 Well today, we're going to have one last look at the main ideas of Putnam's meaning and reference on a Friday we'll move on to Excuse me on Friday. We'll move on to Evans's paper the causal theory of names even just paper is a very very rich paper It's really like more like a book than a paper Every time I read that I find whole discussions. I just never noticed before So it's good to start early on that and Try to make room to read it many times Today, I'm not really going to do a straight Run through the Putnam the thing we haven't covered in the Putnam is his remarks about division of linguistic labor But I'm going to leave that as homework What he says about division of linguistic labor is relatively straightforward And you might agree or not, but it's what he's saying I think it's fairly plain if not, let me know and We may cover it later today what I want to do is take a Look at how causal theories of reference work for a fairly confusing case the case of color Can we regard color words as a subject to a causal theory of reference? So I'm going to try and break this up quite a bit, but I'll start out with Looking at this. This is not meant to be a D daunting blizzard of topics. It's just trying to break this confusing subject up into a lot of bite-sized pieces Okay, so let me start out with just the idea of a causal theory of color representation We've been saying I mean we have these theories in the table You may agree with them or not, but that proper names represent in virtue of a causal connection to the object so the object causes you to use the name and Since there's that causal connection between The object and your use of the name. That's how come the sign refers to that thing. That's okay That's a familiar idea by now You've heard that before Yes Okay, okay Well, am I am I in the right class? Okay, and similarly For words of natural kinds or terms like gold tiger water and so on you might say well There's that stuff out there that is causally impacting on all of us and In response to those causal impacts of the stuff we use the signs the way we do That's how calm those signs refer to those stuffs Yep So how does it go for color? In your color perception you are represent the colors of the objects around you That's all right. You know you look around the room you get all the colors. You're representing the colors of the objects around you So how general is the causal theory of reference? Do the colors the color representations? refer to particular colors in virtue of being caused by those colors out there Well, here's Locke Locke For those of you who are fans is really the prototypical causal theorist of Representation what clearly thinks that ideas in general Represent in virtue of their causal relations to the environment He thinks that this is these things are true for all ideas, but in particular your color experiences are Caused by textures what he calls textures. So that's micro physical structures in the objects around you and What's going on in color perception is that the ideas you have of the colors are Caused by particular textures the the reason God gave you a color perception Locke thinks is that those sensations You are having a reliable signs of particular physical textures in the world out there and therefore The color experience stands for the type of texture that typically causes it causes it I mean nowadays people would talk about evolution and adaptation, but The a conventional story today would be pretty much like that. It would say why did evolution give you color perception? Well because those sensations are reliable signs of the presence of particular micro physical structures in the physical world outside you So in this kind of picture you were in the one hand light of different wavelengths This might be pure. This is for pure spectra light light of different wavelengths, and you get the visible spectrum is just a little bit of it and Those ideas of color that we have are really just responses to light of particular wavelengths More generally you might say something like having a particular color idea is a matter of being sensitive to the ratios of light of different wavelengths being Reflected from various parts of your surroundings So the general picture is really similar to Putnam's thing about water or cookies thing about names You got a texture out there in the world That causes you to have the idea of redness and therefore the idea of redness refers to that texture I mean, it's not quite obvious where the quality of character comes from in this view You've got the quality of characters of the colors up here And they're not how should I say those quality of characters of the colors are not out there in the physical world So it's not quite obvious where they come from What's going on with them? Nonetheless, you do have color sensations that have particular qualities of characteristics And they're representing particular physical textures around you something like that is a picture So you've you've got you've got those I See so it's not quite obvious how this is going to explain How you could have a representation of a qualitative character of a color if you see what I mean I mean the blueness of a blue thing what the intrinsic blueness comes to because that Structure of the wavelengths out there. That's something complex. It doesn't seem to have that Simplicity and unity that the qualitative colors have but anyway, suppose we take this view and we say could there be Twin Earth cases for color and you can make sense of a world where The stuff that fills the rivers and lakes and so on that's not h2o, but xyz that's not water It's something that looks just like water So could you make sense of the idea of a twin earth for color words? And you've got a Causal theory of reference for a sign then the sign refers to whatever's on the other end of the causal chain So all that's going on a twin earth case is that you say well Let's have a world where I get just the same stuff inside my head inside my mind The what's on the other end of the causal chain is something different, right? That makes that that's in general what's going on with the twin