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|Thu, 19 Mar 2009
Think about your conscious experience as it is right now - everything that's going on in your inner mental world.
Now imagine the items in that world (sights, sounds, thoughts, the feeling of time passing, and so forth) disappearing one by one, until there's nothing left.
The result is a totally blank inner world - a mental world with no impressions or other contents at all.
What is left over? Just your consciousness - a "pure" consciousness, with no contents.
Now ask yourself a question: Is this any different from no consciousness at all?
What is the difference between a completely empty consciousness and no consciousness? Is there a difference?
This mind-bending question might seem purely theoretical. After all, how often does anyone have a pure, empty consciousness? Perhaps this happens sometimes during states near to unconsciousness, or during deep meditation - or perhaps not. In either case, empty consciousness seems to have little to do with our ordinary mental lives.
If you think about it further, the question of empty consciousness turns out to be important. This question might bear on the puzzle of the mind-brain relationship. Here's why.
If an empty consciousness is not possible, then the absence of conscious experience - the lack of a "stream" of impressions and other mental contents - is the absence of consciousness itself. If (as we usually suppose) the brain is responsible for creating these contents, then consciousness is entirely dependent on the brain.
On the other hand, if an empty consciousness is possible, then the absence of conscious experience might not spell the complete absence of consciousness. All the contents caused by brain activity could stop for a while, and some residue of consciousness - an empty consciousness - would remain. This empty consciousness would exist without any of the contents that correspond to brain activity. This raises the possibility that consciousness itself, in the form of an empty consciousness, might exist even in the absence of brain activity. In other words, maybe the mind is not simply reducible to the brain.
It is hard to see how scientific evidence could rule out this possibility. We can use scientific observations to study behavior, mental activity, and the processing of information in the brain. However, it is hard to imagine how science could test for the existence of a hypothetical "pure" consciousness in which no mental events happen. Suppose that a comatose person or a really good meditator were truly devoid of mental contents for a while. What observations would you do to tell whether this person was truly nonconscious or was in a state of empty, contentless consciousness? No set of scientific observations could tell the difference. Science studies consciousness by collecting and interpreting data about behavior (including verbal reports) and the functioning of the nervous system. The absence of behavior, and of the kind of brain activity associated with experiences, would point to the absence of any impressions, thoughts, feelings, or the like - any contents. However, if there were an empty consciousness, it would not be associated with any impressions or experiences. There is no compelling reason to expect that such a consciousness would be evidenced by any behaviors, or by any happenings at all. To use a colloquial English phrase, such a consciousness would be "nothing doing." Even if there were some type of observable brain activity associated with empty consciousness, how could a scientist decide whether this activity is associated with empty consciousness or with nonconsciousness? The subject would behave the same way in either case. From a first-person standpoint, neither empty consciousness nor nonconsciousness would involve any distinguishable experiences, so the subject would not have any grounds for making different reports. Thus, the question of the existence of an empty consciousness does not seem to be an empirical question at all.
Why should we even worry about empty consciousness? It seems like an outlandish possibility - the stuff of thought experiments at best. So why worry about this possibility? One potential answer comes from the strange world of mathematical logic. If we apply a little formal logic to the question of empty consciousness, we find that empty consciousness might have to exist, even if science cannot decide its existence one way or the other!
The most striking feature of consciousness is the existence of a way things seem - an "inner world" of facts that seem, to the conscious subject, to be true. If you are conscious right now, things seem a certain way to you. This "way things seem" is different from the objective, external world in many ways. Things can seem to be the case that are not the case (as when illusions occur), and many things really are the case that do not seem to anyone to be the case. The important fact is that there is a way things seem. For any conscious subject, a fact may seem to be the case or may not seem to be the case. These "subjective facts" of an observer's consciousness can be quite different from the facts of the objective world.
If you are conscious, you have a world of subjective facts. A "conscious" system that does not have such a world is not really conscious at all.
In my book From Brain to Cosmos, I used ideas from modern logic to explore the idea of subjective fact. I stressed the fact that consciousness defines what logicians call a modality.
The idea of a modality is somewhat involved. To show what a modality is like, I'll present two examples of modalities. (For more information, see a book or encyclopedia article on modal logic.)
Example 1: Possibility. Given any statement, you can create a new statement by adding the words "It is possible that" to the beginning of the statement. The new statement then describes what is possible instead of what is actual. For example, you could begin with the statement "There is a zebra in Moscow." From this you can form a new statement: "It is possible that there is a zebra in Moscow." This statement describes what is possible - what might possibly be true. This statement can be true even if there actually is no zebra in Moscow. After all, the mere fact that there is no zebra in Moscow doesn't rule out the possibility that a zebra might end up there!
The phrase "It is possible that" stands for an important modality - the modality of possibility. (Philosophers recognize several different kinds of possibility, but I won't explore those details here.)
