Philosophy
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LECTUREThequaliaproblemandNagelsbatargument.docx5
LECTURE: The qualia problem and Nagel’s “bat” argument
The qualia problem
Recall that at the beginning of the semester, we distinguished three key aspects of the mind that have been thought to pose problems for materialism: rationality, qualia, and intentionality. We’ve now looked at the main way that materialists have tried to explain rationality, which is in terms of the idea that the mind is a kind of computer software. We’ve also seen how thinkers like Searle have criticized this theory.
We want to turn now to a closer look at the second of these aspects of the mind: qualia, which are the defining “first-person” aspects of conscious awareness. Examples would be the way a color looks, the way pain feels, or the way a ringing in the ears sounds. Anyone could in principle examine what is going on in your body and brain. But nobody but you has direct access to your qualia. So how could qualia be identified with any physical aspect of the body or brain? That, you’ll recall, is the heart of the qualia problem facing materialism. It’s the problem of showing how qualia can be explained in materialist terms, despite appearances.
It is often assumed that consciousness and qualia will inevitably be explained by science in more or less the same way that science explains other aspects of nature (such as motion, temperature, solidity, etc.), namely by reducing it to the behavior of micro-level physical entities (such as particles of various kinds) governed by physical laws (the laws of physics, the laws of chemistry, etc.).
However, several thinkers have argued that there is a serious problem with this assumption, a problem that derives from the nature of scientific explanation itself. On their view, modern science limits itself to a mode of explanation that makes a complete scientific explanation of consciousness impossible even in theory. Contemporary philosopher Thomas Nagel (pictured below) has presented an argument to this effect, in his very influential article “What is it Like to Be a Bat?” What is the argument? And why would he ask such a bizarre question?
What is it like to be a famous philosophy professor?
Subjective versus objective
Nagel’s argument starts with a distinction between “objective” and “subjective,” terms which he uses in a very specific technical way. Features of the world are objective when they are what they are completely independently of the point of view of any observer. For example, the speed at which the molecules in a bucket of water are moving around is an objective matter. It is what it is whether anyone is looking at the bucket or otherwise observing it. Whether photons are bouncing off the surface of a certain red apple is also an objective matter in this sense. They are doing so whether or not anyone is there to perceive the apple.
Features are subjective when they are not independent of the point of view of every observer, but are instead inherently tied to the observer’s point of view. For example, whether the water in a certain bucket has a hot or cold feel to it depends on the observer. If Alan is soaking his hand in a bucket of hot water and Alice is soaking her hand in a bucket of cold water, and they each then stick their hands in a bucket of lukewarm water, it will feel cool to Alan and warm to Alice. If Alan is colorblind and Alice is not, then the way the red of the apple looks to Alan is going to be very different from the way it looks to Alice.
In general, facts about conscious experience – about what it is like to see red, what it is like to feel heat, what it is like to have a headache, what it is like to hear a noise, etc. – are subjective in this sense. Notice that this does not mean that they are somehow “touchy feely” or unreal or anything like that. It is a fact that the lukewarm bucket really does feel cool to Alan, and it is a fact that the apple really does look bright red to Alice. The point is just that these kinds of facts are tied to the point of view of the observer. You’d have to get into Alan’s consciousness to know facts about what color and temperature seem like to him, and similarly for Alice. But of course, you can’t get into anyone else’s consciousness – you have access only to your own.
Is the dress gold or blue? It’s subjective, in Nagel’s sense.
Now, physical facts, as modern science understands them, are objective rather than subjective. Indeed, Nagel points out that that is essentially how modern science defines what it will count as “physical.” What is physical is taken to be essentially what would exist in the absence of any observer. What is physical is what would be there even if there was no conscious awareness.
Scientific explanation
The next point Nagel makes has to do with the way a reductive scientific explanation works. It works by taking some phenomenon, stripping away every aspect of it that reflects the point of view of the observer, and re-defining the phenomenon in terms of facts that would remain as they are entirely apart from any observer. In other words, it involves defining the thing being explained entirely in objective terms and ignoring anything subjective (in Nagel’s technical sense of “subjective”).
So, consider temperature, for example. Modern science essentially defines the temperature of the water in terms of molecular motion (to oversimplify a bit). It does not treat the feel of heat or cold as reflecting anything really there in the water. That part is only in the mind of the observer. What is physically real in the water is just what would stay the same regardless of whether anyone is observing it, and that would just be the motion of the molecules.
