Saturday, March 28, 2009

Mary's knowledge of red

Take Jackson's story: Mary is raised in a black and white setting, never experiencing red. She learns all there is to know about the physical constitution of the world. She leaves her black and white setting. She sees something red. She then comes to know something about the world which she didn't know before: she learns something about the experiences that other people have had. Hence the knowledge about the physical constitution of the world doesn't exhaust the possible knowledge about the world. Hence, the world is more than physical.

The standard objection to this is that this equivocates on "knowledge". Mary gains an ability, an ability to recognize and imagine red experience, say, after coming out of the black and white setting. Jackson has a rather nice answer to this, though. He supposes that Mary, after coming out of the room, toys with scepticism about other minds. But then she rejects the scepticism. In rejecting the scepticism, she does not gain any know-how. But she does gain the knowledge that others have that kind of experience, which she now has when she is looking at a tomato.

Here is a response to Jackson that has occurred to me. If Mary, before she saw red, really knew all there was about the physical world, she also knew that she will come out of her black and white setting, and that she will experience red. Before she has experience red, she can prospectively refer to that experience of red, the experience that she knows she will have (she can use "that" to ostend to that experience she will have). She also already knows that other people have had that experience. When she first sees red, she now "knows what that experience is like." But the only relevant fact in the vicinity, the fact that others have that experience, is a fact that she already knew. She now has a new way of pointing to "that experience" of hers: she can point to it introspectively, while before she could only point to it verbally ("dthat experience which I will have at t7 upon looking at a tomato"). When she toys with scepticism about other minds, she temporarily loses the belief that others have that experience, and then she regains that belief when she rejects the scepticism. So Jackson is right in thinking that Mary loses something that isn't just know-how through scepticism and regain it. But perhaps he is wrong that what Mary loses through scepticism is what she learned about the experiences of others when she saw red. What she learned by seeing red stays there—it's just a new ability to refer to an experience of hers. What she loses is a belief that doesn't bother a physicalist.

I don't know whether the response stands up. I think it depends on the synonymy relations between indexical sentences. If I stand near near x and say "This is a tetrahedron" and you stand far from x and say "That is a tetrahedron", have we said the same thing? (Or, better yet, we both say "This is a tetrahedron", but your "This" gains reference through your pointing with your eyes, and my "This" gains reference through my pointing with my nose (with me closed-eyedly smelling the tetrahedron).) If so, then I think the response to Jackson goes through—we just have two different ways of fixing an indexical. If not, then it needs more work. But even so, if the difference between what Mary knew before she saw red and after she saw red is like the difference between a "this" belief and a "that" belief about something, it might not be a difference that should bother a physicalist.

14 comments:

N. N. said...

She learns all there is to know about the physical constitution of the world.

This, it seems to me, is the part of the story that needs to be rejected. Red is part of the physical world; therefore, if Mary hasn't seen red, she hasn't learned all there is to know about the physical world.

larryniven said...

Right - it also seems incredibly strange to say that she knows everything about the physical world and yet is skeptical about other minds. If minds are physical, she couldn't possibly have such skepticism; if minds aren't physical, it doesn't seem like learning all the physical facts about the world would induce skepticism any more than credulity. So I'm in agreement w/ NN, I think.

Beancan Tatterpants said...

@ N.N. The story is that she learns all physical properties of the real world. One can easily do that without actually having experienced the color red for one's self. She understands everything there is to know about the physical process of light hitting an object, traveling to the eye, and being interpreted by the brain. She just hasn't experienced that herself.

This and Nagel's bat-work are similar in that they point out the disconnect between what's scientifically happening and how the mind perceives.

All that's missing is the cipher between two codes: "625 nanometers" converted to "the richness of the color red." It's two languages without a translator, which is what makes it seem like they are two separate things that Mary learns.

So...I guess I'm a fan of the Acquaintance hypothesis. She already knows red, she's just getting acquainted with it in a new way.

N. N. said...

The story is that she learns all physical properties of the real world. One can easily do that without actually having experienced the color red for one's self.

That's what I'm denying. The color red is a physical property. Physicalists should stop being representationalists and reductionists.

To the simple questions: 'Where is red?' and 'What is red?' the answers are not 'Inside the skull' and 'A frequency of electro-magnetic radiation.' Red (like any other 'sensory' property) is 'in the world,' e.g., it's apples that are red. And that doesn't mean that apples reflect a certain frequency of electro-magnetic radiation. Red is a macro-property of the apple that cannot be reduced to any other physical property.

There are good reasons to accept both of these claims. If red is 'in the skull,' then we're saddled with all the epistemological problems that come with representationalism. And if red just is radiation, we're going to be forced into making nonsensical claims such as 'Such and such a frequency of electro-magnetic radiation is darker than pink' (the terms are not substitutable salve significatione, i.e., replacing a meaningful occurrence of 'red' with an expression concerning radiation results in nonsense).

N. N. said...

For further explanation of my last comment, see my post here.

Alexander R Pruss said...

N.N.:

She hasn't seen red, but why does one need to see something to know it?

