1 00:00:00,600 --> 00:00:02,340 Okay. Now we're on week two, 2 00:00:02,340 --> 00:00:09,180 and this week we're going to look at different types of arguments and in particular we're going to look at deduction and induction. 3 00:00:09,180 --> 00:00:15,610 These are two basic types of argument, and we'll be looking at different examples of each type. 4 00:00:15,610 --> 00:00:20,770 Welcome back, everyone. So it didn't put you off entirely last weekend? Difficult though it was. 5 00:00:20,770 --> 00:00:27,550 I'm sure it was difficult. Let's do a quick recap of last week so we can remember where we were. 6 00:00:27,550 --> 00:00:34,420 If you remember, I said that arguments are sets of sentences such that one of them, the conclusion, if you remember, 7 00:00:34,420 --> 00:00:42,910 is being said to be true and the others called the premises are being offered as reasons for believing the truth of the one. 8 00:00:42,910 --> 00:00:48,270 Or reasons for believing the one. Okay, so that's what an argument is. 9 00:00:48,270 --> 00:00:52,300 And I said it was important to distinguish arguments from two things. 10 00:00:52,300 --> 00:01:00,700 Firstly, sets of sentences that aren't arguments. And if you remember, I gave the two sorts of sets of sentences that are not arguments. 11 00:01:00,700 --> 00:01:07,570 Can anyone remember what they are? No assertion isn't an argument. 12 00:01:07,570 --> 00:01:12,130 An assertion is the second thing from which you should distinguish arguments. 13 00:01:12,130 --> 00:01:16,390 So I said that there are two sets. I think you misunderstood my question slightly. 14 00:01:16,390 --> 00:01:22,750 Whoever it was then. So there are two things from which you distinguish arguments. 15 00:01:22,750 --> 00:01:25,720 But the first one is sets of sentences. 16 00:01:25,720 --> 00:01:32,590 And I said that there are two things, two types of sets of sentence that you need to distinguish from an argument. 17 00:01:32,590 --> 00:01:38,290 Can anyone remember what those two types of sets of sentences were? 18 00:01:38,290 --> 00:01:45,340 Sorry. No. No. No. 19 00:01:45,340 --> 00:01:51,620 OK, maybe that's not a fair question. OK. The first one is sets of sentences that aren't related at all. 20 00:01:51,620 --> 00:01:55,360 Do you remember I talked about sea assault in Melbourne. Melbourne's in Australia. 21 00:01:55,360 --> 00:02:00,370 Well, until you are there in and a bit of context, that's not an argument, is it? 22 00:02:00,370 --> 00:02:08,830 It's just two unrelated sentences. And the second type of sets of sentence you should distinguish from arguments are those that are related, 23 00:02:08,830 --> 00:02:16,060 but not as an argument is related, not as the sets of sentences that constitute an argument are related. 24 00:02:16,060 --> 00:02:20,290 So in order for a set of sentences to be an argument, 25 00:02:20,290 --> 00:02:28,490 it's got to be related in the sense that the conclusion is being said to follow from the premises. 26 00:02:28,490 --> 00:02:38,320 OK. That's what an argument is, that one of the sets, one of the sentences of the set is being said to follow from the others. 27 00:02:38,320 --> 00:02:44,200 If it's if that relation isn't being said to be that, then it's not an argument. 28 00:02:44,200 --> 00:02:48,430 The second thing from which you must distinguish an argument is, is a sentence. 29 00:02:48,430 --> 00:03:01,560 And can anyone remember how you distinguish sentences from arguments or one way at least, in which you would distinguish a sentence from an argument? 30 00:03:01,560 --> 00:03:06,860 What do you mean by premise that a premise has a very particular definition? 31 00:03:06,860 --> 00:03:15,270 The definition is that a premise is a sentence that's being offered as reason for believing the truth of the conclusion. 32 00:03:15,270 --> 00:03:26,790 So what the questions is here is how do you distinguish a sentence or assertion from an argument? 33 00:03:26,790 --> 00:03:30,920 A sentence you could see is an incomplete argument, I suppose. 34 00:03:30,920 --> 00:03:39,620 But that's not what I was thinking of. Certainly there's no conclusion, nothing being. 35 00:03:39,620 --> 00:03:47,230 Well, there is something being postulated. If the sentence is being asserted, isn't the. 36 00:03:47,230 --> 00:03:55,250 There's no relation, that's right. But okay, look, let me hang on to this one more at Butler. 37 00:03:55,250 --> 00:03:58,700 So the skin. That's right. 38 00:03:58,700 --> 00:04:04,170 This is just a statement and a statement isn't an argument, is it? 39 00:04:04,170 --> 00:04:08,790 A statement isn't good or bad. Well, it could be, I suppose, couldn't it? 40 00:04:08,790 --> 00:04:13,770 A statement is true or false. And an argument is good or bad. 41 00:04:13,770 --> 00:04:23,040 Do you remember. Very important that, you know, you shouldn't call arguments true or false because arguments can't be true or false. 42 00:04:23,040 --> 00:04:28,610 The only thing that can be true or false is the sentences that make up the argument. 43 00:04:28,610 --> 00:04:38,850 What an argument is, is truth preserving. So if you have truth in the premises, then and it's a good argument, then the conclusion will be true. 44 00:04:38,850 --> 00:04:45,240 But notice, it's the premises that are true. And the conclusion that's true, not the argument itself. 45 00:04:45,240 --> 00:04:55,240 The most the argument can be is truth preserving. OK, so that's distinguishing arguments from sets of sentences and from sentences themselves. 46 00:04:55,240 --> 00:05:00,550 What we're going to do today is considered different types of argument. 47 00:05:00,550 --> 00:05:05,140 And we're going to start using some of the concepts that you've already mentioned this morning. 48 00:05:05,140 --> 00:05:11,800 So there are two basic types of argument. There are deductive arguments and they're inductive arguments. 49 00:05:11,800 --> 00:05:18,550 This is a very basic type of argument because you'll see later there are lots of other types of arguments in these categories. 