Think: A Compelling Introduction to Philosophy (8 page)

Descartes left us with a problem of knowledge. He also left us
with severe problems in understanding the place of our minds in
nature. And finally the entire scientific revolution of which he was
such a distinguished parent left us with profound problems of understanding the world in which we are placed. We have seen something of the problem of knowledge. The next chapter turns to
problems of mind.

SUPPOSE WE PUT ON ONE SIDE the general problem of harmony
between the way we take the world to be and the way the world is.
We shall keep our fingers crossed, supposing that we do really
know what we naturally take ourselves to know. But how well do
our views hang together? Descartes left us with our own selves and
our own minds as special, intimate, objects of immediate knowledge. Or rather, each of us is left with his or her own mind as a special, intimate, object of immediate knowledge. For even if I can
climb out of the seas of doubt onto the Cogito, I cannot climb out
onto the nature of your mind. So how then do I know anything
about your mental life? How do I know, for instance, that you see
the colour blue the way that I do? Might it be that some of us feel
pain more, but make less fuss about it, or that others feel pain less,
but make more fuss? How do we begin to think about mind and
body, brains and behaviour?

THE GHOST IN THE MACHINE

We have seen how Descartes's strategy led him to regard knowledge of our own minds as more secure and certain than knowledge
of the rest of the world. But Descartes was also a scientist. He made
foundational discoveries in optics. He practised dissections, and
knew a fair amount about the transmission of impulses through
the nerves to the brain. He knew this took place by means of a physical transmission, a 'pull' or `violent motion' of the nerves, or as
we would now think, an electrochemical impulse transmitted
through the nervous system. The ordinary senses of sight, touch,
taste, smell, and hearing activate the nervous system, which transmits messages to the brain. The brain is not, of course, an undifferentiated lump. Bits of the brain transmit signals to other parts of
the brain and back to the body: whole patterns of activation get set
up. All this is part of neurophysiology. These events can in principle be seen in public: with the right instruments, the patterns of
activation can he shown to a classroom.

And then what?

Well, then there is the magic moment. The'mind' (the thinking
thing, or'res cogitans') gets affected as well, and the whole world of
experience opens up. The subject sees colours, hears sounds, feels
textures and temperatures, and has sensations of taste and smell.
This world of experience is composed of mental events or events
within subjective consciousness. These events in the subject's consciousness cannot he seen in public. They are private. The whole
classroom may see some neurones firing, but only the one person feels the pain. Descartes actually located the place where the magical event takes place. For quite sensible neurophysiological reasons
he thought that the pineal gland, a structure lying centrally within
the brain, must be the place where messages were conducted from
the realm of physics to the realm of the mental.

For Descartes it is not only that mental events are distinct from
physical events. They also belong to a distinct kind of substanceimmaterial substance-a kind of ghost-stuff or ectoplasm. Strictly
speaking if I say, `I thought of the Queen and I saluted,' there is a
kind of ambiguity: the`l'that is the subject of the thought is not the
`I, the body, that salutes. Thoughts and experiences are modifications in one kind of stuff; movement and position belongs to the
other. This part of Descartes's doctrine marks him as a 'substance
dualist: It is not just that there are two kinds of properties (mental
properties and physical properties) and that persons can have
both. It is that there are two kinds of bearers of properties as well.
Of course this is theologically convenient: it opens the way to the
immortality of the soul, since there is no reason for soul-stuff to
have the same life span as anything like a physical body. But substance dualism is not compulsory. One could hold that mental and
physical properties are very different but that the one organized
body has them both-after all, mass and velocity are two very different kinds of property, but projectiles have them both. People
who hold that there are two kinds of property (mental and physical) but that they can belong to the one kind of stuff (whatever
large animals are made of) are called property dualists.

Descartes leads us to the view neatly summed up by Gilbert Ryle
(1900-76) as holding that the human being is a'ghost in a machine' Events in the machine, the physical body, are like other events in
the physical world. They consist in the interactions of familiar
kinds of stuff: molecules and atoms, electrical fields and forces.
Events in the ghostly part, the mind, are altogether different. Perhaps they are events in some kind of ghost-stuff-ectoplasm, or
the non-physical stuff that spirits and angels are made of. Spirits
and angels do without the physical embodiment altogether, in the
popular mind. But in the normal human being there is a close correlation between events of the one kind and those of the other:
sticking a pin in someone makes physical changes, but it also
causes a mental event of feeling pain. And vice versa: the mental
event of remembering a blunder may cause physical events such as
groaning and blushing. So events in the one realm may affect those
in the other. But in principle the two realms are entirely distinct.

