Wednesday, 22 May 2013
An e-mail has just invited me to consider whether phenomenal consciousness is a causally inert epiphenomenon, and a pointless by-product of brain activity. It is the sort of question that can be transformed into a different question.
First, to what does the claim amount?
It is not a claim about self-awareness of the type that underpins an agent's knowledge that the actions that she can make happen just by thinking, are the actions that will take place in her immediate vicinity, and are performed by the entity that must be kept fed in order for her thought processes to continue. That sort of self-consciousness can be characterized as having a grasp of what Perry called the essential indexical. It is the sort of self-consciousness that lies at the heart of Lucy O'Brien's argument in her book, Self-Knowing Agents. It is something that must be represented in our brain cells, one way or another, in order for us to function as we do.
Rather, the claim is about how things feel to us, the qualia (or apparent qualia, if one thinks that there are no qualia) that we have, but that zombies would not have. So the second part of the claim, that phenomenal consciousness is a pointless by-product of brain activity, is a claim that zombies could do just as well as we do. It might happen to be that any creature that functioned as we function could not be a zombie, for example, because we would need to wire up the cells in certain ways which would inevitably produce phenomenal consciousness as a by-product. But even if that were so, the second part of the claim could still be made. It would merely need to be worded as "Disregarding the practicalities of making zombies, they could do just as well as we do".
If, however, one were able to substantiate the second part of the claim, in the form of a claim that zombies could do just as well as we do, that would not mean that we would have established the first part of the claim. (It may be that the second part of the claim could be taken in some other form, such that substantiating it would substantiate the first part of the claim, but it is not obvious how to re-cast the second part in order to give this result.)
We would not be able to move straight from the second part to the first part, because phenomenal consciousness might be causally effective in human beings, creatures who have it, even though an alternative way of achieving the same results that we achieve, an alternative that did not involve phenomenal consciousness, would be available. We should not suppose that the difference between a human being and a zombie is simply the presence or absence of phenomenal consciousness, with no other differences. And if there are other differences, such that we would not get from a zombie to a human being simply by adding phenomenal consciousness, those differences could build in a causal role for phenomenal consciousness.
We need to say something about how phenomenal consciousness could have a causal role. It could be said that only fundamental particles and forces have causal roles. But that would be a very narrow way of speaking. We are more inclined to say that macroscopic objects also have causal roles. Now suppose that a subject has his fingers on some buttons, which carry modest electrical charges that produce a pleasant tingling sensation, but which are also getting steadily hotter. If a particular configuration of brain cells corresponded to a particular feeling in the subject, and could not be picked out in any other way than by saying "this is the configuration when the subject feels heat at his fingertips", and an analysis of his brain processes showed that the configuration led to conscious thoughts about when it would become sensible for him to withdraw his fingers and forgo the pleasant tingling sensation, then it would not be obviously inappropriate to say that the feeling played a causal role, any more than it is inappropriate to say that a ball that rolls off a table and onto the floor plays a causal role in making a noise, rather than saying that the particles of which the ball is comprised play causal roles in disturbing particles in the atmosphere. Berent Enç's thoughts on causation and conditionals, in his book How We Act, are relevant here.
It would not be obviously inappropriate to speak in that way, but it might still be inappropriate. What might make it appropriate, or inappropriate?
A claim of appropriateness would best be sustained by a claim that states of phenomenal consciousness were on a par with macroscopic physical objects. There is a sense in which both are not really there, but are mere causally inert epiphenomena of the fundamental particles and forces. If they were causally inert in the same sense, that would strengthen the position of those who said that it was appropriate to regard states of phenomenal consciousness as more than epiphenomena, to the extent that it was appropriate to regard macroscopic physical objects as more than epiphenomena.
So the new question, into which we can transform the original question, is this: Are states of phenomenal consciousness epiphenomenal on the fundamental particles and forces, in the same way as macroscopic physical objects?
One reason to say that states of phenomenal consciousness and macroscopic physical objects were epiphenomenal in different ways, would be that laws of the same general type, physical laws, give us a grip on the behaviour of particles, and on the behaviour of macroscopic physical objects. It is a debatable claim, but not a crazy claim, that we could derive the whole of chemistry and biology from physics, too. (This is an upwards claim, different from the claim that we could reduce biology and chemistry downwards to physics.) We could claim that any emergence would not obstruct such an upwards derivation.
But then, could one also argue that no emergence would get in the way of an upwards derivation of facts about states of phenomenal consciousness? If it would not, and if this upwards derivation were feasible, we would have failed to separate off consciousness as something different from biology in a relevant way.
One sign that there might be an obstacle to such an upwards derivation is that descriptions of states of phenomenal consciousness are readily appreciated by us, but they might not mean anything to, for example, Martians, whereas human biology would be perfectly meaningful to Martians.
Another sign is that we do not yet have much idea of what such an upwards derivation would look like, whereas we have a pretty good conception of upwards derivations of chemistry, and of biology, from physics. But it would be unwise to assume that this is how things will rest. Our knowledge of the brain has advanced enormously over the last 20 years. We do not know how much we will learn in the next 20 years.
Finally, we must consider the objection that if we did see how facts about states of phenomenal consciousness were to be derived, the descriptions of the derived objects would not look like descriptions of states of phenomenal consciousness. They would be descriptions of brain states. The descriptions would not glow with the feelings that we have, when our brains are in those states. But it is only Martians who definitely could not see the descriptions as glowing with those feelings. If we were to follow a Churchland-type programme of reform of our manner of speaking, so that we started to speak in terms of brain states, and if we associated descriptions of brain states with inner feelings, the descriptions might well come to glow with the corresponding feelings, even when we read them in neurology textbooks.