Minds and Computers : An Introduction to the Philosophy of Artificial Intelligence

fficient for
something being a mental state.
Both objections seek to highlight the importance of qualia in
mental life and aim to establish an explanatory burden on theorists of
mind to account for qualia. Let’s first consider the inverted spectrum
objection.
Whenever I’m in the presence of objects with certain surface
reflectance properties, under certain lighting conditions, I have a per-
ceptual experience such that if someone asks me what colour I per-
ceive the object in question to be, I will respond ‘blue’. The experience
I have when observing the Pacific Ocean in bright sunlight is a para-
digm example of what I refer to by the colour term ‘blue’.
Whenever Sue is in the presence of the same objects under the same
lighting conditions and I ask her what colour she perceives, she also
replies ‘blue’. Whenever I see an object which I perceive to be yellow
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and say ‘that looks yellow’, Sue is in agreement. So it is with all our
other colour terms. In other words, we concur always and everywhere
on the extension of our colour terms.
The problem is that I don’t have direct access to Sue’s perceptual
experiences, only to her reports of her experiences. Given that we
always and everywhere point to the same things when uttering
colour terms, I presume that when Sue has a perceptual experience
which she reports as ‘blue’ that she thereby has a perceptual experi-
ence just like the one I have when I experience blueness. For all
I know, however, it may well be the case that whenever Sue perceives
what she reports as ‘blue’, she is actually having a perceptual experi-
ence such that if I were to have that experience I would report it as
being ‘yellow’. In fact, for all I know, this may be the case for all our
colour terms – our colour spectra may be completely inverted with
respect to each other.
The argument against the adequacy of a functional account of
mental terms which we draw from this thought experiment runs along
the following lines. My mental state of ‘perceiving blue’ and Sue’s
mental state of ‘perceiving blue’ are functionally equivalent. Our
respective states mediate characteristic blue-type stimulus, blue-
perceiving behaviour and other mental states in just the same way.
According to the functionalist then, our respective states are equiva-
lent and there is nothing to distinguish the two. After all, the only pos-
sible distinction between mental states, on a functionalist account, is
a distinction in function. It seems quite clear, however, that there is
something quite di
fferent about our respective states of ‘perceiving
blue’. Sue, by virtue of her inverted colour spectrum, is perceiving
what I would call ‘yellow’.
It is not at all clear what to say about this argument and I certainly
don’t intend to rule on it here. The literature, as I have said, is very
much divided on the importance of qualia.
On the one hand, it seems clear that there is an important distinc-
tion between the two mental states in question which cannot be
accounted for in terms of function alone. What it is like for me to per-
ceive blue is not at all what it is like for Sue to perceive blue. Quite dis-
tinct qualia attach to the two experiences.
On the other hand, it is not obvious just what hangs on this. After
all, if we are always and everywhere in agreement with respect to the
extensions of our colour terms, surely this is all that is important.
Does it really matter that I would call her ‘blue’ experience a ‘yellow’
experience? Especially since this is something that neither of us, nor
anyone else, could ever know?
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The second objection against the adequacy of a functional account
of mentality is known as the absent qualia objection, or – more
entertainingly – the zombie objection.
Consider, if you will, a being indistinguishable for all intents and
purposes from you and me. Let’s call this being Imitation Man.
Imitation Man has a regular life, just like you and me. He has likes
and dislikes, goals and ambitions, beliefs and desires – in short he is
just like any other human being. When asked about his experiences,
Imitation Man will give the kind of answers we would expect any
other person to give – he will tell us that his pain hurts, that the experi-
ence of listening to certain music is pleasurable and that chocolate ice
cream tastes marvellous.
Unlike you and me, however, Imitation Man is completely lacking
in qualia. He is what we might call a ‘zombie’. His pain doesn’t
actually feel like anything. There is nothing that it is like for him to
listen to music or to taste ice cream. There is no way for us to ever dis-
cover this though since we do not, of course, have direct access to his
experiences.
This in no way speaks against his functional equivalence with other
human beings. His pain state still plays the functional role that pain
states play in everyone else, as do all his other mental states. They
simply don’t feel like anything.
The argument to be made against functionalism here should be
obvious. Imitation Man’s pain state, for instance, is functionally
equivalent to ours – it mediates relations between stimulus, behaviour
and other mental states in just the way our pain state does. If
Imitation Man’s hand is placed on a stove, he will yell, cry ‘ouch’ (or
some other appropriate expletive), seek to remove his hand from the
source of heat, engage in hand-soothing behaviour, weep and moan,
and so on. Imitation Man’s pain and our pain are, therefore, equiva-
lent simpliciter on the functionalist account . Yet it seems clear that
Imitation Man’s pain is a rather di
fferent thing to our pain – his pain
doesn’t hurt.
As with the inverted spectrum objection, it is not at all clear what
one should say to the absent qualia objection. Once again, I shan’t
rule on it here but will simply indicate the two kinds of ways one
might be tempted to respond.
On the one hand, it seems that the example is unfairly prejudiced
against the adequacy of functional explanation. It assumes that carry-
ing out all the various functions characteristic of human mental life is
not ipso facto having qualia. In fact, it is tempting to charge the absent
qualia objector with begging the question against the functionalist.
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However, there is nothing in the functionalist account so far which
maintains the presence of qualia as a straightforward consequence of
carrying out the various functions characteristic of mentality.
The functionalist only maintains that a functional account of
mental states is an adequate account, so the absent qualia objector
doesn’t quite beg the question. It is di
fficult to appreciate, however,
how Imitation Man’s pain state could be functionally equivalent to
ours without his pain being hurtful. After all it is the very hurtfulness
of our pain which motivates our pain alleviating behaviour, is it not?
There is still a sense in which the absent qualia objection is somehow
loaded against the functionalist.
On the other hand, the absent qualia objection seems to bring out