Volume 52, Number 11 · June 23, 2005
Letter
WHAT IS CONSCIOUSNESS?
By Stevan Harnad, Reply by John R. Searle
In response to Consciousness: What We Still Don't Know
(January 13, 2005)
To the Editors:
John Searle ["Consciousness: What We Still Don't Know," NYR, January 13] points out, rightly, that so far brain and cognitive science is merely studying the correlates of consciousness (where and when in the brain does something happen when we feel something?), but thereafter the goal is to go on to explain how those correlates cause consciousness (and presumably also why). Koch (and Crick) seem to think it's a matter of finding out when and where the bits are put together ("the taste of coffee in our mouth, the slight headache, and the sight of the landscape out the window"), whereas Searle thinks it's a matter of finding the "unified field"—but either way, it's correlates now, and the explanation of how only later.
I want to cast some doubt on that later causal explanation ever coming. The best example is the simplest one: Searle mentions just a simple feeling (anxiety)— something that is not "about" something else, just a feeling we have. So suppose we find its correlates, the pattern of brain activity that occurs whenever we feel anxious. And suppose we go on to confirm that that brain activity pattern is not only correlated with anxiety, but it causes it (in that (1) it comes before the feeling, (2) if it is present we feel anxiety, (3) if it is absent we do not, that (4) there is no other correlate or cause that we have missed, and (5) we can explain what causes that pattern of brain activity).
Now what about the "how"? How does a pattern of brain activity generate feeling? This is not a question about how that pattern of brain activity is generated, for that can be explained in the usual way, just as we explain how a pattern of activity in a car or a kidney is generated. It is a question about how feeling itself is generated. Otherwise the feeling just remains something that is mysteriously (but reliably) correlated with certain brain patterns.
We don't know how brain activity could generate feeling. Even less do we know why. This is not spiritualist voodoo. It is just an emperor's new clothes observation about the powerlessness of the usual kind of causal how/why explanation when it comes to feeling. For if you venture something like "Well, the anxiety is a signal to the organism to be careful," the natural reply is "Fine, but why did the signal have to be felt, rather than merely transmitted...?" That is the how/why problem of consciousness, and it is something that we not only still don't know but (until further notice) it looks like something we never will know.
Stevan Harnad
Chaire de recherche du Canada
Centre de neuroscience de la cognition
Université du Québec à Montréal
John R. Searle replies:
Stevan Harnad's letter raises a challenge to the very possibility of
any scientific account of consciousness of the sort that both Koch and
I favor. He says, "We do not know how brain activity could
generate feeling. Even less do we know why." And he laments the
"powerlessness of the usual kind of causal how/why explanation when it
comes to feeling."
SH:
So far this recap is correct.
It is important to understand that he is not lamenting our present
neurobiological ignorance. He thinks even if we had a perfect science
of the brain, we would be unable to answer the how/why question. I am
not convinced. Suppose we knew in exact detail all of the
neurobiological mechanisms and their mode of operation, so that we knew
exactly which neuronal events were causally necessary, or sufficient,
or both, for which subjective feelings. Suppose all of this knowledge
was stated as a set of precise laws. Suppose such knowledge were in
daily medical use to help overcome human pain, misery, and mental
illness. We are a long way from this ideal and we may never reach it,
but even this would not satisfy Harnad.
SH: So far this recap is still correct.
It is hard to see what more he
wants. If a complete science of the sort I am imagining would not
satisfy him, he should tell us what would. If nothing could satisfy
him, then it looks like the complaint may be unreasonable. It is not
clear to me what he is asking for when he asks for more.
SH: The reason
this does not satisfy me (and should not satisfy Searle either) is that
the "precise laws" we need to explain (causally) the neurobological
mechanisms and to cure the illnesses, both bodily and mental, do not
explain how or why we feel at all. Those precise same laws would just
as fully explain how/why we can and do act (move, behave, function) the
way we do (including behaving the way we do when we feel something,
such as pulling our hands away from something hot); it would explain
all the neural and environmental causes of our actions and functions,
exactly as we explain the cardiac (and environmental) causes of the
heart's actions and functions. But unlike the case of the heart, the
actions and functions of our bodies (and brains) feel like something. If our bodeis
and brains just acted and functioned -- according to the demands of
Darwinian survival and reproduction, for example -- and there was
nothing it all felt like, there would be no problem. But it does feel
like something, and I defy Searle now (or on that happy day when all
these neurocognitive mechanisms are known) to say how and why the
actions and functions are felt
-- rather than merely "functed." For the "functing" is all that
survival and reproduction call for; it's also all that causal
explanation for every other case in the universe ever provides, or can
provide. So the reason I ask for more, and what it is that I am asking
for when I ask for more, is the how and why of what makes felt function
different from all other forms of function, whether physical function
or biological function: an explanation of the fact that it is felt,
rather than merely functed.
Is it unreasonable
to ask this, and to complain when one doesn't get it? No more
unreasonable than asking for the explanation of any other otherwise
unexplained (and in this case not only unexplained, but apparently
utterly superfluous) phenomenon.