50 00:05:18,550 --> 00:05:24,580 But these two categories are the most important. These are the ones you need to get a grip on. 51 00:05:24,580 --> 00:05:34,060 Okay, let's look at deductive arguments first. Now, these are such that the truth is their premises guarantees the truth of the conclusion. 52 00:05:34,060 --> 00:05:44,590 So if the premises are true, then the conclusion must be true, because if it's a good deductive argument, it's truth guarantying. 53 00:05:44,590 --> 00:05:47,860 So here's a deductive argument. You'll be familiar with this one. 54 00:05:47,860 --> 00:05:52,390 We used it last week. It's Friday. Marijan always wears jeans on a Friday. 55 00:05:52,390 --> 00:05:58,960 Therefore, Marianne is wearing jeans. Notice that the conclusion of this argument is it's true. 56 00:05:58,960 --> 00:06:05,230 But neither of the premises are. So that that should give you an idea that the argument is a good one. 57 00:06:05,230 --> 00:06:10,450 The conclusion is true, but actually neither of the premises are true. 58 00:06:10,450 --> 00:06:17,800 So this will be something we'll look at again when we look at what a good argument is next week relating to the real world. 59 00:06:17,800 --> 00:06:23,110 That's right. It's not Friday. Therefore, that premise is false. It's not true. 60 00:06:23,110 --> 00:06:28,840 You'll have to take it from me on the authority that I don't always wear jeans on Friday. 61 00:06:28,840 --> 00:06:30,820 I do happen to be wearing jeans today. 62 00:06:30,820 --> 00:06:36,370 But of course, that's irrelevant because it's neither Friday nor is it the case that I always wear jeans on a Friday. 63 00:06:36,370 --> 00:06:47,110 But what's important about this argument is that it's deductive, it's truth guaranteeing, at least conditionally upon the truth of the premises. 64 00:06:47,110 --> 00:06:51,520 Can you think of any situation? I really try and use your ingenuity here. 65 00:06:51,520 --> 00:06:55,450 Let's see if we get in which that would be true. Okay. 66 00:06:55,450 --> 00:07:00,280 It isn't true. We know that. But we're assuming for the sake of argument that it is true. 67 00:07:00,280 --> 00:07:06,100 So imagine a situation where that's true and that's true for some reason. 68 00:07:06,100 --> 00:07:12,340 I always wear jeans on a Friday. Could that be false? 69 00:07:12,340 --> 00:07:19,750 Can anyone think about the larger roster in the intervening week? 70 00:07:19,750 --> 00:07:27,670 Well. Well, that would that wouldn't that make that not true? 71 00:07:27,670 --> 00:07:33,110 Well, no. 72 00:07:33,110 --> 00:07:37,080 No, it doesn't. I mean. I hate wearing jeans. That may be nothing to do with it. 73 00:07:37,080 --> 00:07:43,440 I may wear jeans as a penance on a Friday because I once did something really ghastly and said to myself, right. 74 00:07:43,440 --> 00:07:49,740 Okay, from now on, I'm always going to wear jeans on Fridays. So it doesn't say that I want to. 75 00:07:49,740 --> 00:08:01,820 Can even think of it as a counterexample. OK, so it's true, it would be Friday on that day, but would this be true? 76 00:08:01,820 --> 00:08:06,470 No, it wouldn't, would it? So we've given what we've given there is a falsification of that. 77 00:08:06,470 --> 00:08:11,420 Not a counterexample to the argument. Okay. 78 00:08:11,420 --> 00:08:17,120 Do you see where I'm getting at? What we're doing is we're distinguishing the truth of the premises from the truth. 79 00:08:17,120 --> 00:08:26,810 Preserving this of the argument. Lots of us can think of situations where that's false or whether that's false. 80 00:08:26,810 --> 00:08:35,060 But that's not what I'm asking you to do. What I'm asking you to do is to think of a situation where that's true and that's true. 81 00:08:35,060 --> 00:08:42,030 And that's false. It is, isn't it? 82 00:08:42,030 --> 00:08:58,590 Yeah, well well, on a couple of other examples. Let's try one. So I'm on the moon or something like that. 83 00:08:58,590 --> 00:09:06,000 Very ingenious. I think what we do, what we're talking about is a situation where all these are. 84 00:09:06,000 --> 00:09:17,330 So these two are true together. Do you see what I mean and what you're giving me is one where it's not Friday. 85 00:09:17,330 --> 00:09:29,690 On to really what you're trying to make it not Friday, somehow by shifting me out of its time zone in which it is Friday, no, it won't do. 86 00:09:29,690 --> 00:09:34,010 But we do not need to guarantee it because all we're doing we're saying this is true. 87 00:09:34,010 --> 00:09:38,990 If this is true and if this is true, we're not saying this is true. 88 00:09:38,990 --> 00:09:43,440 I mean, this is another very important distinction when you're doing logic. 89 00:09:43,440 --> 00:09:48,040 You're you're not talking about the actual truth value of a sentence. 90 00:09:48,040 --> 00:09:52,480 Okay. So the truth value of that could be either true or false. 91 00:09:52,480 --> 00:09:58,750 You see what I mean? So that's the value of its truth. It's either true or false. 92 00:09:58,750 --> 00:10:09,810 And we're not saying it is true, but we're saying if it's true and if this is true, this can't be false. 93 00:10:09,810 --> 00:10:14,820 And as you rightly said, actually, if these two are true, it's impossible for this to be false. 94 00:10:14,820 --> 00:10:23,670 It really is, isn't it? Well, if we're looking at an argument, we're saying we're asking ourselves two questions. 95 00:10:23,670 --> 00:10:28,600 The questions are, does the conclusion follow from the premises? 96 00:10:28,600 --> 00:10:35,970 And in asking, that's what we're asking is if the premises were true, would the conclusion be true? 97 00:10:35,970 --> 00:10:39,300 If the premises are true? Would the conclusion be true? 98 00:10:39,300 --> 00:10:46,080 And if we look at these two premises and we ask that question, we're not asking whether the premises are true. 99 00:10:46,080 --> 00:10:52,380 We're saying if they're true. Would the conclusion be true? And the answer is yes. 100 00:10:52,380 --> 00:10:57,210 Can everyone see that this is a deductively valid argument? 101 00:10:57,210 --> 00:11:07,290 It's truth preserving. And therefore, it's very, very useful because we know that if the premises are true, the conclusion must be true. 102 00:11:07,290 --> 00:11:12,810 Now, in this particular case, this is not very useful because it's all hypothetical. 