 So the last time we ended with our civilisation crumbling around us, and today we face a heavy responsibility. So Pryor's article makes a very, very simple point, but as so often with these very simple logical points, it really has a lot of resonance, it's very far reaching the point he's making. So what we've been doing so far in looking at Wittgenstein is shaping up to throwing out the idea of semantic value, throwing out the idea that notions of truth are reference, what the sign stands for, the contribution the sign makes to the meaning of a sentence containing it. That has anything to do with notions of truth or reference. So in the case of knowing what it is for something to be round, for example, the idea is that if you give yourself a verbal definition, or if you give yourself an image of roundness and say that's what I mean by roundness, that can't be what drives your use of the term round. To characterise your use of the term round is better just to think in terms of the inputs to you making the judgement that thing is round, what kind of perceptions would lead you to make the judgement that thing is round, and what the implications are for action of you making the judgement that thing is round. And forget about the bit in the middle, that doesn't do any work. You can't derive that way of using the sign from merely having the image. Two different people could both have the same image in their heads, but keep using the sign in different ways. Okay, that's the point we've gone over many times now, is that? I mean, do I need to labour that anymore, or is that pretty straightforward at this point? Okay. Well, that's in general true for names. We don't need the notion of the object that the name refers to. We just need the inputs to our use of the name, and what implications we draw from our use of the name. For predicates, we don't need the idea of a map from objects on to truth or falsity. We throw that out for propositional constants like and or or. The semantic value there is not the object it stands for, it's not a map from objects to truth values, it's a map from truth values to truth values, and we throw that one out too, right? So we just throw out semantic value altogether. And the argument is the same in all cases. Just by being given the truth table, you can't derive the rules of inference for a term. You already need to know how to reason logically to get the rules of inference from the truth table. So forget all that stuff, and just characterise for and, you just characterise the meaning of and using the input rules and the output rules. So the input rule is if you get A and you get B and you get A and B, so you get Rolly Smokes and you get Isaac Fishes, and then you get Rolly Smokes and Isaac Fishes. That's all right. Let me just lay that down. That's fixing the meaning of and. And if you get A and B, you've got A. So that's the output rule. If you've got Rolly Smokes and Isaac Fishes, then you've got Rolly Smokes. And can you guess what the other output rule is? Yes, you've got Rolly Smokes and Isaac Fishes, then you've got Isaac Fishes. Okay, and then you've explained the meaning of and. And if you operate that way, if you use the sign that way, that's all there is to your understanding of the sign. Okay, so that's a full characterisation of the meaning of and, and you don't need any talk about truth or falsity here, any talk about reference, anything like that. That's really, I think, the natural way to read the upshot of what Wittgenstein's doing, talking about following a rule. There is only the use of the sign. Talk about what it means in any sense over and above this is just idle. Now if we do this for A and B, can we do it for R? Yes, we can do it for R. What's the input rule? If you get A, you get A or B. And if you get B, you get A or B. Right? What's the output rule for R? If you get A or B, what can you conclude from that? Can you conclude A? No. Can you conclude B? No. Can you conclude anything at all? Well, you must be able to conclude. Sorry? You can conclude A or B. Yes. Thank you. The way we actually work, let me put it to you, is the reason like this is you get A or B, and then you say one or the other, A or B, and then if from A you can derive C, and if from B you can derive C, then you can say, well, look, either way, C. You see what I mean? You know it's one or the other, and whichever way it goes, you get C. Therefore, from A or B, you can conclude C. So if you say, look, either Romney wins or Obama wins, I mean, presumably, prior to the election, people were sitting in smoke-filled, well, maybe not smoke-filled, committee rooms are going through just this kind of reasoning. If either Romney wins or Obama wins from Romney winning, it follows that UC will need more money. If Obama wins, UC will need more money. So either way, what conclusion follows? UC will need more money. Please give generously. Okay? No, that's by the way. That's how you reason with all, right? Either way you say C, therefore C. You see what I mean? Yeah. So that's how you state the output rule for all. And the thing is, you might need some other premises. That's to say, when you're arguing from Romney winning, it follows that UC will need more money. You might need some other premises, right? It's not just because Romney wins. There might be other factors on play, meaning that UC will need more money. So call them X and Y. And then if from A or B, together with the hypothesis of X, and together with the hypothesis of Y, then from A you can derive C, and from B you can derive C, then forget about the A and B here. C follows from A or B, together with the other premises, X and Y. That should be very simple. If it doesn't seem very simple, then I'm not explaining it correctly. How does it seem? You give me that one? So if I do that, then