 Today is a little bit of an excursion from the main themes because what I'll be trying to do is go a little bit deeper into what Kripi is talking about with rigidity and the a priori in naming a necessity. So I'll start out by just going back over what he says about necessity and the a priori. And then look at, I keep saying these are really central questions we're discussing. We already saw that with Russell, who are just thinking about informative identities and the possibility, whether there can be meaning without reference, can lead you pretty directly to the view that all we can ever talk about at our own sense data. After looking quickly at what Kripi says about necessity and the a priori, I look at what seems to be a fairly direct payoff. Certainly Kripi thinks it's a fairly direct payoff for the mind-body problem. And then we'll go on to look at the notion of the actual world and how that might connect to the a priori, how you might explain what it is for something to be a priori. But let's start out just reviewing necessity and the a priori. So necessary means something like true in all possible worlds. When you're talking about necessity, you're talking about what could be, what might be, and you don't mean that just so far as you know. You're talking about what could have been, what might have been. Yes, remember that distinction between wishing you spent the day in San Francisco and thinking you might actually have spent the day in San Francisco. Yep, that's all right. Okay. An a priori has to do with knowledge. I said this notion of necessity here doesn't have to do with knowledge. A priori does have to do with knowledge. Can be known otherwise than on the basis of experience. You don't need experience to tell you that this is true. Okay. So we have the actual world and we have our old friends, all the other possible worlds. Some closer to the actual world than others. And of course this is only a small sample. So necessary means it's true in the actual world and true in all the other possible worlds too. A priori just means you can know that it's actually true. You can know that it's true without having to know anything else about, having to know on the basis of experience anything about which world you're in. See these seem like different notions. So if you take Hesperus, is Hesperus, is that necessary? Conclass, is that necessary? Yes, that is necessary. Is that a priori? Yes, that is a priori. Yes, you don't need to think too hard about that one. Hesperus is phosphorus. Is that necessary? Yes, two rigid designators. Yes, designating the same thing in all possible worlds. So it's going to be necessary if it's true at all. Is it a priori? No, that one is not a priori. Isn't that wild? How could that be? Kripke extends his approach to talking about statements involving substances or general terms saying things like heat is motion of molecules, pain is C-fiber firing. These are identity statements. We don't involve names for particular individual objects. But if you think that heat is a rigid designator and motion of molecules is a rigid designator, then heat's motion of molecules is going to be necessary. Yes, right, very good. And if you think pain is a rigid designator and C-fiber firing is a rigid designator, then you're going to think that this statement is necessary. And really on the face of it, they do seem to be rigid designators. What I said about Al Gore was as you consider a counterfactual when you're saying if Al had only won that election, then what you're doing is you're talking about what happened to that very person in these different situations. If you say if heat, if there had only been heat on the moon, then you're talking about that very phenomenon, heat, the very same thing. If you say if octopuses had been able to feel pain, then you're talking about that very phenomenon, pain in some different counterfactual scenario. So these terms do seem to be rigid on the face of it. So if you've got, but these are obviously not a priori. Are these a priori? No, these are not a priori, right? These were found out as a result of extensive work, if indeed they're true. So if you get Hesperus being rigid, then Hesperus denotes the same thing in every possible world. Phosphorus is rigid, so it denotes the same thing in every possible world. So if they denote one and the same thing in any possible world, then they denote one and the same thing in every possible world as each other. So the identity is necessary. This is your last chance. Are you extremely comfortable with that? Well, it's not actually your last chance, but okay, it's a chance. There's one chance among many to pause here. So Hesperus' phosphorus is necessary but not a priori. Consider, we talked a little while ago about if you're talking about who invented the wheel, presumably there was some individual who invented the wheel, unless it was done by a committee, but let's suppose that there was just some one individual who invented the wheel and we call that person bright. Now, consider the question, is it necessary that bright invented the wheel? No, it's not necessary. Bright could have been crushed at birth. You can imagine a different possible world in which there was an asteroid shower just as bright was born and wham. That's it for bright. No inventing the wheel. Someone else had to do it. Yes? The march of civilization was delayed by several centuries, but there you go. That makes sense, right? So it's not necessary that bright invented the wheel, even though bright did invent the wheel, right? But so if you consider bright there is a rigid designator, the inventor of the wheel is a flexible designator. There are other possible worlds in which it was, or someone else got there first, and bright wasn't the inventor. Bright was simply trudging along in the rear. Yeah? So bright's a rigid designator, the inventor of the wheel is flexible, so bright invented the wheel is, um, necessary or contingent. Contingent, very good. Okay, but is it a priori that bright invented the wheel? Well, I just told you, look, whoever invented the wheel, let's call them bright. Yes? So are you really going to put forward this hypothesis? But maybe bright did not invent the wheel. It's like, yeah, I mean it's like that thing. Let n be the number of cows in the field. But sir, sir, suppose n is not the number of cows in the field. I don't know how much I need to go over this. I just explained what bright meant by saying it's the inventor of the wheel. Yeah? Now we all agree that's contingent, but it is a priori. Yeah? I mean, suppose you consider a real case. Suppose there's, I think we talked about this a bit earlier actually, suppose there's someone who's murdering a lot of people in a particular area, and the police say, let's call this person the strangler. And if you're a hopeful young police officer, if you're a hopeful young police officer, then you might put forward hypotheses like, maybe there's no such person as the strangler. Maybe there are many people committing these murders. But it hardly makes sense. I mean, you're not going to get very far. If your big idea is maybe the strangler was framed. Maybe there is someone person committing all these murders, but it's not the strangler. If anyone's committed these murders, it's the strangler, right? That's a priori. You see what I mean? That is not a bright idea. Maybe it was someone else. But is it necessary that the strangler committed all these murders? Well, no, your honour. I mean, if only he'd had breaks. If only he'd been brought up right. He wouldn't have had to fly. You see what I mean? Or if only there had been an asteroid shower. He wouldn't have committed any of them. But if anyone did commit those murders, it's the strangler. That's a priori. So it seems like in other possible worlds, where the strangler was hit by a meteor or whatever, something did in fact strangle all those people. And it seems like if you just pick out the term strangler to denote the person or whatever that is responsible for all those stranglings, then it seems like there can't be any world in which the strangler, whatever that is, is not the person or whatever responsible for the strangler. Ah, right. Well, I don't really see that. Suppose you consider the situation in which the strangler had a happy childhood. So let's suppose it was miserably unhappy. And over here, here he is smiling, cheerful, a joy to all around him. Now, in that world, it's one and the same person, this strangler we're talking about. But does he commit any murders? No. Ah, but we're talking about this guy, this strangler. You see, it's so unfortunate he went wrong. He could easily have gone right. If people hadn't been so mean to him. I mean, I'm sorry, I don't want to get too sentimental here. The issue I see with that is that we're using, we derive the name the strangler just by denoting whatever it is that's responsible for all the stranglers. So it doesn't seem like the reference of the strangler is fixed to any one person that might be different from another possible person. But that's the point, really. If you just hear the way the language is used, if you are the criminal psychologist on his case, then you might ruminate and say, the strangler is someone who's had a lot of unhappiness. If only the strangler had been treated right. In a real sense, the strangler is a victim too. I mean, here you're talking about what would have happened in these other worlds to that person, the strangler. And saying in those other worlds, he wouldn't have committed all those crimes. Yeah, he would, he's one of the same. He wouldn't meet that description, but he'd be one of the same person. Let's time out just for a second. Yeah, yeah. I'm having a similar problem because it seems like the strangler if Bob is the strangler, then Bob may not have committed the strangler. Yeah, so I'm talking about the strangler committing the murders. It's a name whose reference is fixed by a description. And as such, it's rigid. So that is, that's say for your idea. Okay. For the name for the man, it seems like the man could have not committed the murder. Right, that's right. But what I'm saying is when I say the strangler, I'm rigidly identifying the man, assuming it's a man, yeah. Well, rigid has to do with what goes on in any world. That's not a priori. Uh, yes. Okay, you could just read that off. They're both rigid. We are going to think about this a lot more actually today. I thought someone else had a hand. No, okay. Are you happy with that? No, I can see that virtually no one is happy with that. Sorry? Yes, what about it? Same as the identity across the world. Yeah. Well, I think lots of our emotional life supposes that you can make perfect sense of identity across possible worlds. You can say, if only I'd had a few, I thought it was too sentimental this morning, but I can say if only I'd had a few lucky breaks, if only they'd given me a chance. Yeah, I'd be all right. You see what I mean? You can do that. Yeah, or if only I hadn't done this. Yeah. Or I nearly did that. You think, wow, what a narrow escape. Well, there you're all talking about possible worlds and assuming it's you in all of them. Yeah. So if these kinds of reflections make any sense at all, then identity across possible worlds has to make sense. Yes? Good, yes, yes, yes. Right. Well, what about this? Suppose you thought of it like this. Suppose you said, well, when I say bright is the inventor of the wheel, really you should see that as meaning whoever actually invented the wheel. And what that means then is to find out what bright designates in any possible world, what you do is you look at the actual world and you see who invented the wheel in that world. Right? And then suppose I'm asking about what's going on in World 17 out in the edges, yeah? Then I say, what was bright doing over here? Well, to find out who bright is over here, what I do is I track back to the actual world and I look at whoever it was in the actual world invented the wheel and I see what they're up to over here in 17, which might be not inventing the wheel, they might simply be wasting their time. Yeah? So if you think, well, what goes on with the inventor of the description, the inventor of the wheel is, if you want to know who it designates in World 17, then you look at who invented the wheel in World 17. But if you want to know who bright designates in World 17, you don't just look at what's going on in World 17, you have to trek all the way back to the actual world and look at who invented the wheel there. And that will get you the outcome that it's contingent that bright invented the wheel because bright is going to be rigid because I said this for World 17, but of course for any world, let it be World 234. What do you do to find out what bright stands for in that world? Well, you look back to the actual world, you find out who invented the wheel in the actual world, and then you track back to World 234. So for every world, you get the same strategy for finding out who the name bright designates in that world, namely, trek back to the actual world and find who invented the wheel in that world. So bright has got its reference fixed by this description, but it's relative to the actual world. So it's always referring to the same thing in any possible world, whereas this description is varying what it designates from world to world. So it's going to come out apiorei that in the actual world, bright invented the wheel, but contingent because bright might not have invented the wheel. There you go. It's kind of like a conjuring trick, but yes. That's right. The stronger it is, whoever actually committed those models. Very good. Okay. I'm sorry. Someone else? Yes? Yes. No? Well, you see, I just introduced bright as a name for whoever invented the wheel. That's right. I just said that someone must have invented the wheel. Let's call them bright and now we can speculate about what bright must have been like. Yeah. But with Benjamin Franklin, I'm not saying someone must have invented the bifocals. Let's call them Benjamin Franklin. That's not the way it's working there at all. Yeah? Once you identify them and you realize that everyone else calls them Ig or whatever it might be, then that's probably what's the word I want. It's not some kind ofism. It's some chronoism. I mean, making a pejorative remark about people from another era. Okay. Anyway, whatever they call them then. Yeah. That name you gave on direct contact with the person, that's not likely going to be descriptive like this. Yeah? But I'm just saying, so long as we're working with a descriptive name like bright or the strangler, then you get this phenomenon. You get something that's a priori but not necessary. Look at that. So there you are. Brightness. So, hispirus is phosphorus is necessary but not a priori. Bright as the inventor of the wheel is a priori but not necessary. Happy with that? Yes? Comfortable? No? Yep. That's right. We're only talking about metaphysical possibility here. So the point is that this kind of metaphysical possibility, when I say that I just mean it doesn't have to do with what might be true so far as for all you know. This is only talking about metaphysical possibility and the point is that metaphysical possibility comes apart from talking about what's a priori or not a priori. Why is it necessary that Bob is a strangler? Actually, did I say? Oh, I didn't say it was necessary. Yes? Right. Well, think about it like this. Suppose I'm saying, think about the strangler in the world where they were crushed at both. Right? Yeah? Now suppose that the strangler is Bob. Is that a world in which poor old Bob got crushed at both? Or did Bob live a long and happy life? Sorry? Did Bob get crushed? Okay. So Bob in that world is crushed and the strangler got crushed. But was that a coincidence? No. No, because they're one and the same person. Right? Even in this world. Yep. But the same is true of every other possible world in which they both exist, Bob and the strangler. Now in the world in which Bob is crushed at both and the strangler is crushed at both, no relevant strangling occurs. Yeah? Because they didn't get the chance. Right? So any strangling is being done by someone else. But you could say that Bob and the strangler are going to co-designate in every world you look at. If there's a world in which the strangler got to be CEO of a very large company, then that's a world. Did Bob get to be CEO of a very large company in that world? Of course he did. What do you think? Do you think he just got halfway up the ladder? It just doesn't seem necessary. It seems like Bob and the strangler could designate things in people. But if you buy it, the strangler is rigid. Well, if I buy that, if I suppose that, I don't see why I have to suppose that. Okay. It's okay. We'll cut, yeah. The president was assassinated today. That doesn't mean it's all other possible worlds. Barack Obama was assassinated. That means it's the man who was assassinated other than Barack Obama. Ah, yes. Right. So that seems to go against you. Ah, that's what I don't see it. If I say the president was assassinated today, now I talk about some other possible world and I say, okay, so there's a possible world in which the president is Arnold Schwarzenegger. Schwarzenegger would never have let himself be hit like that. Right? So I say, if only Schwarzenegger had been president, then we'd still have a live president. Yes? No. That's right. Well, I didn't, yeah. Okay, I'm using the strangler as a name. Yeah. I realize, okay, I suddenly realize that's what, that's possibly the one misleading thing in the way I'm setting this up. Let's just call him, well, what should we, the rooper, yes, right? It's not meant to be understood as a definite description. It's meant to be understood as a name. Yeah. So it's just an accident that there's a vet in there. Okay, okay. Yeah, okay. I'll have to think about that. Okay. Why is it so natural to put the vet in there? Okay, fair enough. Okay, you haven't raised a question yet. So one, I think this is probably worth carrying on the discussion with, is that right? Because I think you guys, you guys are raising questions on that alone. You haven't raised a question yet. Are you going to raise a question? Yes. Okay, so. Yes, that's right. Well, the proof is, remember what I was saying about Al Gore? Yeah. If Al Gore had been president, had been elected president, the argument is really just an appeal to how an ordinary speaker evaluates these kinds of counterfactuals. Yeah. So what I'm claiming is that we can all make sense of counterfactuals like had Al Gore been president in 2002. Yeah. Or in this case, if you say, I say we can all make sense of conjectures like had Bright not invented the wheel, would someone else have done it around the same time? That kind of question makes perfect sense. You see what I mean? If you believe that history is made by great individuals, then you will say, well, had Bright not invented the wheel, it might have waited another couple of millennia before the wheel was invented. Or if you believe that great inventions are the result of historic forces and the individual just kind of bobs up and then you will say, had Bright not invented the wheel, someone else would have around the same time. So the proof, such as it is, is these kinds of points about how you interpret counterfactuals, what the right interpretation is, what the right way is to hear these counterfactuals. As I said, this is kind of descriptive linguistics. This is a point about how we actually use language. But one way of backing it up on this point about Bright and the Strangler is just to think about what I was saying about the way the word actual actually can work, when you say the actual inventor of the wheel. This is explaining how these terms could have those characteristics. So there's a model here of how all this could be happening. One, two. Yes. Bright is it, wait a minute. Bob invented the wheel. I'm sorry. Right. No, this is a confusing thing. This is what's confusing in what I've been doing. Bright, sorry, Bob is the Strangler, is two proper names. That the is an accident. Whereas Bright invented the wheel is a name in the description. I don't see why that's not okay. But your intentions can determine whether or not the term is being used rigidly. So here I could introduce a term just as short for the description. I think that was truly confusing about the way I set things up there. I do see that. But what I was suggesting was that in ordinary talk, when we use a term like the Strangler, you can make perfect sense of these counterfactuals. When I say the Strangler had a few bad breaks, otherwise he'd have been fine. You see what I mean? Those counterfactuals seem to make perfect sense in the way we ordinarily talk. Therefore, Bright is therefore the Strangler is not being used just as an abbreviation for the description. But you could use a term just as an abbreviation for the description. I think that probably is a matter of intention. At that level, you get to decide how you introduce the term. I think that's what was genuinely confusing in the thing I said earlier. I always thought that Kripke thought that a name just designates an object and was not fixed by the definite description. That's right. I heard fixed by the definite description. That's right. Kripke didn't really go very deep into this kind of name in his discussion. The following is a kind of qualification of what I just said about intention. If you have a picture on which you have the name, you have the object, and you have something like a sense of the description, fixing the reference. So suppose you have that kind of picture. Then you really do seem to have a choice as to whether you regard the name as truly a rigid designator, the way I've been suggesting we do with Bright. Or you could, just as a matter of intention, keep it flexible. That seems possible. But suppose that you have a causal theory of reference where you have the object causing the use of the name. That's what it is for the name to refer to the object. Then if you have a name functioning like that, then could it be anything but rigid? I mean, I think Kripke's intuition is it couldn't be anything but rigid in that kind of scenario. If there's just the object and the causal connect with the object, giving the name significance, then if you subtracted the object, there wouldn't be anything left to constitute the name having the same meaning but a different reference. So intuitively it seems like if you've got a term whose reference is being fixed by a causal chain and not by a description like this, then it can't but be rigid. But that's not what's going on here. It's showing that you can have that mirror image of what Kripke thought of the Hesperus's phosphorus case where necessity and a prioricity are coming apart. Now, Kripke does discuss examples like the standard meter in Paris and gave examples. He didn't discuss this particular case, but what Kripke did discuss was examples like, I don't know if it's still true, I don't suppose it is true anymore, but there used to be in Paris a bar kept at the right temperature that was the standard meter and everything else gets measured by reference to it. So suppose you say is the standard meter one meter long? Well, sure it is. Is that a priori? Sure it is. Is it necessary? Well, no, because if the electricity had gone out, the thing would have shrunk or expanded. If you do got blowtorch to it, it would be a different length. It wouldn't be a meter long. So it's a priori that the standard meter is one meter long, but is it necessary? No, I mean, you might have taken that very bar and teased it out, so it was a mile long. A mile is much longer than a meter. So it wouldn't have been a meter long. So what I'm saying, I'm giving this as a very simple version of where you can, in some sense, you can see very clearly what's going on. I mean, I realize that there's a level at which this is fairly confusing, but it's meant to be simple enough that you can see all the pieces, you know, you can see just what is happening. And I think it's the same structure as the case that Kripke does talk about, namely the standard meter. So you can think of the name, the standard meter, being introduced as the length of that bar in Paris. The meter being, yeah, coming. So that's right. And that one, and so I don't see why the name's right, because if it's fixed by the definition, the definition is flexible. Okay, well, that goes back to this exchange about, does it matter, does intention matter? Yeah, so on the one hand, I think intention does matter, because what I was saying, it could go either way. You can make sense of it being rigid, and you can make sense of it being flexible. But what I was also saying was that when you introduce a name like Bright or the Strangler, then we actually do talk as if these names are rigid rather than flexible, because we do make sense of things like, questions like, suppose Bright had not invented the wheel. Would someone else have done it? Suppose the Strangler had been better brought up. Would someone else, was someone else waiting in the wings to commit those murders? These seem to make perfect sense. Suppose I say let N be the number of cows in this field. Can't I make sense of the possibility that after all, if there had been an outbreak of mad cow disease, there wouldn't have been any cows in this field at all. And N would not have been the number of cows in this field. If there are four cows in the field, and I say let N be the number of cows in the field, then N is four. But four might not have been the number of cows in this field. If there had been an outbreak of mad cow disease and it had all been slaughtered. So it's not necessary that N is the number of cows in this field, but there is a priori, because I couldn't have made a mistake about that. This is a still further kind of case. That can happen, but I was assuming that in this case it's not happening, and I think in the case of the strangler, that doesn't happen. Right. Okay, I see what you mean. It's a bit of gas that you use to lock on to the right object. That's perfectly fair for how I was talking about across possible worlds. But in the context of the ongoing police investigation into the whereabouts of the strangler, we don't throw it away. So if we're just thinking in the actual world about trying to find this person, then we don't throw the description away, because that's the only fix in who we're talking about. But you're right that when we're talking about what could have happened in other possible worlds, they were just locked onto the person and then in that context we're forgetting about the description. Okay, I have a lot more to say to you on this subject, but I guess we'll have to postpone it until Monday. Are there any last questions, or is there anyone who wants to sort it all out just before we go? I mean Wednesday. When I say Monday, I mean Wednesday. Of course I don't know. Monday could have been... No. Okay, well, that was solutory. I'll sort it all out and add some further reflections on Wednesday. Okay, thanks.