103 00:11:12,810 --> 00:11:23,820 But can you imagine if if this was something that we didn't know but we were wanting to test, then we could say, okay. 104 00:11:23,820 --> 00:11:27,930 It's Friday. Mariane always wears jeans on a Friday. Therefore, Marianne is wearing jeans. 105 00:11:27,930 --> 00:11:36,180 Then if you see that, I'm not wearing jeans. What do you know? 106 00:11:36,180 --> 00:11:42,870 One or other of these isn't true. Exactly. So if you see that Marianne isn't wearing jeans, 107 00:11:42,870 --> 00:11:50,220 you know either that it's not Friday that that one's false or that Marianne always wears jeans on a Friday is itself false. 108 00:11:50,220 --> 00:11:58,600 So, you know, either your hypothesis is false or your observation is false or. 109 00:11:58,600 --> 00:12:01,620 Oh, sorry. Well, you're quite right. Or both. That's right. 110 00:12:01,620 --> 00:12:11,850 So if you have a valid argument to deductively valid argument, the conclusion to which is false, you know that one of the premises must be false. 111 00:12:11,850 --> 00:12:21,390 And that's why truth preserving this is useful. Whatever the situation is, even if it turns out that the conclusions false anyway. 112 00:12:21,390 --> 00:12:24,030 Again, that's something we'll talk about more next week. 113 00:12:24,030 --> 00:12:30,210 The only thing that's important for now is that you understand what a deductively valid argument is. 114 00:12:30,210 --> 00:12:37,210 You understand that it's truth preserving that if the premises are true, the conclusion must be true. 115 00:12:37,210 --> 00:12:41,880 Okay, everyone happy with that? Let's move on. Okay. 116 00:12:41,880 --> 00:12:45,960 You should note, incidentally, that deduction is an either or thing. 117 00:12:45,960 --> 00:12:50,940 Either an argument is deductive or deductively valid or it's not. 118 00:12:50,940 --> 00:12:54,270 OK. There's no in between there. It's one or the other. 119 00:12:54,270 --> 00:13:03,420 A good deductive argument gives us conditional certainty, certainty conditional upon the truth of the premises. 120 00:13:03,420 --> 00:13:09,120 Well done. I can feel you getting it now. Okay. A bad one tells us nothing. 121 00:13:09,120 --> 00:13:16,600 Because if the argument isn't a good one, if it isn't truth preserving, then the conclusion could be either true or false. 122 00:13:16,600 --> 00:13:20,370 And we really don't know. Okay, so that's deduction. 123 00:13:20,370 --> 00:13:29,580 Let's move to inductive induction, inductive arguments as such that the truth of their premises makes the conclusion either more or less probable. 124 00:13:29,580 --> 00:13:34,590 Okay. It doesn't give us certainty. Makes the conclusion more or less probable. 125 00:13:34,590 --> 00:13:39,740 Now this means that inductive arguments can be either weak or strong. 126 00:13:39,740 --> 00:13:46,290 Okay. So here's an example of a strong inductive argument. 127 00:13:46,290 --> 00:13:52,760 The sun has risen, risen every day in the history of the universe. Therefore, the sun will rise tomorrow. 128 00:13:52,760 --> 00:14:03,510 Okay, that's a strong inductive argument. Why isn't that a deductive argument? 129 00:14:03,510 --> 00:14:09,210 So what may not be true, because arguments can't be true, of course, can they? 130 00:14:09,210 --> 00:14:16,920 This may not be true. OK. But but we're saying if this is true, then this will be true. 131 00:14:16,920 --> 00:14:29,820 So why is that? Not deductively certain. OK, so this could be true. 132 00:14:29,820 --> 00:14:34,990 And yet this false. And yet this is a good argument. 133 00:14:34,990 --> 00:14:43,720 Yes. Good. Well done. And that's exactly right. That's the hallmark of a strong inductive argument is even though you've got a very strong argument. 134 00:14:43,720 --> 00:14:50,120 I mean, if the sun has risen every single day in the history of the universe so far, I have no idea how they'll build the universities. 135 00:14:50,120 --> 00:14:54,820 But some. It's a it's old, right? 136 00:14:54,820 --> 00:15:01,930 If the sun has risen every day in the history of the universe, then it's hugely likely that the sun is going to rise tomorrow. 137 00:15:01,930 --> 00:15:13,210 Isn't it? And then you say, but we can't be 100 percent certain because who knows, the some may explode tomorrow, 138 00:15:13,210 --> 00:15:20,680 or maybe the law that ensures that the sun rises every morning and she has a bit of a dogleg in it. 139 00:15:20,680 --> 00:15:30,130 So it's saying, OK, what the law is, is every morning the sun will rise, except on the 7th of October, 2009. 140 00:15:30,130 --> 00:15:35,670 It's suddenly going to miss a day. And from then on, it's only going to rise every other day. 141 00:15:35,670 --> 00:15:46,650 Okay. For the rest of the history of time. Do we know that that isn't what the lawyers. 142 00:15:46,650 --> 00:15:54,360 Do we know that the son that the law that ensures that the sun has risen every morning in the history of the universe so far, 143 00:15:54,360 --> 00:16:00,500 won't tomorrow miss a day that. 144 00:16:00,500 --> 00:16:11,320 We don't have other shows. Well, it makes it weaker, but it means that we haven't got certainty. 145 00:16:11,320 --> 00:16:16,720 This could be true and this false. But it's a different type of argument. 146 00:16:16,720 --> 00:16:22,150 You mustn't think that because deductive arguments are certain, an inductive arguments aren't, that therefore, 147 00:16:22,150 --> 00:16:28,960 inductive arguments are somehow inferior because actually they're dealing with different things. 148 00:16:28,960 --> 00:16:32,920 This is the sort of argument that science deals with, isn't it? 149 00:16:32,920 --> 00:16:38,500 You observe that nature has been like this all the times before and then you 150 00:16:38,500 --> 00:16:42,880 extrapolate into the future to assume it's going to be like that in the future. 151 00:16:42,880 --> 00:16:47,440 So every daffodil you've ever seen in your life so far has been yellow. 