I've characterised the meaning of R without talking about truth or reference or anything like that at any point. So that's throwing out semantic value and just describing use. It's doing it now for and or. So now, what about criticising the use that you make of a term? If you think about Descartes and skepticism, then Descartes really seems to be operating with the idea that he knows what it is for all the propositions he understands to be true. He just doesn't know if he's using them in the right way. I mean, he knows what it is for there to be a hand here, for there to be a table there, for there to be other people around him. He knows what it is for all those things to be true. He just doesn't know if he goes about verifying them in the right way because he uses his sense impressions. And his question is, do my sense impressions really give me a good way of finding out whether things are that way? I mean, the analog for a logical constant would be to say, well, I know the truth table for and or or, but is this really a good way of finding out whether a or b is true? So once you know what it is for a sentence to be true, you can start to challenge your ways of finding out whether the sentence is true or whether the truth of the sentence really has the implications you take them to have. So that's what Descartes does. He says, well, I know what it is for there to be the regular world around me, but maybe my usual ways of finding out are no good. So if understanding a sign means knowing what has to be the case for sentences containing that sign to be true, that's the objective of your way of finding out. Your way of finding out is going to tell you, is that thing true? Your way of drawing implications is going to be what follows if that thing is true. Then like Descartes, you can criticise the ways, the use that you usually make of the sign. You can say, maybe I'm not using it the right way. So you've got your input to applying the term. You know what has to be so for an application of the term to be right, and then you've got your output. You're drawing your conclusions from that. But the picture here is that knowing what has to be so, and this is a natural way of thinking of it, if you've got your ways of finding out whether a sentence is true, then the truth of the sentence is the objective of this procedure. Finding out whether you're doing things right here, that has a point. His point is to find out whether this thing is true. Let me give you a parallel here. Suppose someone says, look, I play lots of bridge. I love playing bridge. Someday I'm going to be rich and famous because I play so much bridge. Then you can argue with them if they say, well, why are you playing so much bridge again? Because it's going to make you a lot of money because it's going to make you famous. And you can say, that's crazy. There's only a handful. I don't wish to be disrespectful, but you might say there's only a handful of cranks in the wall after you play bridge. You're never going to get famous or rich doing that. I mean, how much money do you make doing it anyway? And you could check, right? But on the other hand, you could have someone who is just a bridge nut. They just wake up in the morning and they think of that as drawing their hand for the day, and they spend the whole day dreaming about their next game. And they just play bridge for its own sake. And if someone is doing that, then you can't really criticise or justify it. I mean, everything else in their life is just about allowing them to play more bridge. You have no leverage against a person like that to say, why do you play bridge? He does everything else in order to play bridge. Playing bridge doesn't have some further point for him. That's the point of everything else. So if someone is doing something just for its own sake, you have no leverage to justify or criticise it. But if they're doing it for some further point, then you can say, how am I going to justify or criticise it? Does it get me that point? So if you've got the notion of the truth condition of a sentence as specifying the point of what you're doing and you're trying to find out if it's true or not, then you can criticise or justify your ways of getting that objective. So Descartes' kind of scepticism says, are the ways we use to verify statements really good ways of finding out whether they're true? But suppose that with Wittgenstein you just throw out the idea of semantic value. You throw out that notion of truth or falsity or reference and say there's only the use. All there is is just our ordinary practice of talking the way we do. Then there is no point that is meant to be serving. There is no objective that is meant to be getting you. That's all there is. You can't criticise the way we ordinarily talk. You can't do the thing Descartes was trying to do of criticising the use of the term. So if you've got something like this picture, your ways of finding out whether something's a cube and your image of a cube is telling you what it is really to be a cube, then you can say is that really a good way of finding out whether something's a cube? But if that truth condition has gone, then there's no possibility of scepticism. You just talk the way you do. That's what it is to assign a particular meaning to the sign. Similarly, if you've got these rules for and or for or, then there's no way of justifying or criticising them. The thing is that that's really quite general. These are very artificial lab examples, but often enough there's such a thing as bits of language that people find offensive and say you ought not to talk that way. And we do say things like you ought not to use notions like, well, I don't want to start some conflagration, but right now there's a whole string of words that if I used any of them, it would just