earth case. So We could hear how an earth it could be there an hour earth One kind of surface spectral reflectance one kind of physical characteristic is what causes your idea of red But then a twin earth is a quite different physical characteristic of the object that causes the idea of red So if you're transported to twin earth Then everything's going to look just the same But the colors will all be different Even though you can't notice a difference You see what I mean just as if we flip you right now back and forth between earth and twin earth You're not going to notice any difference in the people around you You're not going to notice any difference in the Water around you, but it's still going to be different So you could have that with color, too So red on earth is going to mean the word red is going to be standing for something different to what the word red and twin earth stands for You're not going to notice a difference, but all the colors are swapped around just as the water has been swapped or the people have been swapped So if you have a causal theory of reference for color words It seems like you must have that kind of twin earth scenario must make sense You see that it must make sense in a causal theory Yeah, because just because if you could this kind of picture then you could swap around what the texture is What what the physical characteristic is that you are picking up on? Well one last way to put the point is if you remember this Isaac the shave a singer story about the man who returns to his own village without realizing that he has It makes perfect sense for this guy I mean you sympathize with this plight right, but it makes perfect sense for him to say You look just like my wife You look just like my friend. He might even remark on the similarity, but for him to say but there's not the same people and Similarly, he can look at the animals in the paddock and say these look just like horses But are they horses? So if this is right, then you could do that for colors, too You could say look the colors in this village Look just like the colors in my home village, but maybe they're all different Maybe the colors here are just different to the colors back home I mean this is a fictional story, but there are clinical patients who Have a syndrome kind of like this I don't mean for the colors particularly, but it's kind of the opposite of deja vu They come home from the hospital and they say my god. This is astonishing. It looks exactly like my apartment This looks exactly like my wife, but it's not it's palpably not and they will even comment on how Stunning how unexpected the similarity is between this apartment and their own apartment or this woman and their wife But they will still insist that they're different so Could you have this for color, too? That you have someone who says look at all the colors here They look exactly like regular red and blue They look exactly like ordinary green, but It's obviously not just not the same color If you've got a causal theory of reference for colors, then that should be possible okay That's what you have to be saying if you've a causal theory of reference for colors Plain enough. I'm just curious. Does that sound right? Can you put your hand up if that sounds right? If you think there can be a twin earth for colors, can you put your hand up if you think that sounds wrong? There can be a twin earth for colors Can you put your hand up if you're not quite clear what the issue is? Okay, I mean I'm not noting Okay, but you're quite clear what the issue is, but you're just not sure what the answer is Is it for your hand of that's the situation? I say I'm glad to see that GSIs are in the second situation The usual layer of deep suspicion This is some kind of trick, right? Yes No round the other way on earth and to an earth Just as on earth and to an earth for water they say water and we say water Yeah, but the stuff that their word stands for is different to the stuff that our word stands for the words mean different things Yeah, so similarly on earth and into an earth on this scenario the ward Red and red are used just the same. I mean they seem just the same in everyday life, but um Our word stands for one kind of physical structure and their word stands for a different kind of physical structure So the words mean different things Even though there's some sense in which everything looks just the same Yeah, you wouldn't notice if you were swapped back and forth between there and here Yep Yes, yes That's right. The color percent. There's some sense in which the color perception you have is phenomenologically indistinguishable. You couldn't tell That's right. The stuff out there is different Yeah So I wrote it down. I think yeah So your idea of red you're getting the idea in the in the two situations But this thing out there that's causing it is different Yeah Okay, is that clear what is that clear to inherit what the scenario is what the issue is? okay, I I Just wanted to try and get a fix in this question Because I think this is extremely confusing I think Russell articulated one idea about colors when he said I know the color Perfectly and completely when I see it and no further knowledge of it itself is even theoretically possible And you can see what he means there that if you know about red just by looking at it If you could learn as much as you liked about red in a theoretical kind of way But when you look at the color for the first time you get some kind of knowledge You get knowledge of which particular color that is and That kind of knowledge of which particular color it is you could supplement it by getting knowledge about what kind of wavelengths are associated with it What kind of plants have it what its significance is but How should I say these are knowledge that's knowledge of truth about the color Knowledge of what the color itself is when you encounter it in experience that there's some sense in which that's comprehensive There is nothing more to know about which color red is then you all have just by looking at something red That's what he's saying. I know the color perfectly and completely when I see it No further