152 00:16:47,440 --> 00:16:54,280 You're going to assume that the next daffodil you see will be yellow. There's another bad example, you see, but you see what I mean. 153 00:16:54,280 --> 00:17:08,740 I hope genes do just fine until are safe because there's a woops, sorry. 154 00:17:08,740 --> 00:17:13,950 I'm going the wrong way. This is the argument, right? 155 00:17:13,950 --> 00:17:18,840 An argument is a set of sentences. There are three sentences in this argument. 156 00:17:18,840 --> 00:17:27,870 The argument claim that's being made by this sentence is that if this is true and this is true, then this will be true. 157 00:17:27,870 --> 00:17:35,080 This will be true. OK. And this one. 158 00:17:35,080 --> 00:17:41,370 The inductive argument is saying, if this is true, this will be true. 159 00:17:41,370 --> 00:17:47,250 OK, now, in this case, we can say, but there could be a counterexample to this. 160 00:17:47,250 --> 00:17:53,760 The counter example might be that the sun explodes tomorrow or that the law of nature has 161 00:17:53,760 --> 00:17:59,090 had written into it from the history of time that it'll change tomorrow of all days. 162 00:17:59,090 --> 00:18:07,360 And we know that this doesn't give a certainty, but it gives us a jolly good reason for thinking that this is true, doesn't it? 163 00:18:07,360 --> 00:18:11,830 I mean, I could give you an inductive document that goes like this, in fact, let me give you one. 164 00:18:11,830 --> 00:18:17,780 Every time I've seen Marianne, she's been wearing earrings. Therefore, next time I see Marianne. 165 00:18:17,780 --> 00:18:22,120 She'll be wearing earrings. OK, now, juice. 166 00:18:22,120 --> 00:18:26,830 Is that a strong inductive argument? No. 167 00:18:26,830 --> 00:18:31,730 Well. It's not very strong, is it? I mean, the next time you see me, 168 00:18:31,730 --> 00:18:37,670 you might have come knocking on my door at seven o'clock in the morning and I've just got up and I don't wear earrings in bed. 169 00:18:37,670 --> 00:18:41,840 So the next thing you know, we know too much about the world, about people, 170 00:18:41,840 --> 00:18:50,510 about earrings and things like that to know that that's good inductive argument. 171 00:18:50,510 --> 00:18:59,050 Well, let's go back to this one and notice that here we're arguing from this not to it. 172 00:18:59,050 --> 00:19:03,920 Okay. This is a premiss, an argument, not a conclusion. OK. 173 00:19:03,920 --> 00:19:17,870 Whereas if we're looking here. Now I'm going to run with the other way. 174 00:19:17,870 --> 00:19:23,810 No, actually, what I was just about to tell you, that isn't good work. How do we get to this? 175 00:19:23,810 --> 00:19:32,860 We've seen the sun rise every single day. We see lots of observations and therefore we naturally extrapolate to a generalisation like this. 176 00:19:32,860 --> 00:19:37,870 This is a different form of reasoning. This is inductive reasoning. 177 00:19:37,870 --> 00:19:44,290 And it's the same reasoning that causes us to say something like this. But in this case, the same reasoning isn't as strong. 178 00:19:44,290 --> 00:19:49,120 Here's another one who takes a lucky rabbit's foot into an exam. 179 00:19:49,120 --> 00:19:53,140 If they ever go into exam, who used to take your lucky racquet rabbit's foot into exam? 180 00:19:53,140 --> 00:19:56,770 Who has a lucky red jumper or something like that? 181 00:19:56,770 --> 00:20:03,340 We've all had the experience of something's really nice happening to us and we were wearing something or carrying something. 182 00:20:03,340 --> 00:20:05,950 And we think, you know, maybe I'll wear that again. 183 00:20:05,950 --> 00:20:12,890 I'll be lucky again because we extrapolate from what's happened in the past to what's going to happen in the future. 184 00:20:12,890 --> 00:20:19,340 I've lost you. I can see you. I can. I'm looking at your faces. New. Gone. Right. 185 00:20:19,340 --> 00:20:25,270 The only thing you need to remember is that a deductive argument. You've got certainty. 186 00:20:25,270 --> 00:20:29,140 Because if the premises are true, the conclusion must be true. 187 00:20:29,140 --> 00:20:34,610 In an inductive argument, you haven't got certainty, you've only got probability. 188 00:20:34,610 --> 00:20:39,940 Okay, this ARG, this premiss gives you probable reason to believe this. 189 00:20:39,940 --> 00:20:44,260 If this premise is true, this conclusion is probably true. 190 00:20:44,260 --> 00:20:51,790 Okay. But it's not certainly true. And if this premise is true, then this conclusion. 191 00:20:51,790 --> 00:20:56,920 It's not even probably true, isn't is it? This is a very weak inductive bargain. 192 00:20:56,920 --> 00:21:02,590 This this gives you some reason for believing this, but not very much. 193 00:21:02,590 --> 00:21:07,540 Have a look at these. Go through. I'm going to give you a couple of minutes to do them on your own. 194 00:21:07,540 --> 00:21:16,660 So you really try and work this out for yourself, decide which of those are deductive arguments and which of those are inductive arguments. 195 00:21:16,660 --> 00:21:20,110 And then we'll have a look at them together. So the sun is coming? 196 00:21:20,110 --> 00:21:23,920 Well, actually, let's do them together. I think that's probably easier at this point. 197 00:21:23,920 --> 00:21:30,570 Let's have a look at the sun is coming out. So the rain should stop soon, which is the conclusion of that. 198 00:21:30,570 --> 00:21:35,590 Okay. Well. Well, let's let's do the canonical way, shall we? 199 00:21:35,590 --> 00:21:41,410 Just so we've all got it, which is the conclusion of this argument. The rain should stop soon. 200 00:21:41,410 --> 00:21:48,820 That's what we're claiming. And the reason we're giving for that claim is the sun is coming out. 201 00:21:48,820 --> 00:21:55,090 So the the premises, the sun is coming out. Therefore, the rain should stop soon. 202 00:21:55,090 --> 00:22:00,580 Now, just the truth is that premiss make the the truth as a conclusion certain. 203 00:22:00,580 --> 00:22:08,020 No, you can't have more or less certain. Sorry. It's more or less probable, but not more or less certain. 204 00:22:08,020 --> 00:22:13,470 Okay. So this is inductive or deductive. Put up your hands if you think it's inductive. 