make you see red. Suppose you take an ocean like Rich. If Wittgenstein is right, there's no way of criticising our technique or custom or practice of using an ocean like Rich. So if you come upon a community that just has this as the input rule for which X floats when pushed into water, right? And that's your input rule for which. And your output rule for which is from X is a which so you can conclude X should be bummed. You have no way of criticising that, right? That's all you can say is this is the way of my people. This is the use we have for the term which is not something that can be justified or criticised. It makes no sense to be sceptical about this notion. So that is one somewhat disturbing consequence of Wittgenstein's approach. If all there is to learning the meaning of a sign like which is learning a custom or a practice or a technique then you have no way of criticising the custom or practice or technique. But I mean this is close. The way I put it there is very, very simple. But that's close enough to real life examples to make you think can't you criticise? Is it really true? You can't criticise a way of using a term. Now Wittgenstein's, sorry, prior's example of tonk is a really simple laboratory example where things seem really to be going wrong. Yeah. So let's just lay out what tonk is. The general background to what prior's discussion is Wittgenstein saying things like a person goes by a signpost only and so far as there exists a regular use of signposts, a custom to understand the language means to be a master of a technique. There's no way of grasping the rule which is not an interpretation. That's to say it's not a way of saying what it is for the use of the term to be true or false. But it's just exhibited in what we call obeying the rule or going against it in particular cases. So suppose you've got a technique or a custom or a practice of using the sign tonk in the following way and I'll ask is there any possibility of criticising it? So the input rule for A or B was from A you can get A or B and from B you can get A or B. So that's the same as the input rule for tonk. Okay. From A you can get A tonk B and from B you can get A tonk B. Watch me very closely here. That's all right. I can define the term like that. That's the way we use it. Okay. So from A you can get A tonk B. So from Rolly Smokes you can get Rolly Smokes, tonk, Elvis is alive. That's all right. That's just the way it works. That's the way it all works. So it must be all right for tonk to work like that. Now you now consider the output rule for A and B. Well that was from A and B you can get A and from A and B you can get B. So the output rule for tonk is just like that. From A tonk B you can get A and from A tonk B you can get B. So if you get A tonk B, if you get Rolly Smokes, tonk, Elvis is alive, you can conclude Elvis is alive. And then vigorising thought. Right? Okay. So that's the introduction rules and that's the elimination rules. So this is just like any regular logical constant. This is just how you explain the meaning. That's all there is to explaining the meaning, right? We don't have any notion of semantic value. We don't have any notion of truth or falsity. We're just describing the use. We might come upon a people, some little known tribe of logicians somewhere, who use tonk exactly that way. And that's all there is to the sign having a particular meaning. It's got that regular pattern of use. And the pattern of use is perfectly well defined. So suppose you have Rolly Smokes. Then from Rolly Smokes you can infer Rolly Smokes, tonk, Elvis is alive. That's all right? And from Rolly Smokes, tonk, Elvis is alive. You can infer Elvis is alive. So from Rolly Smokes you can infer Elvis is alive. But notice that Rolly Smokes and Elvis is alive here. There could be any two arbitrary sentences. Yeah? So suddenly from anything I can infer, anything. Yeah? If I say there's a sparrow in the grass, I look out the window, there's a sparrow in the grass, there's a sparrow in the grass. Tonk Romney is president right now, today. There's a sparrow in the grass. Okay, so I've concluded that. That's all right. There's a sparrow in the grass. Tonk Romney is president. Therefore Romney is president. That's just the elimination rules. So I've proved that Romney actually is president. Okay? You guys are used to shocks in this class. We should tell Fox News. Let's just go over the reasoning here. Okay, suppose there is a sparrow in the grass. Yeah? I mean I can make it something else if you like. I mean suppose there's a laptop in the table or there are people on chairs. From that you can infer there are people on chairs, Tonk Romney is president. And from there are people on chairs, Tonk Romney is president. You can infer Romney is president. So you've proved that Romney is president. Is there any kind of weak spot in the reasoning? Okay. Sorry? Notice how powerful the technique is. Suppose you made it Ron Paul is president. There are people in the chairs. There are people in the chairs, Tonk Ron Paul is president. There are people in the chairs, Tonk Ron Paul is president. Therefore Ron Paul is president. And that works too. They must have some power sharing. A great fit. Is there a weak spot in the reasoning? Yes? One, two. Is there a weak spot that lets you prove anything? That's right. I could prove contradictions. I could prove that Romney is not president. Right? And then what you mean is a weak spot though. I mean it just displays the power of the technique. I mean just saying you don't like the results isn't to show that there's something wrong with the process. Yeah? Well here's the definition of Tonk. Here's the whole story about Tonk. That's the input rule and that's the output rule. Yeah so it's perfectly coherent. It's perfectly well defined. Yeah? So