 Yn y ffordd, rwy'n credu i gyd ydw i'w meddwl am ymgyrch yn ymgyrch gynhyrch, i gyd o'r byd o gychwyn ffysigol ym mhug o'r byd yn ddigonol. Rwy'n credu i chi'n ddigonol i'r bynnag, ond rydym yn ddigonol o'r byd o'r byd. Yn ddigonol o'r byd, ydych chi'n credu ei rhai i'w ddigonol, y dylai'r ideaeth ymgyrch yn ymgyrch, dylai i'r bydd yn ymgyrch yn ymgyrch gynghigol a'r byd yn ddigonol. because the problems for dualism and physicalism were that mental states can't be shown on either by the look of it to be causally efficacious. Epiphenominalism just says, well, let's accept it. They aren't causely efficacious, they're epiphenominal. And eliminativism says, well, if they're not causely efficacious, then why do we bother with them at all? Let's get rid of them. Let's just say there aren't any mental states. I hope I left you in a perplexed state last night, because if dualism isn't true, physicalism isn't true, epiphenomolism is hard to take, and eliminativism is even more hard to take than where are we, what are we going? So let's start today. So the 20th century in the philosophy of mind was largely devoted to the attempt to demonstrate that mental states are identical, in some sense, whether type type or token token, identical to physical states. None of these was an unqualified success, and some would say it wasn't a success of any kind. So in the final quarter of the 20th century, one philosopher, Hilary Putnam, Hilaire actually, Hilary is a man, came up with a possible explanation for these repeated failures. He put forward a thought experiment that seemed to show that there could be a principled reason for our failures. Now that would be nice actually, because if you've failed every way you've looked, if you could find something that would show why you've failed on all these things, that would actually be quite a satisfactory response to all your failures. What he asked was, could it be that we're looking for the mind in the wrong place? We've been looking for the mind here inside the head, and thinking that if it's inside the head surely it must be the brain, surely mental states must be neural states. Maybe, says Putnam, it simply isn't the case that the mind is inside the head. To understand Putnam's thought experiment, we first got to understand internalism. We've been assuming internalism up to now. Internalism is the view that mental states are states of the sort that are inside us, states that are in here, literally spatially located inside the head. So the mind and all its mental states are intrinsic properties of a person. What do I mean by intrinsic properties? Two different types of properties. There are properties that I would have, even if the rest of you were to completely disappear. If there was a cosmic accident that led to everything going out of existence except me, I would still have those properties. So probably being female is one such property. If nobody else was here, nothing else in the world, but just me, I would still be female. I'd probably also still be five foot six. Various other properties I would still have that would be intrinsic properties of mine. But as you lot are here, I think, I have lots of relational properties as well. So for example, I'm six foot in front of John. I'm also the sister of Judy. I'm also the owner of Edepus, or it might have got that the wrong way round. But do you see how I have relational properties as well as intrinsic properties? Are you with me? So the internalist thinks that the mind and all its mental states are intrinsic properties, or at least determined by intrinsic properties. So if the environment were to be completely other than it actually is, I would still have all the mental states that I actually have, because my mental states are not relational properties of mine, instead, they're intrinsic properties of mine. So Dickhart, for example, was an internalist. He believed that all our beliefs about the external world could be false. He argued for this by arguing that all our beliefs would be the same, even if the world was entirely other than we take it to be. So let's do the Cartesian thought experiment just quickly. He went down three levels of doubt. What he was interested in is could we find certainty? Are any of our beliefs such that they're certain? And he thought, well, how am I going to find out? And what he said was, I'll find out. What I'll do is I'll look at all my beliefs, and if I can find even the slightest case for the slightest doubt, I'll put them on one side as if they're false. He's got reason to think they're true, but he's also got reason to think they're false. He'll treat them as if they're false. Until he's left, I hope, he thought, with something that's absolutely certain. And using this method, he went down three levels of doubt. So he said to himself, well, OK, my senses have sometimes deceived me. Something that I believe to be black in a shop turns out to be blue. You realise that I'm paraphrasing Dickhart. This is not his own. It turns out to be blue, or one of Dickhart's own examples. I think the stick is straight, but I put it in water and I see it's bent. Well, if your senses have deceived you, does that mean you should put all your senses in the doubting basket? So should you treat all your sensory beliefs as if they're false? Because in the past, you've had reason to doubt them. What do you think? OK, lots of people are saying yes. Anyone say no? I've assumed that you believe in something just because of one thing, like you believe in something straight. When you put it in water, you have different additional information, which it looks to the extent, but you know that's because of refraction. Well, we know that. Yes, but you're absolutely right. The fact is, what Dickhart said was, well actually all that does is cast out on those sensory beliefs that I form in conditions of suboptimal conditions. So the only way I know that my sensory beliefs have deceived me is because I've trusted my sensory beliefs. So I see the stick straight, I put it in water, it looks bent, and I think hello. OK, I've now got reason to think the stick is straight and I've got reason to think the stick is bent. Something's got wrong here because it can't be both. So what do I do? I test it with my other sense. I use my sense of touch to see that actually even when the stick looks straight, sorry, looks bent under water, it still feels straight. So I've got more evidence for believing it's straight and that's why we come up with a theory of refraction. Why should this happen? Because like bends when reflected off an object in water is that a reasonable account of refraction. OK, so we've still got only very few beliefs in the doubting basket at the moment and the next level that Dickhart went to was the level of dreaming. OK, you all think that you're in a lecture theatre with a philosopher in front of you lecturing. Do you think it's possible that you could wake up in a second and find yourself still in bed? You don't agree with each other. OK, those of you who said no, why not? You said no and you said no. It's not the sort of dream I have. I bet you have that tonight. I bet you have that dream tonight. I won't ask you what sort of dreams you do have. Because I have input from other people which I wouldn't have in my dreams. Oh, wouldn't you? No, not in a... I mean, all my dreams would be into one towards one thing. It wouldn't... Have you never had a lucid's dream? A dream where it really seems to you as if you were awake and then you're completely amazed to wake up? I never had an argument in my