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Knowledge Mind & Language
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Contents |
We are going to explore the idea that the brain is a computer.
Fred Jackson's paper 'Epiphenomenal qualia' articulates some arguments to back up the strong intuition that some of us have that conscious experience cannot be identified with physical processes. At the core of his article are a couple of scenarios.
FRED IS A PERSON WHO SEES AN EXTRA COLOUR COMPARED WITH THE REST OF US.
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Web stuff with its directory of online papers on Philosophy of Mind topics Dictionary of the Philosophy of Mind courtesy Chris Eliasmith |
Give Fred a pile of ripe tomatoes which you and I would say are all exactly the same colour and Fred sorts them into two piles. He says that he has sorted them by colour. The colour of the tomatoes in pile 1 is different he says from the colour of the tomatoes in pile 2.
You blindfold him, shuffle the tomatoes up, take the blindfold off, get him to sort them by colour again, and he makes exactly the same piles as before.
He can do this repeatedly, with perfect consistency, without difficulty.
We ask him how he does it and the reply is that all the tomatoes do not appear the same colour to him. He sees two colours.
He has special words he uses himself to mark this distinction. Some of the tomatoes are red(1) and some are red(2). But he explains these two are not shades of the same colour. They are as different from each other as say yellow is from blue. His ability to sort the tomatoes into the two categories bears this out: he always does so without the least apparent difficulty, in all sorts of light, without ever making mistakes.
When
a physiological investigation is made into this extraordinary ability, the following
is found:
Associated with the ordinary red is a cluster of wavelengths. Fred's red(1) is associated with a subset of these, and his red(2) is associated with the rest. I.e. we say 'red' when we are responding to wavelengths 10 to 20, say: his red(1) corresponds with 10 to 15, and his red(2) with 16 to 20.
Jackson says we should conclude from these facts that Fred can see one more colour than we can.
Pause: is that agreed? What more clarification do you need before agreeing?
Jackson then asks the crucial question.
We would like to know what the special colour is like. 'What kind of experience does Fred have when he sees red(1) and then red(2)?'
This is a sensible question, says Jackson, and it is one we would probably be keenly interested to have answered.
The crunch however is this: 'no amount of physical information about Fred's brain and optical system' can possibly provide the answer for us. Jackson, Reader, p.470.
We may suppose we know everything about Fred's body
- everything about his behaviour
- everything about dispositions to behave
- everything about his physiology
- everything about his history
- everything about his relations to others
We may have all this, all the physical information that there is. But none of this, nor the whole of it, tells us what the special colour is like, what Fred's experience is when he looks at the two categories of tomatoes, one after the other.
It follows, says Jackson, that what he calls 'physicalism', of which the identity theory is a form, 'leaves something out' .
To drive the point home, as he thinks, Jackson takes his scenario one step further.
Suppose he says that having investigated Fred's physiology, the scientists realize how by a slight modification everybody's physiology can be tweaked so as to become exactly like Fred's: capable of discriminating between the two sets of wavelengths we said Fred's was able to.
Though Jackson doesn't say so, perhaps one can think in terms of a chemical that is present uniquely in Fred's physiology and which when supplied to an ordinary person through a tablet alters the physiology in Fred's direction.
The tablet is ready. All I have to do is to swallow it.
Wouldn't this be really interesting, really exciting, asks Jackson. At last I would be on the verge of discovering what Fred's unique experience was like.
And yet we know already all there is to know physically about Fred.
Therefore the physical facts do not tell the whole story.
MARY IS A SCIENTIST WHO WORKS IN A BLACK AND WHITE ROOM
Mary is a scientist studying the neurophysiology of vision. Jackson says she is brilliant, but I think that's just because all scientists who are spoken about are spoken about as being 'brilliant'.
She is studying neurophysiology of vision - but under one striking limitation. She is obliged for some reason to conduct all her enquiries, all her investigations, within a black and white room, which has just the one way of linking with the outside world: a black and white monitor.
We suppose her to have all the information there is to have concerning what goes on in the brain and along all our neural pathways whenever we either see tomatoes etc., or use colour words.
For example, she discovers just which wavelengths of light from the sky stimulate the retina, and exactly how this retinal activity gets processed and linked to other neural activity, some of which results in activity in the vocal chords and activity in the lungs which produces what is heard as the utterance 'the sky is blue'.
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| Frank Jackson. Pc thanks to Australian National University. |
All this information, says Jackson, is certainly establishable by Mary, who is indeed a brilliant scientist, sitting in her black and white room, working with her black and white monitor.
The question then is: what will Mary learn when she is let out, or given a colour monitor? Will she learn anything new?
He says:
'It seems just obvious that she will learn something'... - something about the world, and about our visual experience of it.
But if she learns something, it must be that her previous knowledge was incomplete. But her previous knowledge embraced the whole of the physical facts. Therefore there is something more to know than the physical facts.
These scenarios in different ways put what is called the knowledge argument against 'physicalism', against the identity hypothesis in particular.
Jackson says the same kind of argument could be devised in the case of taste, hearing, and bodily sensation; and for the various other mental states which are invoked against physicalism.
END
Toamtoes pic thanks to Lucky's Real Tomatoes
Revised 31:03:03
