The
Explanatory Argument
David
Chalmers says that the “easy problems” of consciousness explain
“only structure and function”. They don't explain consciousness. Therefore “no physical account
can explain consciousness”.
The
Conceivability Argument
We
can conceive of a
physical system that is note-for-note identical to us but which
doesn't have consciousness. (Though what has the psychological notion
of conceivability got
to do with the problem of consciousness?)
Such
as system would therefore be a zombie. Alternatively, it may be a
zombie-invert in that some of its experiences are inversions of those
of human beings.
The
invert-zombie has the same nuts and bolts as us; though nevertheless it has
different experiences. So the inverted zombie is still allowed his
experiences.
There
is also the conceivability of a partial zombie who also has
experiences; though not as many as those of human beings – perhaps
he can only feel pain.
The
point is that all these zombies are physically identical to us from
the third-person point of view and their behaviour will also be
indistinguishable.
What
about their first-person point of view? What is it like to be a
zombie of whatever kind? Well, there's nothing it is like to be a
bona fide zombie!
On
a larger scale. What about a physically identical universe that
doesn't, however, give rise to consciousness; though which does give
rise to zombies? We can say that such zombies are indeed "naturally
possible". However, according to our laws of nature, they probably
couldn't exist. That is, given identical physical and bodily facts,
then such a universe couldn't help but give rise to consciousness.
(This is what some non-reductive physicalists and supervenience
theorists believe.)
Let’s
take this further.
There
could be an identical universe that didn't give birth to
consciousness. If this were the case, then consciousness must be
something above and beyond the physical if such a counterfactual
scenario were possible. In addition, if we can conceive of such
zombies in our world or at other worlds, then Chalmers claims that it is "metaphysically possible" that there could be zombies.
What
does metaphysical possibility add to the notion of
conceivability?Chalmers codifies and simplifies this with a
logical argument:
i) It is conceivable that P & not-Q.
ii) If it is conceivable that P & not-Q, then it is metaphysically possible that P and not-Q.
iii) If it is metaphysically possible that P & not-Q, then materialism is false.
iv) So materialism is false.
(Can
a mere possibility make materialism false?)
Again,
we can see Chalmers’ slide from conceivability to metaphysical
possibility. Why should it be that simply because we can conceive of
something then that something is metaphysically possible? This has an
almost empiricist ring to it in that all conceivables (or ‘ideas’)
must come from somewhere or entail metaphysical
possibility.
Can
we conceive a round square? No. Then it isn't metaphysically
possible. Can we imagine a man with five legs? Yes. Then it's
metaphysically possible.
The
Knowledge Argument
To
put the case simply. We could never, and have never, deduced or
inferred consciousness from the sum of all physical facts. Though, then
again, the same can be said about water. We could study H2 O until
the cows come home; though we would never deduce (or infer) the reality
of water - its wetness and drinkability - from such physical facts.
We can only do so a posteriori – in this case, through
science, which tells us that water is indeed H2 O. Though no scientist
has ever (or could ever) infer or deduce water’s wetness, etc. a
priori. (Or could they? Is water’s transparency an emergent
property?)
Does
Mary lack knowledge about red? She obviously lacks the experience of
red. Is the experience of red a ‘fact’? What sort of fact would
it be? Frank Jackson argues that if she finally came to actually
experience red, she would learn a ‘new fact’ about red which must
be over and above her knowledge of its physical basis and even beyond
her powers of deduction from such facts. That is, experience emerges
from the physical; though it can't be read off from the physical.
That is the essence of emergentism.
Jackson
concludes that Mary does indeed know all the physical facts; though
not all the facts. There must be non-physical facts (one of which is
consciousness).
The
strong conclusion to all this is that i) If there are more than physical facts
ii) and that these things can't be deduced from physical facts
iii) then materialism must be false.
That's because materialism only allows physical
facts in its world-picture.
The
Shape of the Arguments
Chalmers
then attempts to codify and simplify the arguments in strictly
logical terms.
Firstly
we can think in terms of epistemic entailment, deducibility,
explicability and conceivability.
Let
us take epistemic entailment.
This
is a priori entailment or implication in that it doesn't
depend on (further) experience. If we have
P ⊃ Q
we
have a material conditional from the physical facts to an arbitrary
phenomenal fact. When we know that P is the case, then we must
also know that Q is the case without further experience.
In
the case of consciousness, P doesn't entail or imply Q a
priori. We can't deduce Q from P. Similarly, we can
conceive of P without thereby also conceiving of Q. Or, in
functional terms, if P is functional, then we can't deduce Q
from P because consciousness “is not a functional concept”
(as we saw earlier in this debate).
These
logical uses of the material conditional can also be applied to the
conceivability argument, the knowledge argument and the explanatory
argument.
Taken
one by one.
If
we can conceive of zombies, then zombies are metaphysically possible.
If we can't deduce consciousness from all the physical facts, then
some facts - those of consciousness - aren't physical. If physical
explanations aren't adequate, then there must be non-physical facts
that require non-physical explanations.
Now
we can talk of another kind of entailment: ontological
necessitation.
We
can say that P necessitates Q. In the material conditional P
⊃ Q, we can say that P can't hold without
necessitating Q. It is ontologically necessary that P
necessitates or entails Q. Again, if this were the case, then
materialism would be false.
The
other interesting point about these arguments is the movement from an
epistemic gap to an ontological gap. More precisely, we can argue
that:
- There is an epistemic gap between physical and phenomenal truths.
- If there is an epistemic gap between physical and phenomenal truths, then there is an ontological gap, and materialism is false.
- Materialism is false.
The obvious point to make here is the slide from the epistemic gap to an ontological gap. What does that mean?
If
we can't slide from our knowledge of P to Q, then that
must be because P and Q are ontologically different. If
P and Q were ontologically of the same order, then we
could move, epistemically, from P to Q.
Why
does a lack of epistemic movement from P to Q entail
ontological difference? Couldn’t that epistemic gap be accounted
for simply in terms of our epistemic limitations or our inadequate knowledge or physical devices? We at one time couldn't move from H2
O to the wetness of water. That epistemic or scientific gap didn’t
engender an ontological difference between H2 0 and water or even
water’s wetness. Does a lack of knowledge about X entail
the fact that X is ontologically weird or irreducible?
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