Larry:

I guess the way to think of the skepticism hypothesis is that she knows everything about the physical. But then the skeptical worries overcome her for a while. During that while, she doesn't know everything about the physical.

BT:

I think my proposal is a way of expanding on the acquaintance view.

N. N. said...

@ Pruss,

She hasn't seen red, but why does one need to see something to know it?

How else would she know what red is?

Knowing what red is is equivalent to knowing what 'red' means. The primary definition of 'red' is the ostensive one: 'That color is red.'

Alexander R Pruss said...

Why can't she ostensively define "red" as "the color of a (standard) ripe tomato, of the stripes and leaf in the Canadian flag, etc."? Or even: "The color of that experience which I will have when I step out of the room and see a ripe tomato for the first time." The latter shows that before she has seen red, she can ostensively define red in terms of the very same experience in terms of which she can ostensively define red after she has seen red.

N. N. said...

Why can't she ostensively define "red" as "the color of a (standard) ripe tomato, of the stripes and leaf in the Canadian flag, etc."? Or even: "The color of that experience which I will have when I step out of the room and see a ripe tomato for the first time."

I think your last example shows that we mean different things by "ostensive" definition. An ostensive definition requires a sample. An ostensive definition of red, for example, cannot be given in without a sample of the color red (whether it be the red of an apple, flag, etc.).

Mary could be given the definition 'Red is the color of a ripe tomato.' But if she'd never seen a ripe tomato, this definition would be vacuous at just the point at which it is supposed to be informative, viz., the color. Simply put, Mary cannot know what red is, if she's never seen red. The same goes for any occurrence of red as the color of a tomato, flag, fire engine, etc.

Alexander R Pruss said...

But Mary has available to her lots of samples. There is the sample in the future which she will experience. There are present samples which other people are experiencing.

It doesn't seem right to require for an ostensive definition that one be actually perceiving, or have perceived, a sample. If I know that in the middle of a room there is a large mammal, I can go into the room with eyes covered, and point to the middle of the room, and say: "I will call that an 'elephant'." That is sufficient to establish the meaning of "elephant". It does not, of course, give me any understanding of what elephants are, but ostensive definitions tend not to give much understanding.

N. N. said...

Pruss: If I know that in the middle of a room there is a large mammal, I can go into the room with eyes covered, and point to the middle of the room, and say: "I will call that an 'elephant'." That is sufficient to establish the meaning of "elephant".

Establish it for whom? Perhaps for someone else, if there happened to be someone else in the room, but not for you. You are no closer to knowing the meaning of 'elephant,' i.e., to knowing what an elephant is.

Alexander R Pruss said...

Well, it's certainly enough to fix the reference. Is it enough to fix the meaning? I think so. After all, whether I see the elephant or not, I am pointing to one and the same thing. It is true that I do not know much about the elephant if that's all I'm doing--I just know it's an enmattered object in the middle of the room. But this isn't that different from other ostensive definitions. I point to a sample of water and say "That's water." I've defined "water" successfully. But what do I really know about water? That it shimmers and that it's there. The shimmering seems to tell me very little about its nature. So if I point to a sample of water with my eyes closed and say "That's water", I surely still manage to fix the meaning.

OK, but maybe there is a gap between fixing (=establishing) the meaning and understanding the meaning. Maybe I can fix the meaning without understanding it. And maybe that's your point?

If so, then it seems that an argument is owed as to why there is more to understanding what red is than understanding that it is the color that things have when they reflect light of certain wavelengths in normal conditions, and that it is the color that certain ostensively specified experiences (of one's future self or of others' present selves) are experiences of.

N. N. said...

Pruss: Well, it's certainly enough to fix the reference. Is it enough to fix the meaning? I think so. After all, whether I see the elephant or not, I am pointing to one and the same thing.

Again, fix it for whom? If you can't see what you're pointing at, then you're certainly not fixing the reference or the meaning for yourself. If, for example, you were taken to the zoo you would be completely unable to point at (or describe) an elephant. What, then, has been gained by the initial 'definition'? Nothing.

An argument is owed as to why there is more to understanding what red is than understanding that it is the color that things have when they reflect light of certain wavelengths in normal conditions.

Follow the link I give above in my follow-up response to 'Beancan.' The argument is basically that the meaning of 'red' (which, in large measure, is constituted by the ostensive definition of 'red') cannot be synonymous with the meaning of '[The relevant frequency] of electromagnetic radiation.' These expressions belong to different logical categories, and therefore, cannot have the same meaning. And if they cannot have the same meaning, red cannot be identical with a certain frequency of electromagnetic radiation.

Generally, I am objecting to the reductionism and representationalism that are implicit in the Mary example.

Alexander R Pruss said...

To fix the reference (as opposed to the sense) of a term, all that we need to do is to give a condition that the referrent and only the referrent satisfies. Pointing to the elephant in a way that is unambiguous does that, even if one doesn't see what one is pointing that. Likewise, even if colors do not reduce to wavelengths of light, there is only one color that corresponds to the "red" range of wavelengths, and so we can fix the reference of "red" in temrs of that.

Whether fixing the reference is enough for fixing the meaning here is the more difficult question.