Something similar can be said of color. Science defines color in terms of what would remain the same regardless of who is looking at an object like an apple. And that would be the tendency of the surface of the object to absorb some wavelengths of light and reflect others. What it is to be “red,” for purposes of physics, is just to have a certain reflectance property of this kind, which an apple has regardless of whether anyone is observing it. The look of red to someone who is not color blind is treated as something that doesn’t correspond to anything really there in the apple itself. It exists only in the mind of the conscious observer, not in physical reality.
Is the suit blue or… burgundy?
What is it like?
But now let’s consider consciousness itself. Consciousness just is the way things seem from the subjective point of view of the observer. So, if the way science explains something is to strip away the subjective point of view of the observer, how could it possibly explain consciousness? It would be stripping away – putting to one side, ignoring – the very thing it is supposed to be explaining!
Another way to put it is that modern science basically defines what is “physical” as what is objective or non-subjective, and defines what exists in consciousness as what is subjective or non-objective. And so, its very method seems to define consciousness as non-physical and thus not the sort of thing that can be given a reductive explanation.
This is not just a matter of arbitrary definitions, though. Another part of Nagel’s point is that it seems to reflect something in the nature of the phenomena themselves. He illustrates this with his example of a bat, which has become famous in discussions about whether science can explain consciousness.
Bats get around by “echolocation,” a kind of sonar sense that isn’t quite seeing and isn’t quite hearing. It’s not the sort of thing we’re capable of. So, suppose we wanted to know what it is like to get around by way of this sense. Suppose we wanted to know what it is like to be a bat. Could science tell us?
Nagel thinks that it could not. It could tell us how a bat’s brain is wired, and how its ears are structured, and other aspects of its anatomy and physiology that allow it to get around by echolocation. But that would not tell us what it is like actually to get around that way, any more than a person who was blind from birth onward would be able to know what it is like to see red just by hearing a description of the structure of the eye, of the optic nerve, and of the brain activity that goes on during visual experience.
To know what it is like to be a bat, you’d actually have to be one. You’d have to get inside the consciousness of the bat, which we can’t do. Facts about the consciousness of a bat are subjective in Nagel’s sense, whereas facts about the bat’s anatomy and physiology are objective. Science can only give us knowledge of the second sort of fact, not the first.
“Why didn’t Nagel ask me?!”
The limits of science
So, in Nagel’s view, on analysis it doesn’t make sense to suppose that science could show that consciousness is really just a physical phenomenon, at least not given how modern science defines “physical.” Perhaps it would be possible to come up with some radically different conception of the “physical” on which this would be possible. But given our current understanding of what is “physical,” he thinks that we don’t really even understand what it would be to explain consciousness in a purely physical way.
We might sum up Nagel’s argument in a step-by-step way as follows:
1. Physical facts are objective in the sense of being independent of any particular point of view.
2. Facts about conscious experience (e.g. facts about what it’s like to be a bat) are subjective in the sense of being tied to a particular point of view.
3. A reductive physical explanation of some phenomenon involves moving away from the way it appears from our point of view and describing it instead in objective terms.
4. But this approach seems to make no sense when applied to conscious experience itself, since in this case the way things appear to us subjectively just is the very phenomenon that needs to be explained.
5. So, we have no conception of what it would be to give a physical explanation of conscious experience.
You might have noticed that Nagel’s point is very similar to one we saw was made by Descartes’ follower, the early modern philosopher Malebranche. Malebranche had argued that if you start with the “mechanical” conception of matter that modern science works with – matter as colorless, odorless, soundless, tasteless particles in motion – then by definition you are going to have to regard color, odor, sound, taste, etc., as common sense understands them, as non-material. Though he doesn’t put it that way, Nagel is essentially making the same point.
Other contemporary philosophers too, including some who are otherwise sympathetic to the materialist project, have made similar points in arguments that have been as influential as Nagel’s. We’ll look at some of them next time.
Susan Blackmore on Nagel, consciousness, and subjectivity:
https://www.youtube.com/watch?v=uPnKn_7eHr4
Jeffrey Kaplan on Nagel’s argument:
https://www.youtube.com/watch?v=aaZbCctlll4
Jeffrey Kaplan on inverted qualia:
https://www.youtube.com/watch?v=UuSv1UbNCGs
Nagel on what it is like to be a bat:
