 A oeddwn i ddim yn fynd i fynddau, dyweddyn ni'n gwneud o'r Pwtynum'r ysgrifennuau ar gyfer y rhaid. Ac rwy'n meddwl i'r Efyddon. Fy fyddech chi'n bwysig y Pwtynum wedi'u llyfrnodd o'r disgwysbeth i'r rhaid i'r rhaid i rhaid i'r rhaid i'r rhaid i'r rhaid. is do our psychological states fix the references of our terms and as I said in the very first lecture we had that's the natural way to think about language that it's what's in your mind, it's what's in your head, there is breathing life into the signs of the language is what's in your head that is making the whole thing go, that is making the language, making that system of signs into a representational system in the first place so if that's your head then the question is is what's in your head fixing reference and if you think of it in terms of sense or descriptions or clusters of descriptions then it seems like well the sense or a cluster of descriptions that's something that you grasp with your mind, that's something that you know about so the general question is, just for the people who came in just a second ago, the general question is do our psychological states fix the references of our terms and if what's in your head is a sense or a description fixing the reference, well it looks like that description, that's something you know about, that's something in your mind and that thing there, the intermediary that is fixing the reference of the term, you do grasp that so that's going to be fixing the reference so it looks like on the classic Frega Serral kind of picture the answer to this should be yes, your psychological state is fixing the reference of your term it's a little bit different if you have a causal theory where you do without the sense or description and you just have a causal chain because the causal chain between you and your surroundings that's not itself on the face of it, something interior to your mind the causal chain is something about the relation between your mind and the environment so on a causal chain kind of picture of reference it looks like the answer to this question should be no it is not your psychological state that is fixing the reference of your terms there's a sense in which we're not really in charge of the way our language works rather it's the causal connections between us and the environment that are shaping what we say and think and it's not something that we just lay down there's nothing conventional about the existence of a causal chain there's not a convention of human language that's just the way the thing works is not up to us so that's the kind of framing question in Putnam's discussion is what's interior to your head, is your psychological state, what's fixing the references of your terms and he's got this, let's just think about the characterisation of what a psychological state is and he's got this famous example of Twin Earth that we'll spend most time on today so what's your psychological state, your psychological state is something that's independent of your relations to your surroundings if for anyone who's done Descartes this goes right back to the idea well it might all be a dream it might all be hallucinations, I might just be sitting by the fire thinking I'm giving a lecture I might be fast asleep at home thinking I've made it to the lecture on time you might be as fast asleep at home thinking that you made it to the lecture on time but your internal psychological state could be just the same even if you were a brain in a vat your internal psychological state could be just the same so your surroundings cause you to have different psychological states but what the straights are intrinsically that has to do only with you one way to think of this is in terms of your knowledge of your own psychological states I mean the way Descartes put it, I mean I guess most of you know Descartes I can't cross Descartes meditations I think therefore I am and all that stuff at some point it will pick up well the way he was thinking of it was my knowledge of the physical world that might all be a dream that might not really be happening but I can survey the contents of my own mind I can just look inside my own mind and see there what is going on so you have this domain of your own psychological states over which you really have this special authority and whether or not you are dreaming whether or not there is anything out there you know what is going on in your own mind and that is not just your own mind at the moment and presumably that would apply to your memory of your mental states yesterday and maybe what was going on yesterday was all a dream but you still know what was going on in your mind yesterday if your memory is working then you still know what was going on inside your own mind even independently of what your relations were to your surroundings at any point so Putnam's twin earth example is meant to challenge this kind of idea so the twin earth example is well imagine that far far away in a distant galaxy there is a solar system just like this one an earth just like this one a US, a California, a Berkeley just like this one and there there is a counterpart of Wheeler Hall and a lecture room just like this one full of bright eager faces thirsting for knowledge just like this one and as you can see twin earth is very like earth I mean really it's very hard to tell on a part except for one crucial detail it's exactly like earth and if you want to take a moment you should check it out I mean can you see any difference? no they really are very very similar yes? ah you reading the caption brilliant well done ok but with that small detail let's just say you can see they're very very similar so you have got a double on twin earth your double right at the moment is molecule for molecule identical to you you raise your hand your double raises their hand you feel thirsty your double feel thirsty molecule for molecule are exactly the same with some crucial differences now suppose that we swapped you in and out for your double would you notice? suppose that right at the moment we can zap you into the seat of your double if you see what I mean we swap you out would you even notice what was going on? is your psychological state the same as that of your double? well sure it is right what would the difference be? if you were swapped in and out you wouldn't tell any difference nobody could tell any difference if you were a headache your double is going to headache if you were feeling puzzled your double if you were feeling suspicious your double is feeling suspicious