dream. So far, yeah. OK, well, maybe treat you as unusual for the purposes of this experiment. And I bet you will have an argument in your sleep tonight. We can only distinguish there are such things as dreams because we actually have a lot of evidence of the difference between dream and non-dreaming and it's a bit like a stick case. OK, I hadn't got that far, but Frank's giving the answer. What I was going to go on to ask is, OK, given the phenomenon of lucid dreams, the fact that sometimes when we're asleep and dreaming, we believe that we're awake, I put to you that it could be with you at the moment that you believe you're awake, but you might wake up in a minute and find that you were dreaming it all. In which case it's not, as you believe it is, true that there's a philosopher in front of you. It is with you as if there's a philosopher in front of you. So it's true of you that you believe there's a philosopher in front of you, but there isn't a philosopher in front of you. I don't know what you have in your bedroom, but there's only one philosopher in my bedroom. OK, so the fact is you can have all the reasons you think you have for believing that the beliefs you have are true and yet they might still be false. So the dreaming argument puts on one side all the beliefs, puts on one side as if they're false, that is, all the beliefs that would be false if you were dreaming. Now that still leaves you with beliefs like 2 plus 2 equals 4, which is true whether you dream it or whether you're awake. So any belief that would still be true whether you were awake or asleep isn't yet in the doubting basket. Are you with me? OK, so now we go to the third level of doubt, which is the level of the evil demon. Now that'll get the hackles up of people who don't believe in evil demons, but actually the evil demon is unnecessary because what Descartes is asking you to consider here is two of your absolutely fundamental beliefs. You believe that your perceptions are caused by something outside yourself, and you believe that your perceptions are a good guide to whatever it is that's causing them. Those are two beliefs you have. Now the trouble is you can't get outside your perceptions to see what is causing them, can you? And if you remember, we looked at whether A causes B. You have to be here, don't you, to see that A, you have evidence for the belief that A causes B because you have to see a correlation between the two. And if that's a perception, and that's the cause of your perception, you can never be in that position. You always in that position. The world that you perceive is actually cut off, you might think, by your perception of it. It could be with you exactly as you believe it to be, so all your beliefs are exactly as you take them to be, and yet the world is completely other. And Descartes said, so the belief that your perceptions have external causes, you have no reason to believe that because you can't get outside your perceptions to see whether your beliefs have external causes. And also that your perceptions are a good guide to the nature of the causes. Well, how do you know that? You don't even know your beliefs have causes. So what Descartes actually think is there might be nothing outside. The only thing that could exist as far as you know is that your mind exists and that it is with you as if things are thus and so. You don't know that they are thus and so. And so Descartes thinks that that's an impossible thought experiment. He thinks we simply cannot imagine that there's nothing outside, that there is only our own mind. And so what he does is he puts in an evil demon. We would maybe put in an evil scientist or something like that. I don't think that is as good as the evil demon because the thing about the evil demon is it's supernatural. The demon could be causing you to have all the beliefs you're having without there being anything that makes your beliefs true. Do you see what I mean? So you believe you're sitting in a lecture theatre listening to a philosopher with a light shining on her in a PowerPoint presentation which has got some lovely pictures coming up later. And so on. You think that, but none of it's true, is actually there's just your mind. There isn't even your body. Your belief you've got hands. The demon can come in between you and that belief. Do you see? We've reached hyperbolical doubt. And that's at the point at which Descartes says, okay, here I am, the only thing of which I'm certain is my beliefs about my own beliefs. How interesting because I thought that it was the world of which I was most certain. It turns out to be my beliefs about the world of which I'm more certain. And at that point he starts thinking, well, what do I know then? Let's have a look at these beliefs. Let's look closely at what a belief is and why I... And he decides, actually there is something of which I'm certain. And does anyone know what it was? Cogito ergo sum. Therefore I am. There are thoughts. Therefore, well, we won't go into whether it's inference or performance. But because there's thinking, he thinks, if I think, I must exist. And that's the cogito. Anyway, do you see that Descartes on that ground must be an internalist? Because if he's assuming that his thoughts would be as they are, even though the world is completely other than we take it to be, in other words, all our beliefs about the external world might be false. Descartes must be thinking that the identity of our beliefs themselves are functions of our intrinsic states, not of our relations to the world. So, here's a pretty picture. I'm rather proud of this. Okay. So, internalism, the world we think we're in, okay, world one, in which our thoughts about the external world are mainly true. I mean, we know they're not all true, but they're mainly true. So, if we have beliefs about cars and trees, it's because there are cars and trees about which we have beliefs. Okay, so the world about which we have beliefs and the beliefs we have about that world are appropriately related. So, our beliefs are true. This is world two, which Descartes is considering. I couldn't find a demon on PowerPoint, but I found an evil scientist. So, world two, we have exactly the same thoughts about the external world. We believe there are cars and trees and lecturers and philosophers and things like that. But as a matter of fact, all there is is an evil scientist who is causing you to have these thoughts. So, the cause of your perceptions and thoughts, et cetera, is entirely other than you take it to be. But notice the identity of your thoughts is a function of you. It's got nothing to do with the world. Are you with me? So, that's an internalist belief. Penny. But what if you discuss your thoughts about the world with somebody else and they have exactly the same? Everybody you talk to believes there are trees and cars. Well, they do, don't they? If you ask Susie whether there are trees and cars, she'll probably say yes. Well, let's go back. Do you remember yesterday I made a distinction between the world's thoughts and language? So, what you're wanting to do is to check your beliefs about the world against Susie's beliefs. Now, tell me, what makes you think that your beliefs about Susie are not beliefs about the external world? They are. And why couldn't the demon come in between your beliefs about Susie in exactly the same ways it would come in between your beliefs about the car? It would. So, you believe that you say to Susie, you believe that Susie's there for a start, and you believe you say to them, oi, are there any trees? And