Volume 52, Number 11 · June 23, 2005
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 is 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."
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. 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.
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. 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.
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.
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.