we apply the concept in the world as it is. The term refers
to that physical phenomenon and to no other, even in imagined situations where
something else is responsible for similar appearances and sensations. This is
so because the appearances and sensations of heat are not themselves heat, and
can be imagined to exist without it.
does the same apply for �consciousness�, rather than heat?
no � there is no way to merely imagine the appearance of the experience
without the experience itself
i.e. apparent consciousness is consciousness
We identify experiences not by their contingent
effects on us, but by their intrinsic phenomenological qualities
So if they are really identical with physical
processes in the brain, the vivid appearance that we can clearly conceive of
the qualities without the brain processes, and vice versa, must be shown to be
erroneous in some other way.
Nagel is trying to show that this can be done:
If the appearance of contingency in the
mind-body relation can be shown to be illusory, or if it can be shown how it
might be illusory, then the modal argument against some sort of identification
will no longer present an immovable obstacle to the empirical hypothesis that
mental processes are brain processes.
an identity must demonstrate that all the properties manifest are entailed by the scientific description
this �upward entailment� is so difficult to imagine in the case of brain states � phenomenological experience
it seems that no amount of information about the spatiotemporal order will entail anything of a subjective, phenomenological character
= a totally different logical type
\ there can be no reduction
difference between semantic conceptual truths and metaphysical necessary truths
e.g. identity of heat with molecular motion or of water with H20
modal argument
modal = designating or pertaining to a proposition
involving the affirmation of possibility, impossibility, necessity, or
contingency, or in which the predicate is affirmed or denied of the subject
with a qualification; (of an argument) containing a modal proposition as a
premiss.