there's no problem with the reasoning. Don't say you don't learn anything in this class. I mean how valuable this will be to you in your everyday life. That's right. And a very short space of time too. And from minimal premises you just need Tonk. Right? Yeah. There's a problem with the conclusion. The Romney is president. Yeah. You might just be reading too much of the mainstream media. It can't be right. But okay but if there's a problem then where is it? This is perfectly well defined, right? Okay so I take that Tonk as being used correctly here. But what if one rule say Tonk doesn't allow us to use another rule correctly? So something like early explosion. Do you mean by the explosion? I think you meant you can prove anything. Right. Okay so there's an explosion. But then we have something like Tonk that doesn't allow us to obey that rule. So we have a conflict of rules. Such that one of them can't do that. Right. There could be conflict in your system of rules. Yeah. Well that might happen. That probably does happen actually. But the question then is how do we, what are the principles for resolving it? We need some kind of trade off. I mean the kind of trade off you get might be well, be careful when you're using Tonk. Right. Just don't use it for political purposes. Use it only to prove things about what's going on in outer space. That would stop the conflict. Use it judiciously. Use it wisely. It does seem that well, yeah a custom might be a complex thing with lots of moving parts. What you're saying is a custom might have things that force you to make accommodations, internal accommodations. But you could make all those internal accommodations couldn't you? And still keep Tonk in play. You could say well we're only going to use it to prove results about what's going on in outer space. And the first person to use Tonk to establish any particular result has the field as it were. So if someone comes up later and proves the negation, well that doesn't count because they were second. That'll be all right. There wouldn't be any conflict there. That would contain the explosion. Okay, so that seems, yeah? Hold without experiencing it. If I have like a banana and an apple, like the influence rules are formalized. If I have a banana and an apple, I know that I have an apple and I know that I have a banana. Okay. That we're experiencing where that would. But how does it go for A and B? I mean, if the rules for A and B are whatever they are, like that, right? I mean, how does that relate to experience? Are they grounded in experience somehow better than the rules for Tonk? And then you have the first thing, you have the second thing, and you kind of focus on either one of those. Right. Well, you can focus on either one of them. I mean, unless you mean more by that than I'm grasping. Okay, come back to that. He was right, but I mean, like conditional. I can say if the sky is green and my hair is blue, neither of those are true, but that conditional is clear. Right, the conditional, yeah. There doesn't seem to be any sense of which is grounded in experience. Is that? Yeah. And with the apple and banana case, with an apple and a banana, I could, couldn't I, suppose I have an ocean of Bapu, right? So the input rule is, I just got one particular banana and apple in front of me, so I can say the banana is F, the banana is bright yellow, right? So I can conclude from that the Bapu is F, and if I've got the Bapu is F, then I can conclude from that that the apple is F. I'm not defining it. I mean, that's the rules. I told you the rules, right? The input rule is from the banana is F, I can conclude the Bapu is F, and from the Bapu is F, I can conclude the apple is F. That's the input and output rules. That's all it is to the use, right? That's the whole thing about the, I mean, you're right. That's the intuitive thing you want to do. That's what I'm talking about, right? But the whole point about the Vickie sign is we're throwing out the notion of very definition, very bit in the middle of the controls, how you use the term in these cases. And once you've thrown that out, why can't we do this? I love any pattern of use I like. Yeah, because there's nothing, there's no contract with which I have to keep faith. No need to lay down what the thing means. Consistency, yeah. These are two different ideas, consistency and some conception of what it is, right? Consistency you could get by the thing I was suggesting about confining yourself to talk about what's going on in outer space and having the first one who makes an argument using tongue be the winner. You could use consistency that way. You still have no idea what you're talking about, right? And similarly with Bapal, you could have some kind of system of making sure that you didn't actually get contradictions, but it would still be true. There's some sense in which you've just no idea what's going on here. What are you talking about? Yeah. So the reason, this is really, this is a, how should I say, this is an artificial case, right? But I will suggest next time, I'll try to bring out, the thing about which shows that it's really quite general. What I mean is it connects to perfectly serious real world problems about how language is used. I mean, which is a good case that, there are plenty of words that people would like to just ban from the language. Yeah, I mean, plenty of words that good hearted liberals would just like to see out of the language. And it's a good question. How can, how can a word in itself be objectionable? I mean, if I say, if you say to someone, you're very ugly or you're very rude, then that might be very disagreeable, right? But the word itself is perfectly okay. You see what I mean? You can see objectionable thing as using words, even though the words themselves are perfectly all