you then believe that she says yes. Okay, so your beliefs are all nicely consistent and you think, ah, lo, there are trees, because Susie says there are. But you're actually just jumping on the spot, aren't you? You're not going anywhere, because it's no good. It's a bit like me checking the times against the telegraph. Except, of course, the times doesn't exist. Why should there be a demon? What's the point? The point is not... The demon is actually not the point at all. The demon is only brought in because Descartes can't imagine that there's nothing. The fact is that you have beliefs, which is that your perceptions of beliefs are caused by an external world, and that your perceptions are a good guide to the external world, and you have absolutely no justification for that belief. Do you see? But that's what Descartes is getting at, because what he's asking is, what is knowledge? And you can't have knowledge unless you have true beliefs. We claim to have knowledge of the external world. Our beliefs about the external world will only count as knowledge if they're true. What justifies us in thinking they're true? Actually, says Descartes, nothing. And yet we can't not believe them. Descartes isn't claiming we don't have these beliefs. We definitely have these beliefs. What he's questioning is to what extent they're justified, or to what extent they count as knowledge. I saw another couple of... Patrick and then Chris. Do you mean logically they're justified? There's no other sort of justification than logically. Hang on, empirical justification. Why do I believe this table is there? I can see it, I can feel it. All of that's empirical justification. But actually, my belief that the table is there is justified by the fact that my belief that I can hear it, my belief that I can see it, both logically support my belief that the table is there. The demon can get in between all these beliefs. So empirical beliefs are as much in need of logical justification that is put in question by the demon as any other sort of belief. The only reason you can ever have for believing a belief is true is that there is another belief that supports it. Beliefs are, if you like, a self-contained system. Chris. If you believe in an evil demon, you're at a dead end, in fact, because that explains everything, and we might as well go home now. Well, but it isn't like that, is it? The evil demon is put in there just as a device to make it easier for us to undergo this thought experiment. It's certainly true that if you decide, okay, there is an evil demon, then we might as well go home. But you've got no more reason for believing there is an evil demon than you have for believing there's an external world. And so what we're doing is, as always, this is what philosophy does, is it takes your belief and it says, well, what's your justification for it? Let's pull it apart a bit and let's see if you are justified in believing it. And the thing is, you've got this lovely little faith. Interesting word, that, isn't it? In the external world. And actually what Descartes is showing is that it is faith because you have got no good reason for believing it even though we do all believe it. Let's move on. Do you like my pictures? I was really proud of those. Okay, so if you remember, we're looking at this because Hilary Putnam wants to argue that maybe beliefs aren't the sort of states that get inside us, that are inside us. So that's internalism, which you were all assuming, weren't you? You were very happy to go along with Descartes' thought experiment. You can see why Descartes thinks that it's possible that all our beliefs about the external world are false. Now Putnam's coming along and he's asking us to question internalism. He's asking us to think about the possibility that beliefs are not states that depend on our intrinsic properties. Okay, well he asks us to imagine our planet Earth, well that's easy. A person, Oscar, which we can model on Bob Stone just to make life easier. Another planet, Twin Earth, and Oscar's doppelganger, Oscar Twin Earth. So, Tosca or something. So this is what we're imagining. Twin Earth is exactly like Earth, except that the stuff that runs in rivers that they drink and shower in, et cetera, has to come in chemical composition X, Y, Z instead of H2O. Look, the two came out as a subscript this time. Okay, we'll call this water Twin Earth. Incidentally, when Putnam did this thought experiment, he obviously didn't take into account that we are mostly water. And just ignore that. It's a complication that haunts this experiment and it's really quite irritating because it's completely irrelevant. But just to say, it's not gone unnoticed. Causing us to, yes. Oscar on Twin Earth is identical to Oscar on our Earth with respect to all his physical properties, his neural properties, et cetera, his phenomenological properties. So the world seems to Twin Oscar exactly as it seems to Oscar. Okay, so the phenomenal properties that Oscar has are exactly the same phenomenal properties. So if Oscar sees Susie's red waistcoat, it is this morning, then Twin Oscar also sees Twin Susie's waistcoat. Has the same experiences and so on. So physical properties are identical, phenomenological properties are identical, and therefore their behavioural dispositions are identical. In other words, what we're saying is that Oscar and Twin Oscar are qualitatively identical with respect to their intrinsic properties. Okay, this is the thought experiment. Penny doesn't think this is possible and we all know that it's not empirically possible, but the question is, is it logically possible? Of course it is. Because he can't have the same physical properties, he has to depend on water for life, and water doesn't exist on H2O for life. Why couldn't he depend on XYZ for life? Because he wouldn't have the same physical property. Okay, this is why water was bad, but I hope the rest of you see that this is irrelevant. It really is irrelevant. Never mind, it is irrelevant. If you think it through for yourself, you will see that it's irrelevant. Never mind, let's move on. Okay, ah, more pictures. Okay, so this is Twin Earth, and you've got Twin Oscar here, whose eyes have gone green, I see, and you've got a glass of XYZ here, and Twin Oscar is thinking to himself, that's water. And then down on Earth you've got Oscar himself, and you've got a glass of H2O, and Oscar is thinking to himself that's water. Okay, so far so qualitatively identical. The next thing we have to imagine is that Oscar is overnight transported to Twin Earth, where he finds himself in the same room as his doppelganger, and both of them are looking at a glass of water, the same glass of water. But this is of course XYZ, because we're on Twin Earth, and both of them are thinking of that same glass, that's water. And the question we're going to ask is, are the twins thinking the same thought? So here they are. We're on Twin Earth, both of us are on Twin Earth, and there's one glass of XYZ, looks exactly like water, but actually is XYZ, not H2O. And both Oscar and Twin Oscar, who haven't noticed each other, or they'd be freaked out, are thinking that's water. Are thinking that's water. And the question we want to ask is, are the twins thoughts the same? Are they thinking the same thought or not? Think about it, and put up your hand if you think they are thinking the same thought. In one respect. Well, it's the same concept. So they're literally taking the same thought. Just put your hands up will you? I'm not saying what thought they have, I'm not saying