Would nothing
satisfy me? Actually, there is a very simple, natural explanation of
feeling that would fully satisfy me, and indeed it is the explanation
that most people believe to be the correct explanation, but
unfortunately it is false. There would be no feeling/function problem
if feeling were simply another, independent causal force in the
universe. If feeling were up there, along with electro-magnetism,
gravitation, and the weak and strong nuclear forces as the 5th force --
say, "telekinesis" -- then it would make no more (or less) sense to ask
how and why we feel than to ask how and why gravity pulls. But feeling
is not a 5th force. It has no
independent causal power of its own. All evidence is that it
piggy-backs (no one knows how or why) on the other 4 forces: I may feel as if I'm doing something
because I feel like it, as if my feeling were the cause of my doing;
but in reality, it is my neural mechanisms and my environment
that are doing all the causing and causing all the doing, and my
accompanying feelings are merely an inxplicable (but reliable and
predicatable) correlate. There is no "mind over matter" -- or at least
so all evidence on the conservation of energy has so far ever shown.
So, yes, feeling as a 5th force would
have been a satisfactory causal explanation -- if only it had been
true. But it is not. So we are left with an unexplained -- indeed an
inexplicable -- correlation (in the wake of the failure of the direct
causal explanation that would have accounted for feeling so naturally
and satisfyingly).
Ultimately I think that Harnad has a deep philosophical worry, and
it is one that we should all share. It seems astounding that objective
neuronal processes should cause our subjective
feelings.
SH: Whenever we are at a loss, we tend
to multiply terminology (and thereby also the apparent number of
entities to explain, or, equally, of the number of candidates for
explaining them). Explaining how/why functions could be felt was
enough. We don't have to add that "objective functions" are being
"subjectively" felt: How else does anything else get felt but
subjectively? And what else can functions be in a feelingless universe
than "objective"? The mystery is already there in the very existence of
feelings. That's why we, in our frustration and desperation, invented
the notion of the immaterial and immortal soul!
But in coping with this sense of mystery we should remind
ourselves that it is just a plain fact that neuronal processes do cause
feelings, and we need to try to understand how. We should share his
sense of mystery, but not let it discourage us from doing the real work.
SH: We can and
should and will learn how to predict feelings from function: The
correlation is reliable. So once we isolate and explain the relevant
functions, they will reliably predict the correlated feelings. I'll
preconcede even more: Those functions will cause those feelings -- somehow,
though we won't be able to explain how; we'll just be able to predict
it, as in weather-forecasting (except that the functional doings of
wind and air and water are fully explained by an constituted in their
causal antecedents). And the buck will stop there, because the feelings
themselves (as opposed to their neural causes/correlates) will not have
any independent causal power of their own, no matter how much they may feel as if they do.
He is convinced that the mystery of consciousness is unique. But it
is well to remind ourselves that this is not the first time we have
confronted such mysteries. From the point of view of Newtonian
mechanics, electromagnetism seems metaphysically mysterious. How could magnetism
ever be explained by Newton's laws?
And from the point of view of nineteenth-century science, life
seemed a mystery. How could mechanical processes explain life?
As we attained a much richer scientific understanding, these mysteries
were overcome. It is hard to recover today the passions with which
mechanism and vitalism were once debated. I am urging that the right
attitude to the problem of consciousness is to overcome the mystery by
increasing our knowledge, in the same way that we overcame earlier
mysteries.
SH: It seems clear
that physico-mechanical, chemical and biological structures, actions
and functions never raised a problem of principle for causal/functional
explanation, just a practical challenge. Imagining that the lack of an
explanation was owing to a fundamental mystery rather than to ignorance
was just a case of failure of imagination and faulty reasoning. A
clever enough person could have proposed a perfectly viable explanation
by way of a speculative hypothesis to show that nothing supernatural
was necessary in principle to account for all known function, whether
inroganic or organic.
But
I think there was a bit more that drove people to vitalism than merely
the daunting challenge of explaining biological action and function: I
think vitalists had feelings
in mind -- life as sentient matter -- all along. That was the animism
that was implicit in vitalism. Which makes vitalism into just another
variant of belief in an immaterial and immortal soul. But since the
only viable version of that hypothesis would be feeling as a fifth
force, and since that hypothesis is false, the only remaining rational
option (on all the evidence) is to admit, fairly and frankly, that not
only do we have no idea how and why certain functions are felt, but
that we never will. And that far from being a shortfall that can be
pooh-poohed as destined to dissipate much the way other bit of our
ignorance have dissipated, this one might be a shortfall endemic to
causal/functional explanation itself -- or rather, of the explanatory
power of causal/functional explanation, given that explanation itself
has a felt dimension (and one that is utterly lacking in any of the
gestures toward explaining feeling to date).
Our most fundamental disagreement is harder to state. I believe his
sense of "how/why" demands more than science and philosophy can offer.
In the end when we investigate nature we find: This is what happens.
This is how it works. If you want to know how/why a body falls, the
standard answer is to appeal to gravity. But if you want to know
how/why gravity works, I am told that the question is still not
answered. But suppose it were, suppose we had a unified theory of
everything that explained gravity, electromagnetism, and everything
else. That would still leave us with the question, Why are the data
accounted for by this theory and not some other? In the end, how/why
questions stop with theories that state how nature works and the
mechanisms according to which it works.
SH:
One would have thought so -- and one would have entirely agreed with
Searle -- had the universe consisted only of insentient function (like
gravitation or electromagnetism) or had feeling turned out to be one of
the basic forces of nature. But neither of these is true: There is no
telekinesis, yet some functions are felt; so and we have to own up to the
fact that not only do we not have the faintest idea how or why, but
there is every reason to believe we never will.