knowledge of it itself is even theoretically possible now if that picture is right then You couldn't have a to an earth scenario the way I was describing because Your authoritative about when you're getting the same color again when you move from earth on earth You know exactly which color it is red is just by looking Your vision vision just tells you exactly which color it is you got this perfect comprehensive knowledge So then over in twin earth if you're swapped to twin earth when you look at the colors of the objects around you Then just by looking at them you have perfect comprehensive knowledge of which colors these are so of course you can tell Authoritatively whether they're the same you're authoritative about whether over such a thing as red And you know when you're getting the same color again You're not vulnerable to error on this kind of picture so in Russell's account and Your authoritative about whether the colors exist and about whether the colors in one region are the same as the colors in another region It's not like that for natural kinds. It's not what I mean We don't come and sensically think it's like that for terms like water or gold or tiger Nobody in their senses would say I know the nature of water Perfectly and completely when I see it and no further knowledge of it itself. It is even theoretically possible. I mean If that was true, if only it were true, but if that were true then chemistry would of course be a complete waste of I mean No cheap cracks place Chemistry would be a complete waste of time Right because that's what the chemist think they're doing They're finding out about what water or gold or whatever or the zoologist think they're finding about what tigers are They're getting a better fix than common sense has on what these things are So none of us usually would think we have perfect and complete knowledge of these chemical substances You can find out about the structure that's causing your experiences, but in the case of color Russell's thing is at any rate a little bit intuitive. Look, I'll tell you what red is I mean, you can find out about what a company is red, but red itself. I know about I know completely about already That's what Russell is saying but if you have locks kind of causal theory view of the way a word like red works then Locke is saying that colors are really like the way Putnam talks about tigers or water or gold So lock on color is very like Putnam and natural kinds logs and got the same kind of causal theory color perceptions represent the textures of the objects that cause them and the words for the colors are arbitrarily associated with perceptual signs of colors the particular color experiences So of course it's possible to find out more about what color in itself is Now there's something in this view of locks on this causal theory of our words for colors That you've got to get the qualitative characteristic the blueness of the blue thing in Somewhere but in this kind of picture. It's really the color sensation. That's got the qualitative character That qualitative character doesn't seem to be something out there in the world. It's something inside you So in logs view the colors as character come colors as we ordinarily talk about them are in characteristics of sensations their characteristics of objects and in this view Color experience doesn't give you any insight into the nature of the colors Your ordinary experience of water gold tigers and so on doesn't give you any insight into their natures It just gives you a the clue that there is a phenomenon out there to find out about So that's similar with color locks in You don't it doesn't give you any insight. It just tips you off There's a phenomenon there that maybe science will one day tell us something more about That's pursuing this line this causal theory of reference for color terms, okay I Would just like to keep tabs on how you guys out how striking you guys at this point Well, what is your view? So Russia? There's Russell's view color experience tells you what the colors are There's locks view color experience gives you no insight into what the colors are. I would really like to know a vote I mean, what's your hunch does color experience give you insight into what the colors are Can you put your hand up if you if you feel it does? And if you reckon color experience does not give you insight into what the colors are Okay You can turn that into a question It's a strange question. Yes. Yes, right, right The way you describe the way you're describing it is a very good analogy for the way Locke is thinking of it, right? so that's exactly an analogy with This kind of picture so here you have here you have the pen Here you have the sensation of pen. Yeah You stick the pen in you get the sensation of pain does the sensation of pain give you any insight to the needle? No Right, that's that's your point It gives you insight into the sensation itself. Yeah, but when we talk about the colors When you say that one's orange or that one's brown or whatever you're talking about a physical object and describing colors to it So we're talking here about colors as characteristics of physical objects. Yeah, and The idea is that that sensation is not giving you any insight into color as a characteristic of the physical object Yeah, whether it gives you any insight into the nature of the sensation is a further question in the case of pain It is really very plausible that when you have a pain you get some insight into the nature of pain We'll come on to this in a second, but having a color sensation It's not like getting a pain Because how should I say it's not really not that the object kind of jabs me and I go That sensation again. I'm getting that sensation again I wonder what's out there and when you get a pain sensation you can say that really hurt I wonder what's out there. Yeah, when you get color experience the color experience. I Don't quite how to I don't quite know how to put this competently But the color experience seems to be telling you about what the world's like out there You see what I mean is that with a sense of pain sensation Anybody would think it's just giving