205 00:22:13,470 --> 00:22:17,170 Yay! You see, I knew you got it. Really. Okay, good. 206 00:22:17,170 --> 00:22:20,590 That's the end deal. What about this one? Let's do it the canonical way. 207 00:22:20,590 --> 00:22:32,020 What's the conclusion? All right, I'm going to make you do the things that I make undergrad you used to make undergraduates to and notice those. 208 00:22:32,020 --> 00:22:37,990 Can you make that a proper sentence? John won't be at the party. 209 00:22:37,990 --> 00:22:51,760 That's right, it's obvious what the sentence should be, isn't it? So, OK, the conclusion is John won't be at the party and the premises are good. 210 00:22:51,760 --> 00:22:56,290 There are two parts to premises here. One is, Jane, is that the party? 211 00:22:56,290 --> 00:23:00,880 And the other is if Jane is at the party, John won't be at the party. 212 00:23:00,880 --> 00:23:07,930 Notice that that's a complex sentence that's constituted of two sub two sentences within the sentence. 213 00:23:07,930 --> 00:23:14,320 But you don't separate those two to make them two different premises because the sentence being asserted as if, 214 00:23:14,320 --> 00:23:18,070 Jane, is that the party, John, won't be. That's the premise. Good. 215 00:23:18,070 --> 00:23:22,450 Okay. So we've got an argument that goes if Jane is that the party, John, won't be at the party. 216 00:23:22,450 --> 00:23:27,820 Jane is at the party. Therefore, John won't be at the party. Is that deductive or inductive? 217 00:23:27,820 --> 00:23:33,900 Put up your hands if you think it's inductive. OK. 218 00:23:33,900 --> 00:23:37,680 Put up your hand, he's against deductive. Well done. 219 00:23:37,680 --> 00:23:42,390 OK. So you are getting this, OK? It's the science. The house is a mess. 220 00:23:42,390 --> 00:23:48,780 Therefore, Lucy must be at home. What's the conclusion? Just Lucy must be at home. 221 00:23:48,780 --> 00:23:53,640 The ZET therefore just marks the conclusion rather than being the conclusion. 222 00:23:53,640 --> 00:23:57,960 Okay. Lucy must be home premiss. The house is a mess. Inductive or deductive. 223 00:23:57,960 --> 00:24:02,090 Put up your hand if you think inductive. Well done. 224 00:24:02,090 --> 00:24:09,780 Can you give me a counterexample to that argument? Yes, that's right. 225 00:24:09,780 --> 00:24:13,450 Okay. So the house is a mess, but Lucy isn't at home. 226 00:24:13,450 --> 00:24:18,070 You've had burglars instead. Good. OK. I think he's in the bathroom or the bedroom. 227 00:24:18,070 --> 00:24:24,490 He's not in the bathroom, so he must be in the bedroom. Conclusion's obvious. 228 00:24:24,490 --> 00:24:29,230 It must be in the bedroom and the two premises, either using the bathroom or the bedroom. 229 00:24:29,230 --> 00:24:34,030 He is not in the bathroom. Okay. Deductive or inductive? 230 00:24:34,030 --> 00:24:38,170 Deductive. Well done. Okay. Dog would have bought it if it saw a stranger. 231 00:24:38,170 --> 00:24:42,880 It didn't bark, so it didn't see a stranger. Deductive. 232 00:24:42,880 --> 00:24:48,780 Good. No one in Paris understands me. So my French must be rotten or the Parisians are stupid. 233 00:24:48,780 --> 00:24:53,780 Sir, I got this from a book inductive. 234 00:24:53,780 --> 00:24:57,100 Okay. It's difficult that one, but it is inductive. You're quite right. 235 00:24:57,100 --> 00:25:04,080 Because what's the conclusion? That's right. 236 00:25:04,080 --> 00:25:08,440 It's actually a complex conclusion, isn't it. My French must be rotten. 237 00:25:08,440 --> 00:25:13,390 All the Parisians are stupid and they're on the premises. No one in Paris understands me. 238 00:25:13,390 --> 00:25:23,510 So it may be the case that if that's true. These are true, but but there are other reasons for nobody understanding me on that as well. 239 00:25:23,510 --> 00:25:29,870 OK, good. So you have actually got it. Even if we got tied up in a few knots there. 240 00:25:29,870 --> 00:25:38,080 No. Not in sale to right. Logicians studied deduction by studying valid argument forms. 241 00:25:38,080 --> 00:25:42,940 Now it's very important to distinguish form from content. 242 00:25:42,940 --> 00:25:49,820 Okay. Arguments are deductively valid in virtue of their forms rather than their contents. 243 00:25:49,820 --> 00:25:53,990 Now, that's not true of all deduction, but it's true of most deduction. 244 00:25:53,990 --> 00:25:59,570 So let's have a look. What I mean here, all men are mortal, Socrates and man. 245 00:25:59,570 --> 00:26:06,440 Therefore, Socrates is mortal. Okay. All actions that produced the greatest happiness to the greatest number. 246 00:26:06,440 --> 00:26:10,550 I got very bored writing it out. So the greatest happiness is greatest number. 247 00:26:10,550 --> 00:26:14,660 All actions that produced the greatest happiness, the greatest number are right. Morally right. 248 00:26:14,660 --> 00:26:18,890 That is, that action produced the greatest happiness of the greatest number. 249 00:26:18,890 --> 00:26:27,310 Therefore, that action was right. Okay. Can you see that the form of those two arguments is exactly the same? 250 00:26:27,310 --> 00:26:32,230 Can you see that? So the content of the two arguments is quite different. 251 00:26:32,230 --> 00:26:39,670 This is an argument about Socrates and mortality. And this is an argument about morality and the greatest happiness of the greatest number. 252 00:26:39,670 --> 00:26:45,370 Completely different topics, completely different content. But each of the arguments has the same form. 253 00:26:45,370 --> 00:26:51,680 Can anyone try and write down the form? Tell me the form of that argument. 254 00:26:51,680 --> 00:26:58,630 This the structure of it. Do you not know what I mean? 255 00:26:58,630 --> 00:27:05,460 No. Okay, let's do it together. All A's are B. 256 00:27:05,460 --> 00:27:10,770 S isn't a, therefore, s is a B. Did you get that? 257 00:27:10,770 --> 00:27:15,510 All A's are B, so. Aye, aye. 258 00:27:15,510 --> 00:27:19,440 Let's stir an interpretation here. Aye. 259 00:27:19,440 --> 00:27:23,250 Equals. Let's do it properly here. 260 00:27:23,250 --> 00:27:30,930 X is a man. X is mortal. 261 00:27:30,930 --> 00:27:37,730 S is Socrates. And the form this is all A's. 262 00:27:37,730 --> 00:27:42,720 R. V. S is an A therefore. 