Sunday, September 21, 2008

The Explanatory Gap

Nothing is more obvious or immediate to our minds than the fact of our own consciousness. And yet, consciousness seems so bizarre and mysterious, some say it is beyond any hope of an explanation. How can something be so clear and present in our minds, and at the same time be so hard to understand?

Philosophers and scientists have argued for ages about how to solve this puzzle, and sometimes about whether or not there really is a puzzle at all.

My view is that consciousness is not a philosophical puzzle, but a scientific issue which can only be worked out through a better understanding of physiology. In our case, that means understanding how our bodies and brains function.

One of the reasons consciousness is so valuable to us is that it allows us to capitalize on amazingly complex information processes without having to pay attention to many of them. If we had to focus on everything going on in our heads, we'd never get anything done.

Consciousness is not directly concerned with the underlying processes that make it possible, because that is not what consciousness is. Consciousness is that level or facet of information processing which integrates our conception of ourselves. It takes our sensations and perceptions, including the inner perception of language-formation that we think of as an ongoing monologue in our heads, and organizes around them a single, coherent narrative of who we are. We might say that consciousness is the very process of generating a sense of a self--be it a self-in-the-world, a self-reflecting-on-the-nature-of-evil, a self-eating-corn, or whatever.

Consciousness does not require us to be conscious of how we are conscious. If it did, it would be enormously inefficient. This is why we can be conscious, and be so intimately in touch with our consciousness, without having any idea of what consciousness is or how it works.

When looked at from the perspective of our own awareness, our own consciousness is the tip of the iceberg of our cognition, and the majority of the processes which support it remain underneath the surface. Conversely, when looked at in the laboratory, from the outside, all we can see is the mind-boggling complexity of the brain. We have yet to fully grasp how the idea of the self is integrated in the brain. Our deficit of scientific knowledge may one day be overcome with the right theoretical and experimental tools. Then again, it might not. We just have to keep trying and see how far we get.

I call this The Default View of consciousness, because it does not claim anything fundamentally unusual about consciousness. It does not assume that there is anything so extraordinary about consciousness that it can never be known through the process of scientific discovery.

Many scientists and philosophers are quick to say, “hey, hold on a minute. Obviously there is something extraordinary about consciousness. If there weren’t, it wouldn’t seem like such a puzzle.”

Of course consciousness is extraordinary. But we cannot claim it is so extraordinary that it will forever elude a scientific explanation. We must treat consciousness like anything else in nature—something perhaps more complex and unusual than anything else we’ve found in the universe, but still a part of the universe which we can approach like any other.

This isn’t good enough for some scientists and philosophers. They claim that there is an explanatory gap. The idea is that consciousness involves subjective experience, and subjectivity is not something you can understand objectively.

You may have a complete, objective model of the human brain and human behavior. You may understand everything science can teach us about human experience. And yet, you will always leave something out. You will leave out the “what it is like” for a conscious subject to experience their own consciousness. Right?

I know it seems that way to many, but I do not think it is so. The Default View is the only tenable position here, and the reason is simple. If there were any evidence that consciousness (or anything else) were so unique that it could not be explained objectively, that evidence could not be shared. For, if it could be shared, then it would be objectively determinable. Therefore, from a scientific point of view—that is, from a point of view which regards facts as sharable and repeatable through well-documented experiments—there can never be any evidence that consciousness (or anything else) is beyond the hopes of a scientific explanation. (I elaborate upon this argument in a more recent blog post.)

It is impossible to argue against the Default View, unless you want to argue against the very logic of scientific discovery. As it turns out, some philosophers want to do this. Fortunately for the rest of us, they cannot undermine the logic of science. All they can do is confuse the debate.

David Chalmers
is a famous case. He is well-known in the philosophy of mind, primarily for his arguments for the existence of an explanatory gap. He says there is a “hard problem” of consciousness, which is the problem of understanding how physical processes (such as those occuring in our brains) can give rise to subjective experiences.

Chalmers argues that no scientific understanding of the physical mechanisms of human behavior will ever produce an understanding of the subjective experience of consciousness. He says that, even if we were to have beings that walked and talked just like human beings, with brains that worked just like human brains work, it is conceivable that they might not be conscious. (Such hypothetical beings are called “philosophical zombies,” though as far as I know they are not stipulated to eat human brains or engage in otherwise distasteful behavior.)