right. But in the case of words like which, and I don't really want to give a whole litany, but just because, you know, it is so hot button, right? People really take these words very seriously, very passionately. And well, just to give one example, I was in South Africa shortly after Mandela was elected, and I remember talking to someone on a commission for renaming every single place in South Africa, because so many of the names were objectionable. And she said to me at one point, she said, well, we think we finally got kafir out of every single place name in South Africa, right? I mean, the word itself is objectionable. It's not that you're a perfectly all right word and you're saying something disagreeable using it. It's that the word itself shouldn't be there. You want to expunge the word. And similarly for which there, the word itself can do damage. And with tonk, what you got is a very pure case where the word itself can be doing damage. You were all right until you let the word into your vocabulary. The minute you let tonk into your vocabulary is very powerful. You can now make all these inferences you couldn't have made otherwise. So you've got to have some way of criticizing and correcting here. This is a very, like I say, it's a very pure kind of sterile laboratory example. But it seems to me that the trouble here comes just because we don't have a truth table for tonk. I want to suggest a very simple diagnosis of what's going wrong in Wittgenstein. Wittgenstein's got a very good point. His point is you can't derive the rules for logical constants from the truth tables, right? That's the thing about in general. The bid in the middle can't explain what keeps us together. So this is very simple for what I'm saying here. But I think this is really, this is what's wrong with a whole of Wittgenstein's rule following discussion. The right part is this. You can't derive the rules from knowledge of the semantic value. Nonetheless, it might well be that we need there to be such a thing as knowledge of the semantic value because knowledge of the semantic value is what gives us knowledge of our objective in using words, sentences, in the ways we do. That's what one of the questions we're saying about. You've got to have some conception of what you're doing. It's natural to put it by saying you've got to have some definition. But it's not really a definition you need because not every word can be defined. You've got to know what it stands for with battle. You want to know which thing you're talking about. And if you've got a sign like tonk, you need to know what you're saying using the sign. So maybe what we need a truth table for is to make the practice intelligible. You could accept the negative thing Wittgenstein says about you can't derive every other aspect of your use of the sign from the truth table, but it may be nonetheless that unless you've got a reference for a name, unless you've got a map from objects of truth values for a predicate, unless you've got a truth table for a connective, you have no idea what you're about in using the sign. And if you think of it like that, the basic problem with tonk is just you can't write a truth table for it. It's not really the things go wild using tonk because you could try and contain the wildness and still something would be wrong. I know not everyone here has done logic, but can you think your hand up if this doesn't quite make sense? It does not quite make sense. Can you put your hand up if you're perfectly happy with the truth tables for and and or? Everyone? Some of you put up a very small hand. Okay, so you see... I hope I don't make too much of a mess of this. These two columns, you could have every permutation of truth and falsity for A and B. They're both true, one's true, one's false, one's false, one's true, they're both false. And then in the third column, you say, well, the truth values are the whole thing for each permutation of truth and falsity for A and B. So for A and B to be true, you need A and B to be both true, otherwise it's false. For A or B to be true, you just need one of the other to be true. It's only false if they're both false, right? So how does it go for tonk? If you get A and you get B, then you can infer A, tonk, B. And from A tonk, B, you can infer A, and you can infer B, right? That's all right. So how does it go then? So if A tonk, B is true, then A and B must both be true. And if both A and B are true, then A tonk, B is true. So that top line there is all right, right? But how does it go if... Well, let's do the bottom line too. So A tonk, B... If you get A false and B false, then A is false and B is false. So A tonk, B... Well, in order to infer A tonk, B, you need to have either A or B. So if they're both false, you don't have either of them. You can't infer A tonk, B. And if you don't have A tonk, B, you can't infer A and you can't infer B. So that's all right. Maybe if they're both false, so the whole thing is false, right? So the last line is all right. But if A is true and B is false, is A tonk, B true or false? Well, that must be true, right? Because if you get A, then you can infer A tonk, B. Right? So A tonk, B must be true. Yeah, that's all right. But then again, if you get A tonk, B, you can infer both A and B. So if you get A tonk, B, then A must be true and B must be true. But B is not true. B is false. Aha. So if you get A tonk, B, then A must be true and B must be true. So if you get A true and B false, then A tonk, B must be false, right? So if you get A true and B false, then A tonk, B must be false. That's all right? Because if you get A tonk, B, then you can infer both A and B. So if B is false, then A tonk, B must be false, right? But if you get A true and B false, then you get A. And from A you can infer at A tone B. So A, B, A tone B