anything about it. I'm asking for your intuitions, is the thought that they're having the same or not? Okay, most of you think that it is. The rest of you, do you actually think not, or are you sitting on the fence? Put up your hand if you think they don't have the same thought. And you don't know this thought experiment of old. I'm not saying what thought they have, I'm not saying anything about it. I'm asking for your intuitions, is the thought that they're having the same or not? Is the thought of old. David, put your hand down. John, do you think they don't have the same thought? Why not? Because they're thinking about different things. Okay, well they're both thinking about this, aren't they? No, they're both thinking about this. But it is the same thing. They're in the same room, and they're both thinking this of that. So the subject of their thought is exactly the same. It's the same glass of water. Is that one of them's wrong and one of them's right? Who said that? Who said one of them's wrong and one of them's right? Well done. But you know about this as well. Right, okay, let's move on. If you're an internalist, you have to say that the twins are thinking the same thought. So actually, given that most of you are internalists, we've already agreed that, at least consistent, if you're an internalist, they have to be thinking the same thought. Because if Oscar and Twin Oscar are physically identical, neurophysically identical, they're also behaviourally identical and phenomenologically identical, and beliefs superveen on intrinsic properties, as their intrinsic properties are identical, they must be thinking the same thought. So your internalist's intuitions caused you to say that they are thinking the same thought. Okay, fine. So, as a... Okay, that's what I've just said. But we might want to insist that the twins' thoughts are different. There should be an S on thought. A different. And one reason for thinking this is that Oscar's thought is false. And yet Twin Oscar's thought is true. I think that's what you were getting at. That's actually... Okay, that's what you said. I'm pretty sure you were getting at, John. When Oscar is thinking about water, so when he thinks that's water, he's thinking about H2O. But the liquid he's thinking about on twin earth is not H2O, it's XYZ. So his thought that's water is a thought about something that's not... Sorry, his thought that's water on twin earth is a thought about something that isn't water and is therefore false. Are you with me? So let's go back to this. For Oscar, his concept of water is a concept in the extension of which is H2O, not XYZ. For Twin Oscar, his concept water is indeed a concept of XYZ. So when he thinks that's water, his thought is true. But when he thinks that's water, his thought is false. That's the thought. I'll come to you in a minute. There are a couple of questions there, but let's just finish the thought experiment and then we can look. So when Twin Oscar thinks that's water, he is thinking about twin water and twin water is XYZ. And when both the twins are on twin earth, Twin Oscar's thought that's water is about something that is twin water and it's therefore true. So Oscar's thought is false. Twin Oscar's thought is true. And if their thoughts were the same thoughts entertained in the same circumstances, then their thoughts would have to have the same truth value. Why do I say this? Because it's the content of a thought relative to a specific context that determines its truth value. So for example, the content of the thought it's a cat entertained whilst looking at a dog is going to generate the truth value false, isn't it? Are you with me? So if we go back here, there's a difference between the truth conditions of a thought. This is a very important logical point. The truth conditions are a thought determine its content or are its content, if you like. So with Oscar, his thought that's water is true. The conditions under which it would be true is true but would be true when H2O is around. So the truth conditions plus context determine truth value. So there's a difference between truth condition which in effect is meaning and truth value, so the meaning of a sentence in a context determines its truth value. That's why we might think that Oscar's thought oops, I've lost it. Here we are. So the truth conditions of Twin Oscars water concept are XYZ. The truth conditions of Oscar's water concept are H2O. Different truth conditions, we know that because in the same context they determine a different truth value. I see that there are questions so I'll come back. I want to get the experiment out and then come back to the questions. So if the twins, if the twins thoughts differ in truth value it can only be because their contexts differ and we know that that's not the case in this thought experiment or because the contents of their thoughts differ. Ex-hypotheside they're embedded in the same context when they're both on twin earth must be the contents of their thoughts that differ and this means they're not thinking the same thoughts. So Putnam argues that as the things he believes the twins thoughts do differ in content but as they're identical with respect to their intrinsic properties in other words all their internal properties their intrinsic properties are the same this has to mean that thoughts the very content of your thought is a function of your relations to the environment not of what's going on inside your head. So the very nature of your thought is determined by the environment not by things inside your head. Internalism therefore says Putnam is false and externalism is true. Okay let's take a few questions before we go on. You've had your hand up for ages going You said if the thoughts were the same the definition of the twin earth Oscar is that water is xyz so I think their thought was the same because they had different definitions I'm not disagreeing with externalism. Hang on what do you mean they had different definitions. The definition of Oscar in twin earth was the different definitions. No both of them have no idea about the molecular content of water. In fact we can imagine that this takes place before 1759. Okay I can imagine now I travel back to the bridge where I am where my mother lives I don't understand in the morning I'm too tired I open the fridge because I need a glass of water I drink it it's not water it's Uso and it's not my belief is not true it is external the conditions are different usually I... No I'm sorry you're confusing truth conditions and truth value. Again look the content ooh it's all green can you read it? The content of a thought which we might think of as the conditions under which thought would be true or false Okay so to grasp a thought is to grasp the conditions under which that thought would be true and the conditions under which it would be false Do you accept that? So if I'm trying to teach a child the concept cat I'll show it lots of cats black ones, furry ones, thin ones et cetera et cetera lots of different cats and I say that's a cat, that's a cat, that's a cat and when I think the child's got it I point to a dog and I say is that a cat and the child should go no that's not a pussy cat now when she says that I know that she's grasped the truth conditions or at least I have evidence that she's grasped the truth conditions because she knows when it's true that the thing I'm pointing to is a cat and she knows when it's false that the thing I'm pointing to is a cat so she's grasped the meaning of cat so the content of a thought is determined by the