Let me repeat this, just so it’s clear. Chalmers says that he can conceive of a being that is scientifically indistinguishable from a human being in every way. Such a being, he says, could conceivably lack consciousness. Thus, he concludes, consciousness is not a matter of human physiology and behavior. For, if it were, then we could not conceive of the one without also conceiving of the other. It would be like thinking of a ball without thinking about roundness. You can’t do it.

This is called the conceivability argument. The problem is, David Chalmers cannot do what he says he can. He cannot conceive of a being that is scientifically indistinguishable from a human being in every way. At least, not yet. Nobody can. This is obvious from the fact that no scientist has yet to fully understand the workings of the human brain. We can safely say, therefore, that when David Chalmers talks about philosophical zombies, he does not know what he is talking about.

The conceivability argument should not weigh down discussions of consciousness. And yet, it often does. It fascinates people, not because it is logically sound, but because it resonates with their intuitions about consciousness. There just has to be an explanatory gap, they say. Subjective experience simply cannot be explained in objective terms.

This intuition is so strong, many confused intellectuals have tried to seek refuge in quantum mechanics. They say that consciousness must arise out of the wholly bizarre and incomprehensible mechanisms of quantum physics, because classical mechanics is too simple, too predictable, to produce something as complex and mysterious as consciousness.

Of course, there is no evidence that classical mechanics is incapable of explaining consciousness. On the contrary, consciousness appears to occur at a very high level of neural activity, and not at a level that would seem to involve quantum effects.

The argument for "quantum consciousness" is just wishful thinking, and not based on reason or evidence. The wish, apparently, is that consciousness will never be explained, and that its mystery is inextricably linked with the greatest mysteries of the universe. This wishful thinking, like all wishful thinking, is based on a fear. In this case, the fear is that an explanation of consciousness would somehow diminish the importance or wonder of humanity, taking away our value and even our freedom. As though actually understanding how we work would somehow hurt us.

The lack of reason here is astounding. Yet, we still have scientists—neuroscientists, even—who claim there is an explanatory gap. Antonio Damasio refers to it in passing in one of his popular books, and V. S. Ramachandran has written and spoken about it at length.

According to Ramachandran, the explanatory gap can be overcome by directly linking one brain with another. In that way, he says, one consciousness can understand the contents of another. So, he says, there is nothing truly bizarre going on with consciousness. It’s all in the brain.

While Ramachandran’s scenario would be interesting for a number of reasons (for example, it could demonstrate that consciousness need not be a solitary experience), it ultimately misses the point.

The point is, scientific explanations need not exhibit the properties of the phenomena they describe. A scientific explanation of a bouncing ball need not be bouncy. A scientific description of a nuclear reaction need not produce nuclear radiation. Properties can be described in their absence. This does not mean that the descriptions are incomplete, or that there is something essential about the phenomena that eludes scientific understanding.

So, a blind person can, in theory, understand everything there is to know about color vision. Just like they can understand the properties of bouncing balls without having any. They don’t need to have their own, direct experiences of color vision, because they can have the means of detecting color vision indirectly. They can have prosthetic color vision. (For more on this, see my previous blog entries on Frank Jackson's knowledge argument: here, here, and here.)

Let’s say we have a scientifically complete understanding of human brains and behavior. We seem to know exactly what it means for a person to have conscious experiences. Now, critics like Chalmers would say that we haven’t actually explained “what it is like” to have a conscious experience. Even if our understanding is so great that we could actually reproduce a fully-functioning human being, with a brain that functions exactly like a human brain—Chalmers would say that we would not have reproduced consciousness.

If DNA can do it, why can't we?

The man-made human beings would talk at length about their inner subjective experiences, just like everybody else. They would talk about love and fear, and they would appear to act on these feelings just like you and me. But, Chalmers says, they wouldn’t be conscious.

How would we know? How do we know that anybody has consciousness?

How does Chalmers know that his parents and friends have consciousness?

If a being presents us with all the signs of consciousness, then it only makes sense to say it has consciousness.

Chalmers says no physical signs are good enough, which serves only to define consciousness out of existence. According to Chalmers, consciousness is a non-entity, with no discernable functions, qualities, or characteristics. We may as well say that apples have consciousness--but not genetically modified apples, of course.

From Chalmers' perspective, there is no reason to think that you are any more conscious than a cloud of smoke, and the value of attributing consciousness to either you or the cloud is non-existent.

The arguments for an explanatory gap are thus not only unscientific—they are logically unsound and philosophically absurd.

Of course, it is conceivable that we will never completely understand consciousness. However, there is no way of deciding that question before the fact.