yes? ok so that's it for twin earth we'll develop the point a little bit further but the key point is there's that notion of psychological state where even though you and your twin are in quite different places surrounded by quite different people and objects what's going on with the two of you internally is exactly the same what's going on in your mind is exactly the same that's the first key point your mind and that of your twin there's no difference between them are we all happy with that? comfortable with that? ok well here is the one key difference between earth and twin earth on twin earth there is a liquid that fills the lakes and rivers that falls from the sky it looks just like water but it's not water it's not H2O it's a very long and complicated formula which for technical reasons I wouldn't go into exactly what it is but we abbreviate it as X, Y, Z so at normal temperatures and pressures H2O and XYZ are indistinguishable you only really see the difference between them showing up when you heat them to something like the temperature of the sun or freeze them to absolute zero you don't really notice any difference regularly alright with that? so although you and your twin are a molecule for molecule identical the liquid circulating through you is different but that difference doesn't show up in the chemical behaviour of the thing so you're still psychologically identical you see what I mean? normal temperatures and pressures XYZ is just the same as H2O the chemical reactions are just the same at normal temperatures and pressures it would take me a little bit more time to see what happens but it's not the same it's not the same it's not the same it's not the same it's not the same it's not the same it's not the same it would take me too far into advanced chemistry to really explain how this works if you really badger me about this then we can make it so that in twin are there really is some H2O but it's too complicated if we drained your me of XYZ of water of H2O and pumped in a whole bunch of XYZ you wouldn't notice any difference nobody would notice any difference a normal temperature unless we heated you through the temperature of the sun you see what I mean? I know that you guys are not chemistry majors so stop me if this is getting too technical you see the scenario? so if you look at a high school on twin earth and you're being taught about the evaporation precipitation the evaporation condensation precipitation cycle it looks just like the one here right? this is very very similar to the kind of diagram high school students on earth get but this is what they get on twin earth so the water was working in the environment the XYZ is working in the environment in just the way that the H2O does here do you want to take a moment to digest that? so here's Putnam actually here he is saying it XYZ is indistinguishable from water at normal temperatures and pressure so you don't have to take my word for it the oceans and lakes and seas of twin earth contain XYZ and not water it rains XYZ and twin earth and not water and so on so if you take a typical I mean this is an actual shot of twin earth you can see that you can see that it looks very very similar to a rainstorm over water on our earth you see the similarity? I mean you can really tell a difference with that than they could I okay so what's going on is that we have a substance which we assume has some particular underlying structure but we might not know what it is but we say it behaves in these ways it participates in the I mean you find it in all the rivers and lakes and so on you see that it's evaporating from the seas and forming into clouds and then blown about and precipitated again you see it's behaving in all those ways you see it dissolves stuff that plants needed to live that you and I needed to live so there are all these behaviours of the substance and you assume that there's some kind of underlying molecular or whatever structure that the thing has that is explaining that behaviour of the substance yep I could elaborate on that idea a little bit but is that plain enough just the way I've said it? so it's not plain enough it is plain enough okay come back to it when you see what happens come back and tell me why you don't believe it so on earth what we find out is the structure underlying these behaviours of the substance is none other than H2O and at that point it's a discovery that water is H2O it's a discovery that gold is the stuff of atomic number 79 these are all chemical discoveries the names of the substances were known for centuries before the actual underlying structure was found but when you say water is H2O that is our old friend and informative identity you're saying it's one and the same stuff water in the H2O you found that out it wasn't a priori it wasn't just something you made up it wasn't just something you stipulated or laid down you found that out so on earth we were using the word water for centuries before we knew anything about molecular composition so when you learn that water is H2O that's a discovery you're finding out what the word water stood for all along you're finding out what that substance really is so on twin earth what goes on is that they have a substance with very similar behaviours to our substance so the S1, S2, S3, S4 here are all just exactly the same and they assume there's some underlying molecular structure here but when they find out that the molecular composition is XYZ they say their informative identity is water is XYZ for them they say that's how they put it and when they say that that's a discovery they're finding out what the word stood for all along they're not just stipulated this they're finding out or an empirical fact about their surroundings that they're expressing by saying water is XYZ okay so you and your twin the points you've got to so far your twin have exactly the same psychological states but you when that moment of revelation comes will say water is H2O your twin will say water is XYZ yep okay here's Putnam's way of expounding the idea for every world one way you could understand the meaning of water is to say well if you take if you put it in terms of possible worlds then take any possible world what is the word water what is our word water referred to relative to some other possible world suppose you said had there been water on the moon there would have been lots of life in the moon what substance are you talking about then in that counterfactual situation are you talking about H2O XYZ something else yeah I mean that's my hunch that whatever counterfactual you express using water you're talking about H2O so one way this is a little bit like this debate we were having about the strangler one way you could hear the word water is as standing for a kind of role that a thing can play so you could say well here plays the watery role on earth and the stuff that plays the watery role on twin earth so you could say here is the local water about the stuff on twin earth and you could say well had there been water on the moon it would actually have been XYZ because the moon doesn't contain enough hydrogen and oxygen to make regular water you see what I mean but the way you guys have just expounded it and I actually agree that's not how we operate in practice we think something like this is not that whatever world you're in water is the stuff that is chemically similar to the stuff that's playing the watery role so the idea expressed here is you point to the stuff that's filling the rivers and lakes and falling from the skies and you say I'll call that anything that fills that role water and anything that's chemically similar to it is water and that chemically similar notion is going to be something that science explains for you ultimately when it gets to down to the nitty gritty and say as well we're talking about molecules here so this way of putting it would be to say water is like a flexible designator is like a description specifying a role wherever stuff plays the watery role but you guys are saying there is something different is going on what you're saying is for every world W when we're talking about some counterfactual situation when you say had there been water on the moon what you're saying is we're talking about stuff that is chemically similar to whatever it is in the actual world that plays the watery role so this is one of these descriptions with an actual in it so is this reading it this way is this rigid or flexible very good any votes for flexible because in order to find out what substance is referring to in any world you have to keep tracking back to the actual world and looking at what's playing the watery role in the actual world so that's really kind of intuitive suppose you ask is it necessary that water is a stuff that fills the rivers and lakes falls from the sky is that necessary yes so in every possible world that's true that's very good actually but is it necessary that's to say look at meditator in all those worlds and one of them in every single world is it water that is filling the watery role sorry yes it's what I I think you're right about the a priori but if you think well the reference is being specified by whatever it is in the actual world that fills that role it could be another possible world I mean there is another possible world in which something else fills that role after all it could have been that all the H2W got drained out of the rivers and lakes here could have been and that some benevolent aliens filled up the planet with XYZ we should do just as well had that happened it would have been something else that was filling the watery role so it wouldn't be in that case it wouldn't be water that filled the rivers and lakes watch me very closely here so this is necessary sorry this is not necessary that's alright if I'm explaining this correctly it should really be pretty easy is this alright it's not necessary that because there could be ringers for water there could be stuff that looked like water but wasn't water right I mean I began by explaining this in a way that's kind of chemically very implausible but really for most kind of substances this is just a general point there could be ringers there could be lookalikes and most things are like that wood is like that there could be a lookalike for wood most animal species are like that there could be lookalikes for tigers most chemical substances are like that there could be lookalikes for most chemical substances so if you can have lookalikes that's to say there could be something else filling that role so it's not necessary that whatever the role is of the chemical or animal or whatever it's not necessary that that animal is filling that role on the other hand is it necessary that water is H2O what a good class on the story I'm telling anyhow it is necessary that water is H2O what is that because in any possible world in any possible world in which you want to find out what water stands for in this world you just keep having to crack back to the actual world and find out what substance the term stands for in the actual world and in the actual world what we happen to know is that it's H2O how is that a priori I don't think I've addressed that yet I haven't addressed that yet I do think it's a priori oh yes I said in reply to this question that it was a priori give me just a second because I agree it needs some explanation and the intuitive idea here is that what makes H2O what makes water the stuff it is is the essence of water is whatever explains its characteristic behaviour if you ask what makes it say that the atomic number of an element is essential to it is that the atomic number of the element explains why the element behaves the way it does so the essence of a thing is whatever makes it behave in just the way it does so it's because all the chemical substances have their particular atomic or molecular constitutions that's what makes them behave the way they do that's what makes them have the temperatures of boiling or freezing for example that they do so in general the essence is what makes a chemical substance the chemical substance it is it doesn't make sense to say I could have the same chemical substance but a different molecular composition or a different atomic number so although looking at this you guys might say look water might be a rigid designator but what about the H2O isn't there a description yes I mean it's describing it has whatever it is two hydrogen atoms to one oxygen atom is none the less a description there's really basic because it's specifying the essence of the substance specifying a characteristic the substance couldn't but have so it is actually rigid in any world in which you get H2O it's the same substance H2O is not a flexible designator so we think of it like that H2O is the essence of water but this last question is it a priori that water fills the rivers and lakes falls from the sky quenches ddoston how about that it's not a priori you said a minute ago was a priori I'm sorry I'm not trying to catch you out I just wish I'm just surprised I'm just talking about what on earth we mean when we say water what we mean in regular English we say water that's very good it's a very good experience to understand what the term is that's right the way you would explain to someone what water is is by showing them some yeah but in general remember with an a priori truth you often need some experience to know what the concept is so if I show you the colours you need some experience of the colours to know what they are that's alright if you consider oranges in between red and yellow that's an a priori truth if you understand the concept then you know the thing is true yes if I followed you I think that's completely correct yes so one way you could think of it is remember bright being the inventor of the wheel remember our old friend bright dearle bright was it a priori that bright invented the wheel yes it was a priori that bright invented the wheel remember the strangler was it a priori that the strangler committed all those murders yes so what you do there is you specify a role and you say whoever is filling that role in the actual world that's who I'm talking about but then it's a priori that in the actual world is filling that role it's not necessary but it's a priori this might be what unlike what I've said so far that's right that's right very good that's very good so you're saying there's some sense in which it's only an accident that the A is hung on this world if the A were hung on that world that's right that's right okay so let me diagram this this is very good so what I've been doing so far is I've been saying let's assume that the actual world is on with the A on it and we don't consider any possibility of variation here and everything I've been saying is completely correct you're not challenging that so long as we've got the actual world fixed and static and then we say what's going on in all these other worlds so the only variation we consider is which of these worlds we're considering relative to this as the actual world but this actually bears on um ah ah right right okay this being a priori the water fills the rivers and lakes whichever world we're in we don't really know a priori of which world we're in if we're in an H2O world or an XYZ world but what we do is we use the word water to stand for whatever it is that in the actual world is filling that watery role yeah that's okay I can put it like that so then you know that well ah if in the actual world if this world is the actual world where the rivers and lakes fall from the sky but had the A been hung on a quite different world had the A been hung on an XYZ world water would still be filling the rivers and lakes falling from the sky quenching thirst and so on had it been a D E F world water would still be filling the rivers and lakes falling from the sky and so on and um had it been um an H well you see what I mean an H I J world right it doesn't matter which world is actual whichever world is the actual one water is still filling the rivers and lakes falling from the sky quenching thirst and so on so it's always coming out true that's how come it's a priori because you don't have to look to see which world is actual in order to know that it's true yep right well the thing there's a sense in which it is contingent that is H2O that water is H2O is not true in the actual world whichever world is actual take this thing here water fills the rivers and lakes and so on alright now you can if you just watch what happens here look you can hang the A on lots of different worlds right and whichever it doesn't matter which world you hang the A on that's true yep that's how come it's a priori water is H2O that's not that doesn't stay true when you move the A around you can see that yes water is H2O changes its truth value if you move the A around yep so it's not true in the actual world no matter which world is actual yep so that's what you mean when you say it's not necessary so I agree that's a sense of necessary right but that's not the definition that we're working with of necessary the definition of necessary under which it is necessary is to say suppose you fix the actual world is it then true in every possible world and it is so given that the actual world is an H2O world is necessary the water is H2O but what happens is that as you move around the actual world casts its shadow over all the other possible worlds you see what I mean so that if the actual world is an XYZ world then it's necessary that water is XYZ it's true in every other world that water is XYZ yep so there's a sense in which it's necessary namely given which world is actual it's true in all possible worlds okay things are hotting up one two three yes that's very good that's exactly the idea that's right in every other so when we do not just say everything which I guess we can talk about the definition of water I'm not dead sure I understand the question I'll say something but then come back and see if I've got it tell me what I haven't got it okay so what I say we know is that is this yep and the way that this reference is being fixed as is as whatever actually fills that role yep so if we assume it's H2O there is actually filling that role then relative to that in every other possible world water is H2O right there is a disconnect but that's because they have two different notions of necessity one is keep the actual world fixed and then look at what happens in every possible world the other is only look at what goes on in the actual world but consider varying which world is actual no sorry no I shouldn't worry every step here is individually very straight forward so if it seems complicated I'm just waiting it correctly but let's come back to this or come up from a different angle well of course you choose the essence of a thing right yeah that would be going too far to say that whatever is actual is true in all possible worlds that would just obliterate the distinction between the necessary and the contingent but when you say what motivates the essentialism here and not quite suppose you think about names of diseases diseases where with a disease you have a certain batch of symptoms that you associate with a disease and then you say but of course you can have a disease without showing any of the symptoms or you can show the symptoms but not have the disease then we think well what it is to have the disease really is having the virus yeah that notion of the underlying thing that is explaining the usual outward characteristics of the thing that's the notion of essence here I'm not