263 00:27:42,720 --> 00:27:46,410 S is a b with me. Let me do it again. 264 00:27:46,410 --> 00:27:54,960 Can you see inside. So if this is the interpretation, this is I've just changed the words for symbols here. 265 00:27:54,960 --> 00:28:02,220 And the symbols are only letters. So a A of X says X is a man. 266 00:28:02,220 --> 00:28:08,790 X is mortal. Is B an s. Is Socrates. So all A's are B. 267 00:28:08,790 --> 00:28:13,530 S is an A. S is therefore. S is a B with me. 268 00:28:13,530 --> 00:28:23,320 So you can do that for the other argument. What would we have to say that A is there. 269 00:28:23,320 --> 00:28:32,550 Good X is A is an action, B, X is. 270 00:28:32,550 --> 00:28:37,000 Gone. Produce. 271 00:28:37,000 --> 00:28:41,300 No. Okay. All men are mortal. 272 00:28:41,300 --> 00:28:44,760 All actions that produce the grace of disgrace. 273 00:28:44,760 --> 00:28:52,060 No. All right. Okay. So actually, a isn't actions is is its actions. 274 00:28:52,060 --> 00:28:56,530 That produced the no not right actions, actions that produced the greatest happiness, great number. 275 00:28:56,530 --> 00:29:04,200 So all men are mortal and all actions that produces race, happiness, the greatest number. 276 00:29:04,200 --> 00:29:12,760 Right. You with me. So all A's or men are B's mortal. 277 00:29:12,760 --> 00:29:16,600 All A's actions are of gross happiness. Gross. No. 278 00:29:16,600 --> 00:29:24,630 All right. OK. And then the next one, that action produced the greatest happiness, the greatest number. 279 00:29:24,630 --> 00:29:31,640 You've got Socrates here is a particular thing, justice. That action is a particular thing. 280 00:29:31,640 --> 00:29:41,020 Okay. And you're saying that particular thing is a man, i.e., falls into this class here. 281 00:29:41,020 --> 00:29:45,340 And therefore, he falls into the other class, too. OK. 282 00:29:45,340 --> 00:29:50,320 So both those arguments have the form. All A's a B. 283 00:29:50,320 --> 00:29:58,930 S isn't they therefore. S is a b. Now, the point of this is just to get you to distinguish form and content. 284 00:29:58,930 --> 00:30:04,480 Can you see that an argument can have different forms. And yet the same content. 285 00:30:04,480 --> 00:30:11,590 Sorry, different contents. And yet the same form. OK. So these are two arguments of exactly the same form, different contents. 286 00:30:11,590 --> 00:30:22,030 What's important about this is that logic is topic neutral. Once you've learnt how to do logic, it doesn't matter what you're doing it with or on. 287 00:30:22,030 --> 00:30:28,660 It's always the same. Logic is the same. Whether you're talking about the colour of chairs, whether you're talking about biochemistry, 288 00:30:28,660 --> 00:30:33,190 whether you're talking about the philosophy of time, doesn't matter what you're talking about. 289 00:30:33,190 --> 00:30:40,180 If an argument is valid, it'll be valid by virtue, its form, whatever the topic is you're talking about. 290 00:30:40,180 --> 00:30:48,640 So logic is the ultimate transferable skill. If you've learnt logic, you can do it with whatever you happen to be talking about, 291 00:30:48,640 --> 00:30:55,950 whatever it is you're interested in, whether it's art history or fashion. 292 00:30:55,950 --> 00:31:00,640 Right. OK. Let's have a look at a few argument forms. 293 00:31:00,640 --> 00:31:09,980 Here's a valid argument form. If P, then Q, p, therefore Q. 294 00:31:09,980 --> 00:31:15,230 What's pee standing in for here? What type of thing is it standing in for? 295 00:31:15,230 --> 00:31:19,520 Can anyone tell me a good or a sentence? 296 00:31:19,520 --> 00:31:25,190 I was going to say, but the premise is even better. Yes. Well done. So this is one sentence. 297 00:31:25,190 --> 00:31:32,020 What's this? No. 298 00:31:32,020 --> 00:31:37,310 No, not even that it's. Oh, actually, I am. That's a premise. 299 00:31:37,310 --> 00:31:44,850 Actually, that's a premise. That's only a sentence. Can you see why? 300 00:31:44,850 --> 00:31:53,580 That's right. Okay, so if P, then Q is one premiss, P is the other premiss and Q is the conclusion. 301 00:31:53,580 --> 00:32:01,140 So all we've done there, instead of thinking about actual sentences, we've just put in what are called sentence letters, any letter will do. 302 00:32:01,140 --> 00:32:04,740 Doesn't matter, just so long as you get the form of the argument. Right. 303 00:32:04,740 --> 00:32:09,840 Can you think of an argument that fits that form. OK. 304 00:32:09,840 --> 00:32:14,010 Just think for yourself now of an argument that fits that form. 305 00:32:14,010 --> 00:32:20,400 You could use one that we've already used. You could use one to do with the colours of the chair in this room. 306 00:32:20,400 --> 00:32:27,140 Quite difficult, but say, if you can think of one, try. If I'm happy, then I see. 307 00:32:27,140 --> 00:32:33,010 I am happy, therefore I will see. Give her a clap. 308 00:32:33,010 --> 00:32:45,040 Well done. That's exactly right. Can anyone think of another one? No, there's no all there. 309 00:32:45,040 --> 00:32:51,210 No. Just the impossible. Cannot on. 310 00:32:51,210 --> 00:33:00,190 If the impossible cannot happen, then. No, you're not quite getting the idea. 311 00:33:00,190 --> 00:33:06,010 Now, this will be happening to lots of you. This is not just just you. The form is if sentence. 312 00:33:06,010 --> 00:33:11,200 Then sentence. Sentence. Therefore, sentence. 313 00:33:11,200 --> 00:33:15,070 And these two have got to be the same sentence. And these two have got to be the same sentence. 314 00:33:15,070 --> 00:33:20,980 So the form of this has got to be if P, then Q P, therefore. 315 00:33:20,980 --> 00:33:26,200 Q Think of another one thing. You think to yourselves first and then then when you feel confident that you've got it. 316 00:33:26,200 --> 00:33:32,020 Put your hands up and we'll try. This is really doing logic. 317 00:33:32,020 --> 00:33:35,350 So did he. If you find it odd. That's right. 318 00:33:35,350 --> 00:33:52,060 It's in the nature of the beast. Are you? 319 00:33:52,060 --> 00:33:58,420 Well, sit down and think for yourself and then try again. No, you've just said you didn't notice. 