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?