ZOMBIES AND MUTANTS

Of course, this view is not peculiar to Descartes. It is the view presupposed by many of the world's great religions: it is part of any
doctrine holding that we can survive bodily death, or that our soul
can go one way while our body goes another. Yet it is a view that
faces enormous, and arguably insurmountable, problems.

The first family of problems is epistemological. I just said that in
the normal human being there is a close correlation between
events of the one kind and those of the other. But how are we entitled to believe that? Here is one way things might be:

The Zombie Possibility. Zombies look like you and me,
and behave like you and me. Their physical natures are indistinguishable. If you opened a Zombie brain, you would
find that it functions exactly the same way as your brain or
mine. If you prick a Zombie, he or she will go `ouch', just like
you or me. But Zombies are not conscious. There is no
ghost within.

Because Zombies look and behave just like you and me,
there is no way of telling which of us are Zombies and
which are conscious in the way that you and I are. Or at any
rate, in the way that I am. For now I have raised the Zombie
possibility, I see that I can't really be sure about you or anyone else. Perhaps consciousness is an extremely rare correlate of a complex system of brain and body. Perhaps I am
the only example of it: perhaps the rest of you are all Zombies.

Here is another way things might be:

The Mutant Possibility. Mutants look like you and me, and
behave like you and me. Their physical natures are indistinguishable. If you opened a Mutant brain, you would find
that it functions exactly the same way as your brain or
mine. If you prick a Mutant, he or she will go `ouch, just like
you or me.

Unlike Zombies, Mutants are conscious. There is a ghost
within. But the events in the Mutant ghost are not like those
we expect. A Mutant who is pricked, for instance, may experience a mental event like hearing middle Con a clarinet.
She still goes `ouch, for, since her brain functions like ours
and she behaves like us, being pricked with a pin starts
processes that cause changes that eventually end up with
her saying 'ouch', just like the rest of us. Perhaps when she does instead hear middle C on a clarinet, she feels awful
pain, but it only makes her smile beatifically. A Mutant who
sees British post-boxes may see them as yellow; one who
sees daffodils may see them as blue. Events in the Mutant's
consciousness bear no relation to the events in your mind
or mine. Or at any rate, no relation to the events in my
mind. For now I have raised the Mutant possibility, I see
that I can't really be sure about you or anyone else. Perhaps
the rest of you are all Mutants, compared with me.

The point about these possibilities is that they seem to be wide
open, on the Cartesian dualist account of mind and body. They are
unnerving possibilities, and ones we do not normally consider (although I suspect that they cross our minds more often than the
outlandish possibilities of the first chapter).

One way to react to them is to bite the bullet. You might say: all
right, let us suppose these are wide-open possibilities. Perhaps I
can never really know what the mind of another person is like,
what mental events occur within it, or even whether there is any
mental life going on at all. But can't I still suppose that other people's mental lives are much like mine? Can't I reasonably use myself
as a model for all the rest? It would be not so much a case of knowl-
edgeas of a hypothesis or conjecture, but it perhaps it is a reasonable
conjecture to make. This is called the argument from analogy to
the existence of other minds.

The problem with this argument is that it seems incredibly
weak. As the great Austrian philosopher Ludwig Wittgenstein
(1889-1951) dismissively asked: 'And how can I generalize the one
case so irresponsibly?' The mere fact that in one case-my own perhaps as luck has it, there is a mental life of a particular, definite
kind, associated with a brain and a body, seems to be very flimsy
ground for supposing that there is just the same association in all
the other cases. If I have a box and it has a beetle in it, that gives me
only very poor grounds for supposing that everyone else with a box
has a beetle in it as well.

Perhaps worse, it gives me very poor grounds for denying that
there are beetles anywhere else than in boxes. Maybe then things
that are very different from you and me physically are conscious in
just the way that I am: rocks or flowers, for example.

You might be inclined just to `shrug off' the Zombie and Mutant
possibilities. You might reflect that they are pieces of philosophical
fantasy, unreal or at any rate unverifiable. But that is not an intelligent reaction. The possibilities are indeed unverifiable. Neurophysiologists, for instance, cannot find conscious experience in the
way they can find neurones and synapses and patterns of brain activity-as we put it, they cannot display it on the screen to their
students in the lecture theatre. But then, on Cartesian dualism, the
possibilities we all naturally believe in, namely that other people
are not Zombies, and not Mutants, are themselves unverifiable!
They amount to blind articles of faith. Someone holding the Zombie possibility is no worse off than the rest of us in that respect.

In fact, if our conception of mind allows the Zombie and Mutant possibilities, we might even suppose them quite probable, or
at least as probable as anything else. For if it is not a priori false that
other people are Zombies, why should it be a priori less probable
than that they are conscious like me?