- seCtIon one: tHe PRoBLem
But if you think that consciousness has effects or functions, you will disagree with
Chalmers. For example, if you believe we need to be conscious to think, speak, or
make difficult decisions, then a creature without consciousness would be unable
to do these things. This means it could not be indistinguishable from a conscious
person, so zombies could not exist. Another way of saying this is that if zombies
are possible, then consciousness must be superfluous, a kind of epiphenomenon
that exists but does nothing. This is the idea of ‘consciousness inessentialism’.
Imagine zombie earth: a planet just like ours, peopled by creatures who behave
exactly like us, but who are all zombies. There is nothing it is like to live on zombie
earth. In ‘Conversations with Zombies’, philosopher Todd Moody (1994) uses the
following thought experiment designed to reject consciousness inessentialism.
He imagines the whole zombie earth to be populated by people who use such
terms as think, imagine, dream, believe, or understand, but who cannot understand
any of these terms in the way we do because they have no conscious experience.
For example, they might be able to talk about sleep and dreaming because they
have learned to use the words appropriately, but they would not have experi-
ences of dreaming as we do. At most they might wake up to a sort of coming-to-
seem-to-remember which they learn to call dreaming.
On such an earth, Moody argues, the zombies might get by using our language, but
zombie philosophers would be mightily puzzled by some of the things we conscious
creatures worry about. For them the problem of other minds, or our worries about
qualia and consciousness, would make no sense. They would never initiate such con-
cepts as consciousness or dreams, so zombie philosophy would end up quite different
from ours. From this he argues that although the zombies might be individually indistin-
guishable from conscious creatures, they would still show the mark of zombiehood at
the level of culture. At this level, consciousness is not inessential – it makes a difference.
Moody’s thought experiment inspired a flurry of objections and counter-argu-
ments from philosophers, psychologists, and computer scientists (Sutherland,
1995). One of the main objections is that Moody has broken the rules of the
thought experiment. It is worth reminding ourselves what
exactly those rules are.Chalmers’s core definition concerns the physical: ‘someone or
something physically identical to me (or to any other conscious
being), but lacking conscious experiences altogether’ (1996, p.
94). But this entails behavioural identity too: ‘my zombie twin
is by definition physically identical to me over its history, so it
certainly produces indistinguishable behavior’ (1996, p. 120).
This means that the people on zombie earth must be truly and
wholly indistinguishable in all their actions, too. If their philoso-
phy, or the terms they invented, were different, then they would
be distinguishable from us and hence not count as zombies. If
you really follow the rules, there is nothing left of the difference
between a conscious human and a zombie.
Then again, maybe Moody’s argument does exactly what a
thought experiment is meant to do: helps us see something that
wasn’t already totally obvious. If you imagine a physically identi-
cal zombie and ask yourself what zombie culture would be like,‘I have a clear picture of
what I am conceiving
when I conceive of a
zombie’
(Chalmers, 1996, p. 99)
FIGURE 2.4 • Which is which? Can you tell?
Can they?