must be true. I mean false, right? Okay, so you can't really put anything in there. Yeah, you can't put in a true and you can't put in a false. You get the wrong answer either way. Yeah? And similarly, well, do I need to work it through if A is false and B is true? Yeah? It must be true because you've got one or the other and you've got the whole thing. But it must be false because you've got the whole thing and you've got both of these. So you can't write a truth table for A tone B. There's no such thing as the truth table for A tone B. That gives you a way of saying what's wrong with it. You can't fill it in as true here both times. You can't fill it in as false both times. There's nothing you can fill in. So if you think of it like that, you could think of what's going on here. You could say, well, it's not that you need the truth table to derive the rules of use for the sign. If you're just given the truth tables and told, well, get on with it, then you couldn't do that. You couldn't derive your use of the sign. The truth table can't be what keeps us together and so on. But it may be that nonetheless when you're going to use a sign like and or or or tongue, it doesn't make sense unless you have a truth table for it. So the pattern of use could be fundamental and there is not derived from anything else. But you still only have a legitimate pattern of use when you know the semantic value of the term. The semantic value could be like a regulator controlling which patterns of use are legitimate and which patterns of use are not legitimate. So with Baple, you could say, well, what's wrong with that? The fundamental thing that's wrong with that is you have no idea what the semantic value of Baple is. What does it stand for? Does it stand for the banana? Does it stand for the apple? You can't say either. So you always have to have some reference for a name, some map from obituary truth values for a predicate, some truth table for a propositional constant. That's always got to be there even though Wittgenstein was right, that the pattern of use is not derived from that thing. So what I'm suggesting is this is quite simple but I'll try and bring out next time how far reaching this is that there is really a kind of element, well, I have a sense of thunder and lightning playing about me as I say this, there is really a kind of elementary error in the conclusions Wittgenstein draws from the remarks on rule following that the really deep insight is that you can't derive the pattern of use from knowledge of the semantic value. The mistake is to say therefore we just throw out the notion of semantic value because it may be that we always need the semantic value to make intelligible to us what we're doing with a sign. So it isn't right to say there's only the use. We always have some insight into why we're using words the way we do. If you say why do you use and the way you do, it's because you've got the rules of inference. I don't know how you guys were taught basic logic. I spent the best years of my life drilling people in elementary logic and the way we used to do it back then was you just teach people the rules of inference. So these would be people who had just come straight from high school and before they had the chance to realize they weren't at high school anymore and they had an option as to what they did. We would just do it into them for three or four weeks what the rules of inference for logical constants were and we said don't bother about what it means, just learn this and then once they'd learned the rules of inference for logical constants two or three weeks in they would get the truth tables and the idea was, well at that point you suddenly understand what's going on here you understand why, if then has the rules of inference it does why or has the rule of inference that it does because you now see that this is the truth table and these rules are letting you preserve truth or falsity now it all falls into place I mean that was a theory anyway I mean many of my students spent the whole term in a complete focus to what was going on but the idea is that you understand why if you just get explained to you this is the rule for or then if you just told us what the rule for or then okay you can learn it but to understand why that's the rule for or you really need to know the truth table for or so that truth tables have this role to play for us in explaining and making it intelligible what we are doing with the sign we do not simply use signs like zombies we have some insight into what is going on and that I think is what's right about that thing about we use our experience of the world that we don't just have rules like that rule for BAPL we get the input from one object and the output relates to another object we use our experience to tell us what it is that we're referring to what we are talking about so that the fact that we use the signs the way we do is something that we have some insight into why it's going like that so we could acknowledge Wittgenstein's point that use is more fundamental than knowledge of truth conditions but keep a role for truth conditions and making use intelligible we could still say you only have a comprehensible use of a sign when it has some semantic value the idea was we're going to explain the truth conditions of sentences in terms of the references of the parts and that knowledge of truth conditions derived from knowledge of reference getting us with our knowledge of what we're about in our use of language so that we're not simply using language as well-drilled zombies but we have insight into what is going on so maybe the stuff that we did in the first nine weeks of the class did have a point after all and on that hopeful note we'll back it up for today carry on a little bit with prior's thing for next time