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?
- Mary knows every physical fact about color perception.
- There's a fact about color perception that Mary learns when she sees red - namely, what it is like to experience seeing that color.
there are more than just physical facts (so materialism is false).
There have been a few traditional ways of resisting this conclusion.
- 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.
- 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.
- 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
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
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.