Teaching: July 2009 Archives

This is the 51st post in my Theories of Knowledge and Reality series. The previous post discussed a different kind of dualism from Descartes' interactionist substance dualism. To avoid objections against Descartes' view, some philosophers propose epiphenomenalist property dualism. They argue for this view based on facts about the first-person perspective that can't be reduced to third-person facts accessible to science. This post looks at Frank Jackson's formal argument for that thesis. 

Consider someone who can discern shades of red better than we can. Show him two tomatoes that look the same color to the rest of us, and he'll be able to see them as two different shades. He will consistently separate the same tomatoes as being red-1 and the others as being red-2, no matter how many times and how well you mix them up again. There's something about his perception of colors that we can never know, even if we know everything about his brain and how it works. There's a fact that remains - what his experience is like for him.

Consider a color scientist named Mary who has never seen red. She lived in a black and white environment with special contact lenses all her life, so she'd never seen most colors.  Then she went on to learn the neuroscience of color perception. She now knows everything there is to know from science about color perception. She knows what color words apply to which wavelengths of light. She knows what goes on in the brain when people see various colors. But she's never seen red. Then she takes off the contact lenses, and someone gives her a tomato. She now sees red for the first time. Does she learn something? Jackson says she does - what it's like to perceive the color red.

  1. Mary knows every physical fact about color perception.
  2. There's a fact about color perception that Mary learns when she sees red - namely, what it is like to experience seeing that color.
  3. Therefore, there are more than just physical facts (so materialism is false).

There have been a few traditional ways of resisting this conclusion.

  1. If materialism is true, maybe we shouldn't expect Mary to learn anything new.  If this is right, we should expect her to see red for the first time and say "Ah! That's exactly what I expected it to look like."  That seems highly implausible.
  2. David Lewis suggests that Mary doesn't learn a new fact but just gains a new ability - how to recognize red from within. She could identify red before in different ways, and she's gained a different way to identify it. It's like learning a new language, only more complicated. You can say the same facts in a different language once you've learned it, but hearing something in German that you already knew in English doesn't mean you've learned a new fact. Some philosophers call this implausible also, since language learning is just translating things we knew into different representations, but this is a totally new experience. There's got to be something more to seeing red than just having a certain ability.
  3. Some have suggested that Mary gains a new concept but doesn't learn anything new. She has a new way to express what she already knew - in terms of color experiences now, whereas before she just had the concepts involved with wavelengths, brain waves, neurons, and human behavior. But is this going to be successful? Mary seems to gain some new knowledge about color perception. Gaining just a concept doesn't seem enough. Something about the new experience seems to suggest more than just gaining a new way to think about something she already knew.

In the end if Jackson is right, you get dualism. You might think it's the best of both worlds. It avoids the simplicity arguments against dualism, since it doesn't require actual things in the world that are non-physical. It just requires some feature of me, a physical being, to be a non-physical property. So the view is called property dualism. The standard dualist view, substance dualism, holds that there is a real thing that's part of me - an immaterial soul or mind. Also, this view avoids conservation law problems. According to our best science, matter and energy can't be created or destroyed. If something comes in from outside the physical  order and interferes, this law would seem to be broken. But property dualism just says there are features of physical things that it wouldn't be right to call physical. The natural order of things continues on as normal. Nothing outside the natural order needs to come in and affect the physical world. So someone can honor dualist intuitions and have a view that's not materialist but seems to avoid the dualist's problems. Some people think they're trying to have their cake and eat it too, but Jackson and Nagel see this as the best of both worlds.

The other way around the Knowledge Argument is to deny the first premise. Mary doesn't really know all the physical facts about color perception. She does know all the impersonal facts, facts you can know independently of experiencing the color through perception. But maybe these experiential facts are still physical facts, just not impersonal ones. This does get out of the argument, but for some reason many materialists don't take this way out. It might be because they see people who take this line as abandoning one of the motivations for being a materialist in the first place. The whole idea was to get a theory according to which you can understand all of reality in scientific terms. That's why we want to avoid dualism, since that goes beyond science. This approach abandons that idea. Science can't capture all the truths, even all the physical truths. The other ways of avoiding Jackson's argument try to hold on to that notion. This one abandons it. It could be right, but as a materialist view it seems less in line with materialism as a whole, since it loses one key reason for being a materialist.

One response to this argument might be that it's not in principle impossible to get all the facts, even first-person ones. We lack the technology, but it seems possible with virtual reality. We could give someone the same brain state as someone else. This might take a lot of work, and it might be difficult to get the person to remember it when  you restore them to their previous brain state, but it seems in principle possible to give one person the same inner feeling another person has, provided we figure out how to manipulate neurons, transform brain matter to match how another person's brain is physically arranged, and so on. It probably wouldn't take changing the whole brain, just the parts necessary for conscious experience. This does rescue at least some of the idea that science can in principle capture all facts about the universe, and any investigator could eventually in principle do what's necessary to know any fact. It would take something far more radical than just what I described above, though. After all, we would have to be able to experience for ourselves what it's like to be a bat, a bee, or any other organism that has conscious experience, even the ones with minimal experience. To get ourselves so that we could do that, we might have to modify our brains so radically that we're not really us anymore, depending on your view of personal identity. So this response has something to say, but it's not clear that it goes all the way.