Example 2. Pastness. For any statement, you can make a new statement by adding the words "It was the case that" to the statement. The new statement then describes what was true in the past, instead of what is true now. For example, you could begin with the statement "There is a zebra in Moscow." From this you can form a new statement: "It was the case that there is a zebra in Moscow." A less awkward and more grammatical way of saying this is: "There was a zebra in Moscow." This statement describes what was true in the past. This statement might be true even if today there is no zebra in Moscow. If today there is no zebra in Moscow, this doesn't rule out there having been a zebra in Moscow in the past!
The phrase "It was the case that" stands for an important modality - the modality of pastness. (Philosophers also recognize several other modalities having to do with time. The mathematical subject of "tense logic" makes use of these modalities.)
These two examples illustrate what a modality is. It's like a function that changes a statement into a statement of a different kind. Phrases like "It is possible that" and "It was the case that" change ordinary statements about the actual, present world into statement of other kinds - statements about possibilities and about the past, respectively. You can think of a modality as a way in which propositions can be true. A proposition (like the proposition that there is a zebra in Moscow) might be actually true - but it also might be possibly true, or true in the past. Even a proposition that isn't actually true can be "true" in one of these other ways.
Students of logic know of many different modalities. For our purposes here, the important thing is that seeming is a modality. The phrase "It seems to me now that" changes a statement about how things are into a statement about how things seem. If I say "It seems to me now that there is a blue door," I am making a statement about how things seem to me now - in other words, about my experience. This statement does not imply that there really is a blue door. Maybe I'm looking at a window and misinterpreting it as a door, or maybe I'm only dreaming about a blue door. Or maybe I really am seeing a blue door. In any of these cases, it seems to me that there is a blue door.
Now, what does all this talk of modalities have to do with the problem of empty consciousness?
Suppose that you really did attain a period of empty consciousness, like I described earlier. Would there be anything of your consciousness left over during that period?
Yes, there would. Even if you were having no experiences, there still would be a modality of seeming. There would be the modality of how things seem to you now - and this modality is an important element of your consciousness!
At any given moment during your period of empty consciousness, there still would be the modality of seeming to be the case for you now. This modality, like all modalities, is a way that propositions can be true. Even if there currently are no propositions that are true in this way (that is, nothing seems to be the case for you now), there still is this modality of seeming to be the case for you now. We still can make meaningful statements using this modality, even if nothing seems like anything to you. At very least, we can make the statement "It is not the case that it seems to you now that P," where P is any proposition at all. (Translation of this statement into plain English: "Nothing seems like anything to you now.") If you are conscious of nothing at all, then the statement "It is not the case that it seems to you now that P" is true, and describes an actual state of affairs. The statement could not be true in this way if the phrase "It seems to you now that" were meaningless. We know what this phrase means; it means the same as it meant before you went blank! Since that phrase still has its meaning, it follows that there still is a modality of seeming to be the case for you.
The bottom line is that there is something left of your consciousness even if your consciousness is absolutely empty! This "something" is a modality of seeming - a modality that is essential to being conscious. Even if you are not conscious of anything, there still is such a modality.
Of course, the modality is not an extra thing that exists besides your brain activity. The modality isn't a "thing" at all. It's an abstract logical item, just as are the other modalities like possibility and pastness. The important fact is that the modality of seeming does not go away just because your consciousness is empty. It continues being what it was before: just a modality.
Now we can answer the question that started this post. Is there any difference between an empty consciousness and no consciousness at all? Yes, there is! With an empty consciousness, there still is a modality of seeming, similar to the one that the conscious subject used to have when his/her/its consciousness was not empty. This applies to a subject whose consciousness didn't used to be empty, but is empty now. This situation is very different from the existence of no consciousness at all. If a physical system (like a rock) has no consciousness at all, then there is no modality of seeming associated with that system. There simply is no way that things seem for that object - not even an empty, blank, void way.
The fact that seeming is a modality suggests that there can, in principle, be an empty consciousness. There is no fundamental logical reason why an empty consciousness of some kind cannot exist. This is true because there is more to consciousness than just the contents of experience. There also is the modality of seeming - which is equally real whether or not consciousness has any contents.
Earlier I pointed out that if empty consciousness is possible, then consciousness has a feature that science cannot detect. Since empty consciousness is possible in principle, we are stuck with an interesting conclusion: that there is at least one fact about consciousness that science cannot know. This conclusion may seem dangerous to the scientific approach to nature, but actually it is not dangerous at all. Mathematics constantly deals with facts beyond the reach of scientific methods - for example, the fact that the Pythagorean theorem follows from the axioms and postulates of plane geometry. No one thinks that such formal mathematical facts are threats to science. The existence of an untestable feature of consciousness is a fact of much the same sort. It is a formal fact that becomes apparent when we apply modal logic (a type of mathematics) to the idea of consciousness. The facts of mathematics and logic are not threats to science - so the fact that empty consciousness is possible cannot be much of a threat either!
(Post updated slightly 10/18/2010 - one link changed)
posted at: 21:48 | path: /mind | persistent link to this entry
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