conditions under which it's true or false to grasp a thought, to understand a thought is to grasp the conditions of truth and falsehood and the content plus context so if you have the content that's a cat those truth conditions that we've just talked about and the context is one in which there's a dog those two together determine truth value false but if the context is one in which there's a cat they determine the truth value true so when you go to the fridge in the morning the truth conditions of your thought that's water are nothing to do with uzo are they uzo would generate false so if you have those conditions are unless it tastes like water it's not water and so if you have uzo how do you spell uzo it's false whereas if it had been water it would be true thinking of the child recognising the cats say on the 20th occasion sorry can I interrupt you a second does anyone mind if I open the door because I'm going to faint in a pool of little I'm hot sorry go on it seems to me that it's quite interesting because you show a picture of a cat and another one and another one or I show real cats yes and then on the say the 20th time you show something that's in every respect similar to all the other cats that you've shown when you say is it a cat or not well it looks like a cat it purrs like a cat but actually it's a robot it happens to be a robot that actually looks okay well let's run through this shall we and I think the child was right to say it was a cat oh does anyone else think the child was right to say the robot is a cat really and the child oh I'm sorry it was certainly right in that it was justified to say it was a cat was it true what the child said hang on let's make a distinction between justified and true nobody is denying that the cat would be the child would be justified in saying this is a cat I'd probably say it was a cat if it's really phenomenologically indistinguishable from a cat until you cut it in half which of course you would never do there's a difference between being justified in saying it's a cat and actually the child demonstrates its grasp of cat by saying it's a cat under those circumstances it's still not true and in exactly the same way Oscar is justified I don't think there's any problem with saying that he's justified in thinking that's water what we're asking is not whether he's justified but whether it's true I think it is true okay but you also think that it's true of the robot cat that it's a cat and I don't think many people would agree with that would they? okay it's only if you can stand right outside that situation if you are but in order to determine truth that's what you've got to do epistemology and metaphysics are completely different epistemology is to do with what we know what we're justified in claiming and metaphysics is to do with truth what is actually the case and the point of a thought experiment is to pull apart what we might be justified in saying and what we might be true in saying and why it would be true rather than merely justified but surely with anything scientific hasn't Popper effectively shown that you can't grasp absolute truth in that sense? we're not doing science here we're doing philosophy and the thing about philosophy is that it's not constrained by the laws of nature it's constrained by the laws of logic it's a thought experiment it's a thought experiment which is governed by the laws of logic not by the laws of nature even if it's true that if we were in that situation if we were Oscar there's no way it's a bit suspicious that we've found ourselves in a room with a doppelganger etc but there's no way we would know that that isn't water but it still isn't water is it? we know because we're standing outside and that's what it is to do the thought experiment that says that's water that's a different question we could say I'm rather assuming Oscar the truth conditions not the truth value the truth condition of Oscar's water concept equals it's true when applied to H2O and false otherwise now Putnam is definitely assuming that and we might think it's a reasonable assumption because Oscar has grown up in an H2O world etc we know that science has shown that water is H2O therefore water is necessarily H2O that's why Putnam thinks that but what you're suggesting is that maybe the truth conditions of Oscar's water concept are true when applied to H2O or XYZ I'm saying it applies to Oscar it doesn't apply to anything to do with H2O or XYZ exactly the same way as all the other equations and it does the things which he expected water to do and what does it mean? that's a different theory about the same thing what we're arguing about here is this question excuse me the question is what are the truth and falsity conditions of Oscar's water thought or in other words what is the meaning of Oscar's water concept or his water word okay one possibility and this is the one Putnam argues for he doesn't just assume but I rather assumed it in this is that water means H2O I've just suggested that maybe water means H2O or XYZ and Bill's suggesting I think that water and I think I'm sorry I don't know your name Harold okay water means anything satisfying the phenomenological and dispositional properties of the stuff that on earth is H2O no I'm saying that the stuff that is on earth is XYZ in other words this is the same as the cat that is in fact a robot but is indistinguishable from the cat no you may have a different one but I'm asking whether this is what's wrong with that Oscar thinks of its properties sorry this is us trying to work out what the content of Oscar's thought is it's not what Oscar thinks he has a water thought I know you are on this one Oscar's thought on twin earth would be false and on this one and this one Oscar's thought on twin earth would be true are you with me? I just don't like the reference to H2O because it's no past Oscar's thought it's the thing that by drinking it satisfies me I see it runs in rivers and it comes out of the sky that's what he's thinking soon because I know that there's water it's that bloody fact if he drags XYZ it would not satisfy his thirst no it would no you're thinking because if it's not XYZ so why shouldn't XYZ? it wouldn't taste the same this is actually irrelevant this is a thought experiment please not an empirical experiment we know that something that has a different molecular structure on earth would have different properties we're doing a thought experiment so we're looking at logical possibility not empirical possibility we know it's not empirically possible but it is logically possible there is no logical reason for example couldn't it have been the case that as a matter of fact the only testing on water has been done sorry there has never been anyone testing the molecular structure of water in Russia for some reason it's a bad example out of Mongolia and somebody a bored graduate student one day thinks I'm just going to go I've got nothing to do haha I'm going to test the molecular structure of this water here and he tests it low it's XYZ well that's odd he thinks he tastes it and he looks at it and then other people go out and it turns out that in outer Mongolia for some reason the stuff that comes out of showers and in rakes and they drink and so on is all XYZ now at that point you might start thinking well that's interesting water isn't H2O it's either H2O or XYZ now if you think that that's possible you might think that what we're discovering here is that both Oscar, Twin Oscar and Oscar have water concepts that say H2O or XYZ in which case the truth values are the