me information about what's inside my head a color experience seems to it seems to be round The other way it seems to be telling you about what's out there not about what's inside your head Yeah, so but the analogies are very helpful one actually. Yeah one two Do this again if you're someone congenit or someone born blind Right, they're not going to know Yeah, I do that's very good. Okay, let me try that a different way I hadn't thought of putting it like this, but I think let me try playing back your comment to you and see if I'm getting this and This is the causal theory stated right so the texture out there is causing you to have the idea of redness So your idea of redness is representing that texture. That's what the color is. Yeah, so if that's right Then someone born blind should be able to find out about that texture They should be able to know what all the colors are Yeah, it should be possible for someone born blind to know what redness greenness and yellowness all are Because they can find out about those textures Common sense, okay, that sounds a little bit peculiar. Yeah, because you would ordinarily think well That's the last thing someone born blind is going to know about. Yeah, I mean Locke has this example of One of his learned group who was born blind who? Said of course he could figure out what scarlet was and after Some research said tis like the sound of a trumpet to you know great derision That you think we can't know what scarlet is but in this picture he could perfectly well know what scarlet is Whereas with pain It's very common sense of color if you don't have the sensation, but you don't know what it is Yeah, whereas in this causal theory, you could not have the sensation. There's still no perfectly well what the phenomenon is Yeah, is it's up. Okay. No, that's a very good way of getting at what? It doesn't sound quite right. You see what I mean about the causal theory one Cause it being causally affected by something and then how you know the joy Very good. Yeah Is a is a great question. I'm not sure I have a concise answer. Yeah There is some connection between causation and knowledge We'll actually discuss this in connection with Evans more length But let me try and make some brief remarks now There is some connection between causation and knowledge. Yeah, how about that? well Let me let me Let me give an example of a kind philosopher's love Suppose you have a tomato and Suppose you have here a mirror and Suppose you have here another tomato and this is you I'm not drawing this exactly to scale you understand, but this is you looking in the mirror right and so light rays So as is usual in these philosophical examples, you can't see the mirror I mean, you don't know the mirror is there, right? It's a really good highly polished mirror That all right so far So in reflected in the mirror is a tomato which looks to be at exactly the place Where this is if you see what I mean Have I lost you is that too complex? You see what I mean? It's not quite to scale, but this tomato is going to look something like double that distance in this direction You see what I mean? It's going to look like it's exactly at this place That's all right. Yeah, okay, so there's a causal chain here from this tomato to your eyes But there is no causal chain from this tomato to your eyes Yes now here Is the question Which tomato do you have knowledge of if we call this one tomato a and we call this one tomato B Do you have knowledge of tomato a or do you have knowledge of tomato B or neither or both? Yes You were voting You vote for B Anyone else vote for B or is this an outlier? How many people would vote for B? This is not a trick Okay, how many would vote for a Nobody would vote for a not not a single word for a well, of course, that's right. I mean this is really isn't a trick I mean, how could you have knowledge of a right? But what you're assuming there is that there's a connect between causation and knowledge. I The only difference I set out in the example between a and B is that there's no causal connection between a and you And there is a causal connection between B and you Yeah, so causal connections are something to do with knowledge the kind of causal connect that you stand into some external phenomenon Like a person or a substance or a color can be a causal connect that generates knowledge of that thing This needs a lot more discussion, of course, but I just Yeah, this is just to say what the intuitive connect is. Yeah Yeah, okay. Okay. I Listen important moves. Let me just pause now for a moment. So suppose you say well is it is the important thing is not knowledge It's perception Do you see to map here are two questions? Do you see tomato a? Do you see tomato B? Can you think your hand up if you feel that you see tomato a you see tomato I Let me not lead you let me not allow you to persist an error tomato a is completely hidden from you by the mirror Tomato a is behind the mirror, right? If you took tomato a away, you wouldn't even notice so On that understanding Does anyone wish to persist in saying that you see tomato a? And how about seeing tomato B? Yes, of course you see tomorrow be you see tomorrow be in the mirror, right? Yes, okay, so even if you say it's perception. Well, that's fine, but perception so depends on causation, too I'm going to argue against that in a moment. So Let me pause that and get come back to that at the end of when we've done that. Yeah, okay Let's one. What would be the kind of thing that you could know more about the color? Yes, how does he know that there's nothing more to know based on observation? Well, yeah that I Should I put this the Supposed you take the case of pain of an inner sensation of your headache. Yeah, there's the way the pain feels Yeah, is there anything more to know about the pain itself than you are encountering when you have the headache I Mean I think it's very intuitive that all there is to the pain is how it's striking you So you could find out about what's causing it? What helps with the pain? What kind of brain state you're in when you have that kind of pain But the pain itself something like Russell's claim is