320 00:33:58,420 --> 00:34:11,590 Okay. Go on, Nusaybin. No, that was an if P and Q, wasn't it? 321 00:34:11,590 --> 00:34:21,970 And we're looking for an if P, then. Q These words that are left are the logical words and it's getting the logical words right. 322 00:34:21,970 --> 00:34:26,800 If then and or not, that's hugely important. 323 00:34:26,800 --> 00:34:36,380 Have you got one. Goes, okay. 324 00:34:36,380 --> 00:34:40,120 If he gets a bus, then he's ecofriendly. He does get a bus. 325 00:34:40,120 --> 00:34:47,190 Therefore, he's ecofriendly. Good. Well done, Paul. If it rains, I raised an number of. 326 00:34:47,190 --> 00:34:52,990 My umbrella is up. Therefore, it is rain. Oh. Something wrong with that? 327 00:34:52,990 --> 00:34:57,520 What was wrong with it? Now that the sentences were great? 328 00:34:57,520 --> 00:35:02,890 Say it again, though. OK. 329 00:35:02,890 --> 00:35:06,370 OK. So Piers, it is raining. OK, and Q is. 330 00:35:06,370 --> 00:35:14,480 I raised an umbrella. He now was p my umbrella is up. 331 00:35:14,480 --> 00:35:20,870 What was P? It's raining. So what do you need there instead. 332 00:35:20,870 --> 00:35:25,130 It is raining then for your brother. Do you see what you were doing? 333 00:35:25,130 --> 00:35:32,510 Those you are committing the fallacy of affirming the consequent very common fallacy. 334 00:35:32,510 --> 00:35:36,710 Well, do phalluses next week. I think so. But you say it has to be. 335 00:35:36,710 --> 00:35:39,500 You have to have the letters in the right order. 336 00:35:39,500 --> 00:35:48,680 Because what you gave me initially wasn't a valid argument, but a valid argument could easily be made from it just by transposing those. 337 00:35:48,680 --> 00:35:55,970 Do you have another? If it's sunny, then I'll take my dog for a walk. 338 00:35:55,970 --> 00:35:59,810 It's sunny, so therefore I'll take my alterable. 339 00:35:59,810 --> 00:36:10,910 Exactly, so, Piers, it is sunny. Q is I'm taking my dog for a walk and the argument is if it's sunny, then I'm taking my dog for a walk. 340 00:36:10,910 --> 00:36:15,160 It is sunny. Therefore, I'm taking my dog for a walk. 341 00:36:15,160 --> 00:36:20,360 Okay. Now, that has to be valid, doesn't it? Sorry, that has if those premises are true, 342 00:36:20,360 --> 00:36:28,580 that conclusion has to be true because any argument of this form must be a good argument is deductively valid. 343 00:36:28,580 --> 00:36:39,380 Everyone else wants to try another one. If the person strikes, then we will have no. 344 00:36:39,380 --> 00:36:43,850 Good. Okay. If the postman is striking, then we will have no letters. 345 00:36:43,850 --> 00:36:50,540 The postman are striking, therefore we'll have no letters. So P is. 346 00:36:50,540 --> 00:36:56,280 The postman's strike? No, not if because the if okay. The postman striking and Q is. 347 00:36:56,280 --> 00:37:01,140 We will have no letters. So if the postman is striking them, we'll have no letters. 348 00:37:01,140 --> 00:37:05,520 The postman are striking. Therefore we'll have no letters. Good. 349 00:37:05,520 --> 00:37:17,720 Okay. One more and then we'll move on. This is looking good. 350 00:37:17,720 --> 00:37:23,060 That's right. If he's breathing, then he's alive. He is breathing. Therefore, he's alive. 351 00:37:23,060 --> 00:37:26,690 Okay. Yeah, good. Okay. Dead easy, isn't it? 352 00:37:26,690 --> 00:37:34,590 Once you get the idea of it. And here's the story salesman. 353 00:37:34,590 --> 00:37:39,430 The third part of the dead parrot. 354 00:37:39,430 --> 00:37:44,920 Yes, I'm sure we could meet one there. Here we are. If there are no chance factors in chess than chess is a game of skill. 355 00:37:44,920 --> 00:37:48,760 There are no chance factors in chess. Therefore, chess is a game of skill. 356 00:37:48,760 --> 00:37:58,720 What what's P here? Go to what's queue. 357 00:37:58,720 --> 00:38:03,760 Good. Well done. Here's another argument. OK, that was modus pronouns. 358 00:38:03,760 --> 00:38:08,620 By the way. So you know how to do. No, no. Just pens his most toplines. 359 00:38:08,620 --> 00:38:16,600 The mode of denial. If P, then Q not Q, therefore not P. 360 00:38:16,600 --> 00:38:21,850 Okay. If P. Then Q not Q therefore not P. 361 00:38:21,850 --> 00:38:27,860 So this is saying in effect, that P is sufficient for Q. 362 00:38:27,860 --> 00:38:44,250 Sorry. Have I got it the wrong way round? 363 00:38:44,250 --> 00:38:53,460 Now, I have got right way round. It's what we're saying here is that CU is necessary for PE. 364 00:38:53,460 --> 00:38:57,550 And so if cue. Isn't the case then, P isn't the case? 365 00:38:57,550 --> 00:39:07,350 Well, let's have a look at the example and then you can come up with your own. Actually, this example is wrong because that shouldn't be in there. 366 00:39:07,350 --> 00:39:12,120 But let's let's do it. If the dog didn't know the visitor well, the dog would have barked. 367 00:39:12,120 --> 00:39:17,400 OK. The dog didn't bark. Therefore, the dog did know the visitor. 368 00:39:17,400 --> 00:39:21,870 That shouldn't be in there. That's the one that I was saying I'd got wrong before we started. 369 00:39:21,870 --> 00:39:31,740 So if you take that not out, I won't draw on the screen there. So on your handouts, make sure that you take that not out on slide 16. 370 00:39:31,740 --> 00:39:36,850 Write that down. I think it's 16. Yep. Because that's that's secret. 371 00:39:36,850 --> 00:39:44,720 But you do see how that argument is valid. If it's true that if the dog didn't know the visitor well, the dog would have baulked. 372 00:39:44,720 --> 00:39:48,250 It's a good guide dog got guard, dog, guard, dog. 373 00:39:48,250 --> 00:39:56,080 No, I don't. It didn't bark. Therefore, it must have known the visitor well, mustn't it? 374 00:39:56,080 --> 00:40:03,750 OK, so see if you can come up with something of that form now. 375 00:40:03,750 --> 00:40:11,940 I'll take the example out, so it's not confusing. Have you come up with an already. 376 00:40:11,940 --> 00:40:15,210 Well done. Fantastic. Absolutely right. 377 00:40:15,210 --> 00:40:24,120 So, Piers, I have money. Q Is I would be in the pub sat right. 