same are you with me and if we go back to Harold's idea of and I believe that it's because I think Bill is getting worried about the fact that I put H2O in here unnecessarily sorry he is worrying unnecessarily not I have put it in unnecessarily is that as long as you've got something that actually satisfies all the operational definition of water in other words it looks like water does the things that water does slakes your thirst etc then it is water if it looks like a duck it quacks like a duck there was are the twins thinking the same thought is the question about whether their thoughts are both valid are true? No, no, no you see that's another question that forgive me Susie manifests the failure to grasp the distinction between truth conditions and truth value and Susie is very far for the only person in this room who is failing to make that distinction what we are asking is not are the twins thoughts both true or false we are asking are the twins thinking the same thought what we are looking at here is the individuation conditions of thoughts what makes one thought the same thought as another thought so if you imagine you don't have the concept chair unless you can look at this chair and say ok that's one chair and there's another and there's another so one chair ends here and starts here and one chair ends here and starts here if you've got the concept chair you can individuate chairs you know how many chairs there are you know when one chair starts and one chair finishes and what we are doing now is looking at our concept of belief and in particular belief content and we are saying ok what makes it true that this belief has this content and this belief has this content too ok do we think that Oscar and Twin Oscar have the same thought in other words two tokens of the same type or do they have different thoughts so two tokens of two different types and the reason it isn't looking at the truth of their thoughts is that we are looking at if you remember I made a distinction between truth conditions and truth value so that's to do with truth conditions and the truth conditions plus a content determine truth value so I'm taking the belief if it's a reasonable belief that their beliefs are different truth values I'm taking it back to say as they're in the same context they must have different contents I could see I was losing you in that bit I was running out of steam because I could see that you were going there Chris It seems to me if we want to indulge in a thought experiment we have to accept the rules of that thought experiment and not challenge the rules because you don't get the result of the thought experiment out clearly the rule of this is that H2O and XYZ are different now people seem to be arguing they're the same I completely accept and you're absolutely right that in order to understand the thought experiment you have to accept the rules of the thought experiment if the thought experiment turns out not the way you think it should you can go back just as you can in the laboratory and say well that's interesting my theory generates this observable condition but that observation wasn't born out I now see that that observation is false was it my theory that's wrong or the initial conditions that I tested the theory in or the auxiliary assumptions you're confusing a thought experiment with a real experiment the thought experiment and the real experiment are structurally exactly the same the only difference between the two is that one is governed by the laws of nature and the other is governed by the laws of logic isn't that where this law goes wrong because in fact right from the beginning you call two different substances by the same name and that's an linguistic error oh is it? tell me what this means back two different things that are denated by the same word and of course it could be a verb as well but in this particular experiment where you're depending very much on what water means and the fact that it's applied to two different things it's an absolutely illogical thing to do no because the whole thought experiment depends on this so here I've got a series of squiggles we impose meaning on it but it's ambiguous there are lots of different meanings we could put on it so we know that meaning is not a matter of the shape of the squiggles we make on paper nor is it any matter of the sounds I make when I say bank there's more to meaning than that so because I'm using the same squiggle to identify the thoughts of Oscar and Twin Oscar doesn't mean they mean the same thing and what we're trying to do in this thought experiment is say do they mean the same thing that's what we're asking so the fact that it's the same squiggle is very important because we don't want to confuse the experiment with using different squiggles which will immediately get you thinking they're different things and they might not be because you're saying that water for one twin means H2O and water for the other twins well that's what Putnam's saying so actually the experiment will only work by defining water in that way yep you're absolutely right which is why the question that I asked in response to so what we're asking is what is the meaning if you like or what are the conditions of truth and falsity of Oscar's water thought and this is what Putnam believes he thinks that water means H2O for Oscar and this is two other possibilities that have come up this is the one that I wrongly thought that Bill meant but actually lots of people would say that if water means H2O or XYZ then both their thoughts are true aren't they because if the truth conditions are the same it's either H2O or XYZ then in the same context this is XYZ so it does satisfy both Oscar and Twin Oscars concept so the thought experiment can't work if that's the meaning of water and if this is the meaning of water the experiment can't work again because if water means satisfies the operational definition of water in other words looks like water feels like water tastes like water is indistinguishable phenomenologically behaviourally etc from water if that's what water means then again if XYZ is all those things and by X hypothesis it is then these two thoughts have the same content and in the same context they determine the same truth value so Putnam's thought experiment does not work if water means either of those things so the question to ask is do we think that water means that or that or that what water means to Oscar though Oscar's belief about what he means are different from what Oscar means I'm sorry let me let's do that little thing that we did again now who can I pick this time Colin Colin believes Marianne is wearing purple is that true Susie went ok you got one sentence embedded in another sentence ok now that's he's just said that's true and I take it you believe that's true as well but could they both be false could that be true and that be false once again we've got the truth conditions of that that vary completely independently of the truth conditions of the embedding sentence now let's look at Oscar believes that is water Oscar believes that Oscar believes that that is water you with me ok do you see that that's one sentence and that's another sentence ok could that be true and that be false etc yes it could because actually you have to ask that in the context of a belief I mean he might believe that he believes it's water that doesn't mean that he does believe we're asking if I'm asking you about our water concept ok does water sorry is it true that is water is that true if and only if it's XYZ or is it true if and only