very intuitive. Yeah, that's all I just say It's very intuitive. I'm when you ask your former question. Yes, but how do you know that that's all there is? Yeah, um There is a legitimate question, but it doesn't take away How intuitive the claim is how compelling the claim is that I know perfectly well What a headache is that you'd try and tell me right? If I go to twin earth and the doctors there say well, I know it feels like a headache But actually we've looked to be done the brain scan. That's not really a headache. That's not what you'd call a headache It feels like one, but it's not really a headache There can't be a ringer for a headache a ringer for a headache is just a headache. You see what I mean? Yeah, so that seems very compelling the question how we know it's Is right is an interesting one, but it's not being addressed here. You see what I mean So Russell's idea is When you come to color it's just like headache when you know what the redness of the red thing consists in when you've seen The redness, you know all there is to know about that qualitative character You couldn't go to twin earth and be told these are ringers for red things That's his intuition. Yeah. Now. I agree that there is a legitimate question. How does he know and so on but? To get the compelling what he's saying seems you don't have to go into that kind of meta theoretical kind of thing, yeah, I Realize you might feel that's evading the question, but I That's not the question you're raising is not at the level at which these guys are arguing. This is here. I mean, yeah Yeah, good if you're a bit confused that shows your understanding He is who? Yeah, just carving off the sensation You're carving off the sensation. Yeah, is there really a dispute here? Isn't Russell really talking about the sensation whereas Locke is talking about the characteristic of the objects That's your point. Yeah, um, I think that's a perfectly natural way to think of it And I actually I want to come on to this now. So as with your question Let me speak a little bit further about that and then come back Okay, because there's a piece I want to get in place before we So So the question is that you guys are raising is should we think of balloon is The qualitative characteristic as something that has to do with the world out there or is it something to do with my sensations right, that's the issue and When you think in terms of this diagram, the question is take these qualities of characteristics That's the interesting thing right the qualitative character. This is Philosophically fairly straightforward. What the physical characteristics are but what is this qualitative stuff? That's what we want to know about. Is that a characteristic of the object or is it a characteristic of sensation? Yeah, and and on the face Excuse me. It seems like Locke and Russell are agreeing that qualitative stuff is a characteristic of the sensation And it can't be just the same thing as the physical structure The blueness has got that kind of simplicity and unity that the physical structure is pretty complex I mean, that's a very simple representation of the physical structure, but any Unitary color like blue or green or red Seems to have a kind of unity that the physical structure doesn't have It's got a kind of simplicity that the physical structure doesn't have and you could certainly imagine blueness without that that qualitative characteristic without any particular physical structure and Your knowledge of what the qualitative characteristic is seems to be more certain than your knowledge of any physical structure So it seems to kind of lift off from the physical structure It doesn't seem to be just reducible to the physical structure So even if you say well I would go to have a causal theory of what the word blue stands for then still there's a sense in which you're going to have to treat Blueness as a characteristic of sensation and that's the point that you are making Yeah, that the blueness of the blue thing for Locke and Russell both is going to be there as a characteristic of sensation now actually I'm just going to blast on a little bit and Then I really will pause to Let you come back and the inverted spectrum the inverted spectrum How do we feel about the inverse of spectrum do do we all know about the inverse of spectrum the idea that okay? You're looking at the fruit and vegetables in a bowl, and that's the color sensations you get is consistent With my behaving in just the same way as you but when I look at the ball I get the same sensations as you get when you look at this scene So maybe I don't get the same color sensations as you but my color sensations might be Structured in pretty much the way your color sensations are your color space might be mappable onto my color space Yeah, so I can make all the same discriminations as you I associate the same words with each of the fruits as you do I say yeah, yeah, that one's yellow and so on Or rather I say that one's yellow even though I'm getting the sensation you get when you look at this one You see what I mean, yeah So the problem of the inverted spectrum so far as I know was first stated by Locke in Connection with violets. Oh, yeah, that's on violets Now do you understand? Anyway Locke said if the idea That a violet produced in one man's mind by his eyes were the same that a marigold produced in another man's And he means in terms of color Yeah, so Let's see Kind of give you there you go So there you go When you look at this when you look at that scene you are getting the colors that I get when I look at this scene Yes You see what I mean Okay So if the idea that a violet produced in one man's mind by his eyes were the same They're a marigold produced in another man's and vice versa Vice versa So when you look at this scene you're getting what I get when I look at this scene Pretty on the health of looking marigold, but there you go Okay Because one man's mind could not pass into another man's body to perceive what appearances were produced by those organs Neither the ideas hereby nor the names would be at all confounded or any falsehood in either So you can't get inside my head and