Another hesitation a materialist might have at this response is that this isn't what people meant by science capturing all the facts about the world. The original idea was to list all the facts resulting from external, third-person investigation, measurable entities you can quantify. If you can't simply list off all the facts, even if you have the potential to have all the possible first-person experiences anything could have, then you can't even in principle give a scientific account of the world in third-person terms. It's that kind of description of the universe that many materialists want science to come up with, and if Jackson is right that these first-person facts are additional facts, that ends up being impossible.

In the next post, I'll look at one further mind-related issue before turning to personal identity: artificial intelligence.

Property Dualism

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This is the 50th post in my Theories of Knowledge and Reality series. The last post looked at the interaction problem, which is raised against the standard form of substance dualism known as interactionism. This post moves to a different form of dualism, property dualism or epiphenomenalism.

According to this view, the physical does cause the mental, but no mental event causes any physical event. The physical world gives rise to mental activity, but there's nothing going the other way. It's sort of like a free rider. Whenever brains are constructed in the right way, thoughts happen. Brains have mental properties, and there's nothing physical about these properties. This view doesn't assume any soul-like mind as a substance. There doesn't have to be any thing that's non-physical. Because of this, the view is often called property dualism (as opposed to substance dualism). This view avoids the problems of interaction (at least the problem with the conservation laws) and the problem of simpler views being more likely, since the mental things don't exist according to property dualism. This view agrees with materialism about which things really exist. The strangest thing about the view is that it's got one feature in common with parallelism - the mental stuff doesn't do anything. Nothing in the world is caused by it. So your thoughts don't affect anything. It's worth thinking about which objections to parallelism also apply here.

The Mutant and Zombie cases to illustrate this view (I believe David Lewis first used the term 'mutant' this way, and David Chalmers seems to be the one who coined the philosophical use of 'zombie' in this way). Mutants are just like normal people physically but have different qualitative experiences. Some of them have their colors reversed. When a color mutant sees what we see as red, she says it's red but sees it the way we see blue. When she sees what we see as yellow, she says it's yellow but sees it the way we see orange. Is there any way we could know that such a thing was going on? Maybe it does occur. There's no way to rule it out. The same sort of thing could go on with the sense of taste (sweet and sour reversed, salty and bitter reversed), sound (high and low pitches reversed), or even touch (soft and hard, rough and smooth). Maybe even pain and pleasure could be reversed, with someone experiencing what we feel as pain but calling it pleasure and smiling, etc. This seems really weird, but if their physical makeup is just as ours, then they would smile and say it's good when they have the same brain state as we do when we experience pleasurable things. Yet maybe their internal feel is totally different. How would we know?

The zombie is someone who just has no internal feel whatsoever. The zombie experiences nothing, but we could never know. How do we know if anyone else even feels anything? They act the way we do when we experience things. They say things. They cry out in pain. They act overjoyed when things go really well for them. They talk about how great certain foods taste. But couldn't it be possible that they are just following a sort of programming? When their brain received certain input, it makes changes within the brain, and some of these affect what the body does as a response. Couldn't that occur without any actual sensation or experience?

Frank Jackson and Thomas Nagel believe both zombies and mutants are possible (though probably not actual). They hold this property dualist view. Their reasoning is that some things about our experience can't be explained in physical terms, so there must be some non-physical properties. They take this from Nagel's case of the impossibility of imagining a bat's experience and Jackson's case of someone knowing every physical fact but still not knowing what red looks like. There's something about the first-person perspective that can't be captured by any third-person understanding of what the world is like in physical terms. That leads them to a kind of dualism, though it doesn't require any soul-like mind. It wouldn't mean there isn't any such thing, but all it requires is mental properties.

One problem with the materialist views is that they seem to leave out an important aspect of mentality - the inner feel of conscious experience. Nagel focuses on the question of what it is like to be a bat - to experience life with such different perceptual input from what we've got. It's something we can never know. Similar, men can never know what it's like for a woman to give birth or to experience the social and biological influences that affect how women think about the possibility of being raped. A white man can never know what it's like to grow up as black in the United States. Someone who has never experienced an orgasm cannot imagine what such an experience is like. Someone who has never been drunk or high doesn't know what that is like. Try imagining seeing a color besides the ones we've experienced. If there is a God and some people have genuine relationships with God, nonbelievers don't know what that experience is like. We can't even imagine going beyond our experience. These are facts about our inner mental life that we simply can't capture in terms that we can communicate to someone else. Facts about the first-person perspective seem to be left out of all the materialist views. Nagel suggests that dualism can capture what's missing.

Jackson gave a formal argument for exactly that thesis. I'll discuss that argument in the next post.

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