I am just back from the four-day “Toward a Science of Consciousness” conference in Tucson. I heard 32 papers on a wide variety of topics and I’m trying to tell myself what I’ve learned about consciousness. Today, I’ll focus on the most fundamental of the difficulties in this area, known to afficionados as “the Hard Problem of consciousness”. The following four statements explain the problem in a way that leaves open to many different kinds of response to it.
1. Data concerning our sensations and feelings correlate with data concerning the firings of neurons in our brains.
There is overwhelming evidence for this statement. Strokes in the back of the head, or severe injuries there, cause loss of vision. The extent of the area in which one can no longer see is well correlated with the extent of the damage. Pin pricks normally hurt; but if injury or drugs prevent the neural signals they cause from reaching the brain, you won’t feel a thing. Direct electrical stimulation of some brain locations produces experiences. And so on.
2. What neurons do is to fire or not fire.
Neurons can fire faster or slower. There can be bursts of rapid firing, separated by intervals of relative quiescence, and there can be patterns of such bursts. With 100 billion or so neurons, that allows an enormous range of possible combinations of neural activities. We know of no other aspects of neural activity that are relevant to what we are experiencing.
3. We experience a large number of qualities – the colors, the tastes, the smells, the sounds, feelings like warmth, itchiness, nausea, and pain; and feelings such as jealousy, anger, joy, and remorse.
4. The qualities noted in 3. seem quite different from the neural firing patterns in 2, and from any complex physical property.
The Hard Problem is this: What is the relation between our experiences and their qualities, and our neural firing patterns? How can we explain why 1. is true?
There are two fundamental responses to the Hard Problem, and many ways of developing each of them. They are:
Physicalism. Everything is physical. Experiences are the same things as neural events of some particular kind. (It is not claimed that we know what particular kind of neural event is the same as any particular kind of experience.) The explanation of 1. is that the data concerning experiences and neural events are correlated, since experiences and neural events are just the same thing. It’s like the explanation of why accurate data about Samuel Clemens’ whereabouts would be perfectly correlated with accurate data about Mark Twain’s whereabouts.
Dualism. Experiences are not identical to neural events. 1. is true either because neural events cause experiences, or because some events have both neural properties and other properties that cannot be discovered by the methods of science.
Today, the dominant view (about two to one, by my unscientific estimate) is physicalism. The reason is suggested by my descriptions. Dualists evidently have to say how neural events can cause experiences, or explain the relation between the properties known to science and the properties not known to science. Physicalists have no such task: if there is just one thing under two names, there is no “relation” or “connection” to be explained.
But physicalism has another task, namely, to explain how 4. can be true. According to physicalism, blueness = some complex physical property X, the feeling of nausea = some complex physical property Y, and so on. How could these pairs of items even seem to be different, if they were really just the same?
Of course, it will not do to say that blue is the way a physical property X appears to us, the feeling of nausea is the way a physical property Y appears to us, and so on. That would just introduce ways things appear. But then we would just have to ask how physical properties are related to their ways of appearing. They do not appear as what (according to physicalism) they really are; i.e., they do not appear as complex physical properties. So how, according to physicalism, could it happen that X can appear as blue, but not as complex physical property X, if blue = X?
The new developments reported at the conference that were of most interest to me were attempts by physicalists of ways of dealing with this last question. Here are brief summaries of two key ideas.
A. To be feeling something is nothing other than to record and adjust action in the following ways. (i) Recognize dependence of changes of input to one’s sensory devices upon movement of one’s own body. (ii) Recognize changes of input to one’s sensory devices from sources that do not depend on one’s own body (and distinguish these from the changes in (i)). (iii) Process some parts of input more intensively than others. (When we do this, it is called attending to some aspects of our situation more than others.)
We understand how these features could be instantiated in a robot; so we understand how we could make a robot – a purely physical thing – that feels.
B. What is in the world is all physical. Experienced qualities like blue and the feeling of nausea are not in the world – they are its “form”, not its “content”. So, there is no question of “relating” experienced qualities to what is in the world – in fact, it is misleading to speak of “experienced qualities” at all, since that phrase suggests (falsely, on this view) they are something that is in the world.
It’s time for disclosure: I am a dualist. Not surprisingly, I didn’t find either of these efforts to offer a good solution to what I see as the key problem for physicalism. I’ve done my best to represent A. and B. fairly, but you should, of course, remember that what you’re getting here is what a dualist has been able to make of physicalists’ efforts.