really know that I'm getting all that weird stuff But it just doesn't matter because what's going on here is that? All the things that have the texture of a violet are producing constantly the idea Which I call blue And all those which are the texture of a marigold producing constantly the idea which I is constantly called yellow So I gave this the same names to the same objects as you do because after all that's going on here Is it's the same texture out there that is producing your idea as my idea? It's producing a different idea in you than it does in me But it doesn't matter because we can use our ideas as signs for one in the same texture So the two of us are able as regularly to distinguish things for our use by those appearances Understand and signify those distinctions made by the names blue and yellow as if the appearances our ideas and our minds Were exactly the same Yeah, so there's no confusion here even though the ideas are So different but no so it might be like that as you go around the class That right that that represents the kind of variation that there is in all our sensations as we all look at the scene in the top left So that's a way really of bringing out that On this view your color experience doesn't give you any insight into the nature of the properties of the objects at all because This one in the top left is not privileged It's not that any one kind of sensation is giving you some special insight into what's going on out there all your color sensations are just ways of Having reliable signs of the physical characteristics of the objects outside you Now I think that's a very natural way of thinking and I think that's I think that's a dominant way of thinking Oh, I think it doesn't make any sense at all And I want to this is the piece I say I want to have in place it I think it really doesn't work and The trouble is that suppose I say if I say to you look don't bother about the pin That is causing the pain just focus on the pain itself You could do that if you say don't bother thinking about the brain state that is causing the headache Just focus in the headache itself. You could do that But if I say consider your current color experience consider your current color experience in the screen say and you say well Don't focus on the external object just focus on your visual experience itself Try it now Can you do that don't look at the object focus in the color experience the thing itself? I mean You can cause a certain amount of ice train trying to do that But really the thing is just not possible right it makes no sense if you try to do that You just wind up staring very intently at the furniture You don't wind up looking inside your head G.E. Moore first made this kind of point and he said the way put it was in every sensation There are two distinct terms and it's best here to think of this as visual experience consciousness in respect to which all sensations are like and something else in terms of which one Sensation differs from another that second thing is the object So the picture is there's a generic Relation of consciousness in which you stand now to the yellow thing or now to the violet thing So this relation of consciousness is generic and there are the colors out there in the world that you are experiencing and that Generic relation of consciousness is very difficult to attend to when we attend when we refer to introspection and try to discover what the sensation of blue is you try to do that thing you try and say well Let me not focus on the external physical thing. Let me just focus on the sensation in here Well, the blue is easy enough to distinguish because that's the characteristic of the object out there that you can focus on but the relation of consciousness that the thing that the sensation of blue is Has in common with the sensation of green the mental thing the distinctively mental thing if you try and do that in visual Experience it's very hard to focus on and maybe doesn't even make any sense If you try and focus on your visual experience itself, but not the objects out there That's the thing that you just can't do But all you get is these tables and chairs and their colors and shapes And those are characteristics of the external scene. They're not characteristics of your inner life In general that which makes the sensation of blue a mental fact seems to escape us It seems if I may use a metaphor to be transparent We look through it and we see nothing but the blue So I think that this talk about color sensations which comes so naturally Not just to you guys but to practically everyone in this area. It actually doesn't make any sense because on the one hand the color sensations are supposed to be Things that well, we have really special insight into the Russell was right about the color sensations, right? That's the idea your special insight into the characteristics of your color sensations That's not something to do with the physical world But your visual experience Doesn't give you any insight into your own sensations when you try and attend to your visual experience itself All you attend to are characteristics of the external objects I'm all we really know about all we really know how to talk about our color characteristics of the external objects And then you say well, but the obvious don't have those characteristics So I hypothesize that backstage in your brain There must be some color sensations that are making the thing fuel the way it does But that's just a theoretical postulate That's just a hypothesis as you might hypothesize an electron you postulate these hidden color sensations There are somehow making the whole thing go, but you have no knowledge of them Whatever any more than you have direct knowledge of electrons. They're just postulated to explain what's going on here And that's really incoherent the sensations can't be both something that we have immediate perfect complete knowledge of and mere theoretical postulates that we don't have any insight into Okay, I will try and wrap this up briefly at the start next time and then we'll go into Evans and His short book the causal theory of names. Okay. Thanks. Great questions