if it's either XYZ or H2O which do you think our water concept is now interestingly you all believe that you believe that in that glass there's water but I'm just pointing out to you that you have no idea what this belief that you believe you have is that's why we're having such trouble here are you with me you all believe don't you that there's water in that glass not Uzo it might be vodka it's water ok now you believe that therefore that's H2O but what I'm asking is why don't you think that you believe that it's H2O or XYZ what I'm showing you is maybe you should think of it as H2O or XYZ do you see sorry the whole thing is circular this thought experiment has been keeping philosophers going for a long time and you have just solved it right there and then Patrick I think if you reduce this argument to an if then argument ok so if you near your arguments then yeah but in a sense that's simplified so putnam putnam like most of us say putnam has as his premise he privileges water as H2O so if he privileges water as H2O then I agree with him actually in the argument but I think it's worth pointing out that is an assumption but that's what I've been pointing out for the last 10 minutes it is putnam is assuming that water means you know what I mean and what I put to you is that actually you believe this too you don't believe that your water concept that is water is true if it's either H2O or XYZ although I did put to you with my out of Mongolia thank you thought experiment is that actually maybe you should think it's H2O or XYZ and when Harold came up with his cat example I put it to you that actually whether we could know it or not if this cat that is indistinguishable sorry if this animal this thing it's not even an animal that is indistinguishable from a cat is actually a robot even if we couldn't know for sure or even know at all that it isn't a cat it still isn't a cat that's a metaphysical truth whatever the epistemological truth of what we could or couldn't know because the fact is that cats are animals they're not robots well let me think about that for a minute question of the rigid designators that we were looking at yesterday that H2O is a rigid designator why don't you make sure we're a bit too iffy about well done very well done actually it looks as if both water and H2O are rigid designators if Putnam is right we're thinking that both of them are rigid designators but what you are doing here is questioning whether that's true so yes well done that's nicely put rigid designation is a very useful concept because it enables us to track things through possible worlds but of course we can question whether our intuitions about possible worlds are true or not and that's what we're doing in asking about these possibilities David with this what you're really saying is that H2O introducing these terms is just a sort of pseudo scientific gloss but it's nothing scientific about it at all not in the slightest, no Putnam would say that water means H2O to us because science has shown that water is H2O but if it's pure water it would rule out sea water which is a lot more than H2O to rule out other things and even if it's pure water then the essence of water is that it's ionised that's what we're doing here to determine the truth but it's making it a scientific and then you're saying it's nothing to do with science it's philosophy well then don't introduce these scientific terms because you can't do it ok let's have a look at this a question Truth value of that is water ok so I say that we've got to do two things one is determine the meaning of that is water and the second is to determine whether meaning is satisfied in a context ok if I say if I utter to you a sentence in Russian ok I'm hoping that none of you speak Russian and actually I can't utter a sentence in Russian anyway but if I did and then I said to you is it true what would you say to me you've no idea why don't you know you're not talking scientifically here you're talking about meaning what's that got to do with the truth value of anything do you see what I mean we usually forget that you have to know the meaning of an observation statement before you can then test it it's really in the usage of the word that's a philosophical theory that's questioned by many philosophers and what we're questioning is how we use the word water do we use it only of H2O or would we be right to use it of XYZ the fact is that any observation statement in order to be tested there are two things that contribute to this one is entirely the work of philosophers what the meaning is the other is entirely the work of scientists having determined the meaning what is the truth value that's a logical study and you absolutely can't get away from the fact you need both so we assume that science has shown that water is H2O therefore it's necessarily H2O but that's on the assumption that the meaning of water is the stuff around here if you see what I mean the stuff we drink and so on we can ask a question we can say okay are we going to change the meaning of our word water so it's H2O or XYZ or are we going to say that the word water means H2O and that XYZ is therefore not water and that would be a decision science wouldn't have any say in that that would be a decision what we decide to do we look at the history of for example we think of two different sorts of jade but we look at where have we got a situation where we've said actually there is instead of two different sorts of this stuff isn't a whatever at all fools gold is a bad example there but here's something that looks like gold but we're not going to say it is a form of gold as you say it isn't gold at all so decisions about meaning are logical decisions they're decisions for philosophers they're nothing to do with science at all so I'm talking about this not this I'm spinning the possible worlds on this one in order to find out more about this one let's move on because we've got three minutes left okay so Putnam is saying that externalism is true okay here's externalism now do you remember we had this before what's changed something has changed that's right so world one is the externalist world I'm sorry they're both externalist world what we're saying is that the identity of your thoughts isn't determined by your intrinsic properties instead it's determined by the world itself so if the world has cars and trees in it then your beliefs will be beliefs about cars and trees but if the world has evil scientists or evil demons in it then unknown to you are about demons or scientists so on this story the Cartesian thought experiment is actually incoherent if there were an evil demon we wouldn't have thoughts about chairs students, philosophers etc because if they don't exist we couldn't have thoughts about chairs, philosophers etc so externalism is a very different way of individuating content the content is actually determined by the world if you like the world comes right into the mind but the mind also reaches right out to the world the mind isn't located in here at all so if externalism is true mental states have contents that are not inside the head they're not determined by states intrinsic to the subject but rather by the subjects relational states in particular relations to things in the environment that's one argument for externalism here's another this will get your thoughts going as well this is Donald Davidson Davidson imagines that a cosmic ray hits him sorry logical possibility coming up here well I suppose it's an empirical possibility too but the rest of it's logical reduces him