sure I have a what else to say except that that seems so intuitive that seems like what we're that's the point of our concept of a disease that's the point of our concept of a substance I mean right from Archimedes with the story of Archimedes let me see if I can Archimedes so this is a long long time ago the king was given a crown by a hostile neighbour and if the crown is made of real gold that's an expression of submission and should be welcomed and if the crown is made of baser metals that's an expression of contempt for war but we don't know which it is and you can't melt it down to which is the easiest way to find out because if it's friendly then that itself would be a declaration of war so Archimedes has to think of a new way of finding out whether it's really gold now that tells you something about the concept of gold you can make sense of finding lists for whether something's gold so if you consider this kind of picture you've got these characteristic symptoms of whether something's gold and Archimedes is looking for a new test and this is the thing about the bath and the density and all that but the important point is here is this is one is two that's not a fixed list like someone trying to find the diagnosis of a disease might always be looking for new diagnostic indicators or whether someone has a disease well I mean if you think about a notion like mud I mean I guess they would have had the notion of mud even in antiquity even the Greeks would have had some notion of mud but nobody in their senses would try to think would sit in the bath trying to think of a new way of telling whether something is mud you see what I mean if it looks like mud then that's it if it fills the muddy role then it's mud but gold is not just looking like gold gold you think is something deeper than that and all through the centuries people have tried to find better tests for whether something is a particular chemical substance and people have always acknowledged the possibility of ringers so the point of these concepts these concepts right from the word go right from the ancient Greeks people have thought I've got these outward indicators of whether something is of this stuff but that's not really what I'm talking about what I'm trying to get onto here is a kind of stuff and my outward indicators are only superficial provisional ways of telling whether I've got something there just as we do with diseases it's kind of very obvious with diseases that's what's going on so something like that is the motive for saying that underlying thing is really fundamental last one three quick things the a priori is that thing that's right that's going to come out true that's right what I'm saying is if you know that it's true in the actual world whichever world is actual I'll go over this next time possibly I'll go over this next time but if you know that it's true in the actual world wherever world is actual then if you think about going from actual world to actual world then if if XYZ is filling this role here then given this world is actual there are going to be these other possible worlds in which H2O is filling that role but H2O is not water so it always comes out contingent whichever world is actual but it also comes out true whichever world is actual that's right I will go over this but really all that's happening here is just what happened with those names like bright and the inventor of the wheel bright for the inventor of the wheel or whatever it is so just to do I have time I would like to just wrap up very quickly so the question was do psychological states fix reference is what's in your mind fixing the reference of your term and Putnam's argument here is let's roll back the time to earth in 1750 nobody has any idea that water is H2O but still back then in 1750 on earth the word water refers to H2O and not to XYZ on twin earth in 1750 what is the word water refer to it refers to XYZ it doesn't refer to H2O but consider you and your counterpart on twin earth I mean not you of course but your ancestors counterpart your ancestor Oscar and your counterpart's ancestor Oscar II on twin earth back in 1750 so suppose it's earth in 1750 and twin earth in 1750 so you got Oscar here and Oscar there are their psychological states the same yes their psychological states are the same are they referring to the same stuff no they are not referring to the same stuff does psychological state therefore fix reference no right psychological state does not fix reference um so the very same psychological states given the qualifications we had earlier they are so far as a massive molecule for molecule identical so psychological state does not fix reference right um that's yeah quick very quickly yes that's right very good so um the last thought that's actually the same point I want to end on that after all what's going on here is that if we switch you between earth and twin earth the reference of your term is going to change yep that's part of the story here but how could you be in the same psychological state if the references of your terms are shifting and isn't what you're thinking about determined by what the references in your terms are and isn't the content of your thought isn't that just part of human psychology and surely what you're thinking about if I say to you well what are you thinking about that's an aspect of your psychology I'm asking you about and if the answer is well I'm thinking about H2O or I'm thinking about X, Y, Z or whatever it might be then you're telling me something about your psychological state so of course Putnam's argument seems like it must be right but then on the other hand it seems like it must be wrong if you see what I mean you see why it must be right because the two Oscars have the same psychological state in a different reference but on the other hand if they've got a different reference doesn't that just mean they've got a different psychological state and you might say well actually we just need a distinction here there's a psychological state that's inside the head and there's some broader notion of psychology that includes your relations to your surroundings maybe we just need a simple distinction like that and in those terms Putnam's point would be the state that was within your head isn't fixing reference but maybe there's some broader notion of psychology that includes your context and that's varying from context to from situation to situation and maybe that fixes reference on those bombshells we'll pick up with Putnam again on Monday ok thank you