to ashes you see I'm a bit uncomfortable about this by coincidence another cosmic ray creates a physical replica of him and nanosecond later or maybe simultaneously that was even more fun simultaneously and the question that we've got to ask is are the thoughts of the swamp man he's in a swamp incidentally when the cosmic ray hits him are the thoughts of the swamp man the same as thoughts of Davidson so here we are that's Davidson and the swamp man is a physical phenomenological and behavioural replica of Davidson exactly the same as Davidson and the question is are his thoughts the same whoops let me ask you that question I hope you didn't have time to read that is the swamp man able to think fondly of Davidson's wife in exactly the same way Davidson does so Davidson has fond thoughts we would hope well he's dead now but he did have fond thoughts of his wife would the swamp man's thoughts would he have thoughts of Davidson's wife would those thoughts be the same as Davidson's he's physically phenomenologically and behaviourally identical today I mean I realise the picture suggests otherwise but as he comes out of the swamp his suit comes together and all the other if you say yes you're an internalist exactly because an internalist believes that the content of your thoughts is a function of your physical, phenomenological and behavioural dispositions if you're an internalist it's interesting he hasn't swamp man hasn't got a wife has he as it was Davidson who sat there at the altar and exchanged the vows with his wife whereas swamp man didn't even exist at that point Harold thought experiment logical possibility we are assuming for the sake of the thought experiment that the cosmic ray has created something that's physically identical I mean sorry you have to go into the logical possibility here you can't those of you who don't accept this thought experiment are fine we'll carry on with the other people who do we've got a whole session of questions afterwards okay you're quite right Patrick if you're an internalist you have to say yes because if thoughts are determined entirely by your intrinsic states then the swamp man must have the same thoughts as Davidson because ex-hypothesis he is identical to Davidson intrinsically is would the swamp man be able to have thoughts about Davidson's children that David himself has bearing in mind that swamp man has never met Davidson's children so it would seem to the swamp man firstly that he is Davidson secondly that the children that he thinks about as his he believes are his but we know they're not because he wasn't their father end of the story now the swamp man believes he does so he believes he remembers that his first swimming trunks were green and that when his mother gave it to him she also threw him in the swimming pool and let him get on with it swamp man believes that because he has all the it is with him exactly as if it is sorry as if he is Davidson but of course actually can you remember P if you didn't experience P usually we would think not it's a necessary condition of remembering P that you have actually experienced P false memory is very badly named I'll come to you in a second okay if you think that swamp man doesn't have the thoughts of Davidson then again you might prefer to reject internalism and take up externalism okay Descartes and Interns but he wouldn't say yes would he he would have to but he would have his soul in there so it isn't just the physical properties the person Descartes was actually much more interested in phenomenological properties than physical properties so if it is with the swamp man exactly as it is with Davidson so everything appears to him exactly as it would appear to Davidson for Descartes that would be enough for it to be the case that his beliefs are the same as Davidson's beliefs and we're much more interested in physical states and also behavioural dispositions so we put that in just to make sure that we've got all the internalists in the same bag okay let's let's move on, I know there are other questions but we've got plenty of time so to embrace externalism is to embrace the idea that mental states are the sort of states we get into rather than the sort of states that get inside us see the difference, I've got a picture here pink externalism are mental states of the sort we get into so your mental state is if you like not just you and what's inside your head but also what's inside your world so the pink down there, your thought about a car you wouldn't have a thought about a car unless cars exist that's externalism, internalism says that your mental states are the states they are just because of your intrinsic properties what's out here is completely irrelevant okay this could be this or it could be thank you the demon or anything or it could be just nothing in fact I shouldn't have put these two in because what I should have put there is nothing so mental states are the sort of states that get into us according to externalism see the pink here and for externalism mental states are the sort of states we get into so I couldn't have a belief about Janet unless Janet existed according to the externalist according to the internalist my thought about Janet is a property of mine quite independently of whether Janet exists or not okay if mental states are the sort of states we get into rather than the sort of states that get into us then all our attempts to construct an account of the relation between the mental and physical states have been based on a false premise we've been assuming that mental states are the sort of states that get inside us we've not been thinking of them as the sort of states we get into which is a whole different ball game identity theory argued that mental states were states of the brain functionalism argued that mental states are states that play a certain sort of functional role and the physicalist functionalist if you remember says that all such functional roles are played by states of the brain and anomalous monism argued that all causally efficacious mental states have physical description and the way we looked at it we implied that all such physical descriptions would be descriptions of brain states so each of the theories we looked at assumed that a mental state is the sort of state that gets inside us not the sort of state that we get into interestingly though and this is where it really does get interesting embracing externalism doesn't mean that functionalism or anomalous monism are necessarily wrong certainly identity theory is wrong but we already knew that anyway both functionalism and anomalous monism can be modified to embrace externalism so the only one of the theories we've examined that can't be modified is identity theory which as I said we knew was wrong anyway functionalism would merely have to widen functional roles to include roles that go beyond the brain and the body and anomalous monism would merely have to widen physical descriptions to include relational descriptions but if externalism is true it seems clear that no matter how much neuroscience can tell us about the brain there's a limit to what it can tell us about the mind obviously it can tell us things about the mind it can tell us which states realise mental states etc but even if the mind is physical on this story those states are not neural states they are not states of the brain references for you and where to go from here but we'll look at that when we come back from the break because we're a bit late so come back at 20 past would you and we'll have the question and answer session