378 00:40:24,120 --> 00:40:34,890 I'm not in the pub, therefore I have no money. If I had if I had money, so having money would be sufficient for you to be in the pub, OK? 379 00:40:34,890 --> 00:40:41,120 But you're not in the pub, therefore you haven't got any money. Okay, anyone else wants to have a go? 380 00:40:41,120 --> 00:40:50,170 Gentlemen, the sun is. Good. 381 00:40:50,170 --> 00:40:56,650 You've got it, I think. Does anyone else want to have a go? Or does everyone feel that they've got that? 382 00:40:56,650 --> 00:41:04,870 Was it. Sorry. Say it again. If the sun is out, I will take my dog for. 383 00:41:04,870 --> 00:41:10,360 OK, so here's the sun is out and Q is I'll take my dog for a walk. 384 00:41:10,360 --> 00:41:14,230 Oh, I'm sorry. Those of you who saw the error. 385 00:41:14,230 --> 00:41:21,540 That's quite right. Okay. What should be here? I'm not taking my dog out for a walk. 386 00:41:21,540 --> 00:41:25,830 Therefore, the sun is not out yet. 387 00:41:25,830 --> 00:41:41,060 That's right. Good. Okay, try one more than. We've got that as I got that wrong. 388 00:41:41,060 --> 00:41:44,870 Yes. OK. No, we are not in the wrong place there. 389 00:41:44,870 --> 00:41:55,180 Didn't we have? How did it go again? If I'm hungry, then I won't concentrate. 390 00:41:55,180 --> 00:42:08,430 I right. It would be I will write this one down, because there are knots in there that we need to get. 391 00:42:08,430 --> 00:42:17,730 Right. Because as you say. Okay, so P is. I am hungry. 392 00:42:17,730 --> 00:42:23,330 Q is. I can't concentrate. OK. 393 00:42:23,330 --> 00:42:29,690 Notice that we've changed Q. The Q is actually a negative here. 394 00:42:29,690 --> 00:42:33,830 That's where we're. It's very easy to get tied up. So be very careful of this. 395 00:42:33,830 --> 00:42:39,860 Negatives immediately make things quite difficult. So but Nipon, we can do it. 396 00:42:39,860 --> 00:42:51,950 Okay. So. Q is I can't concentrate now not. Q Therefore is I can concentrate therefore I'm not hungry. 397 00:42:51,950 --> 00:42:58,570 Are you, are you with me to see how that works? So you had the right sentences, you were just not using the negatives the right way. 398 00:42:58,570 --> 00:43:05,460 I've forgotten who and who said this. So I'm looking at all the wrong people. Okay, one more on this one, because it is quite difficult, Paul. 399 00:43:05,460 --> 00:43:17,050 Oh, actually, we had you, Paul. So do we have you for. Okay. 400 00:43:17,050 --> 00:43:29,020 Good. Okay. If I've if I catch my train, though, so I start again, if I missed my train, I'll be late. 401 00:43:29,020 --> 00:43:38,410 I'm not late. Therefore, I haven't missed my train. You don't have to use the same words as always. 402 00:43:38,410 --> 00:43:45,850 You. Now, this is this is actually the important point. You don't have to use the same words as almost the words have to say meaning. 403 00:43:45,850 --> 00:43:48,610 Or do you see what I mean? 404 00:43:48,610 --> 00:43:58,030 But it's a very when you're learning logic, it's a very good idea to use the same words because it cuts out one area of complication. 405 00:43:58,030 --> 00:44:05,310 Do you see that? It just you know, why it you why change your language when what it's going to do is confuse you, keep things as simple as possible. 406 00:44:05,310 --> 00:44:09,590 This is quite hard enough without adding layers of complication in. 407 00:44:09,590 --> 00:44:13,120 Okay. Good. You did that well. So what if I got a. 408 00:44:13,120 --> 00:44:23,950 We've already tried that. Good. Let's try another one. This is a disjunctive syllogism, P or Q, not P, therefore. 409 00:44:23,950 --> 00:44:48,730 Q Okay, have a go at that one. P or Q, not P, therefore Q. 410 00:44:48,730 --> 00:44:57,010 OK. Oh, good. Look at you, hands going up immediately now the reigning. 411 00:44:57,010 --> 00:45:01,990 Brilliant. OK. It's either raining or it's sunny. It's not raining. 412 00:45:01,990 --> 00:45:11,760 Therefore, it's sunny. Good. Well done. Battement. 413 00:45:11,760 --> 00:45:19,560 Good. Well done. Anyone else? Walking or driving, I'm not. 414 00:45:19,560 --> 00:45:24,120 Good. OK. I think you've got it, one side knows how. 415 00:45:24,120 --> 00:45:27,630 Good. Well done. OK, I've noticed that that works. 416 00:45:27,630 --> 00:45:41,460 If if you've got an exclusive or because all is actually an ambiguous word in English, it can mean either or it can mean not both. 417 00:45:41,460 --> 00:45:47,640 And if this was either, this has got to be either or hasn't it? 418 00:45:47,640 --> 00:45:52,320 If it were not both, you couldn't get the conclusion, could you? 419 00:45:52,320 --> 00:46:00,630 So that's where English can medium lead us astray a little bit because English is itself ambiguous. 420 00:46:00,630 --> 00:46:04,470 Okay, here's my example either. This is actually Bertrand Russell example. 421 00:46:04,470 --> 00:46:11,220 Either we hope for progress through improving morals or we hope for proof, progress from improving intellect, intelligence. 422 00:46:11,220 --> 00:46:17,250 We can't hope for progress through improving morals. Therefore, we must hope for progress through improving intelligence. 423 00:46:17,250 --> 00:46:24,930 What this should tell you instantly, we've been looking at very simple ones, but actually these forms can be very complicated. 424 00:46:24,930 --> 00:46:30,040 One of the things I'm going to ask you to do this week while you're at home is when you read your newspaper, 425 00:46:30,040 --> 00:46:35,310 you listen to your television or argue with your friends in the pub or whatever you happen to do. 426 00:46:35,310 --> 00:46:44,040 I want you to to try and identify arguments that come up whenever you hear the words, if then and or not. 427 00:46:44,040 --> 00:46:50,910 If and only if all these logical words. All is lovely, logical words. 428 00:46:50,910 --> 00:46:55,040 Just you've got to be sensitised to them this week because I want you to. 429 00:46:55,040 --> 00:47:01,290 Hey, you had to every time you hear this, then I want you identifying the form of the argument in which you find it. 430 00:47:01,290 --> 00:47:13,100 Course, it might not be in an argument might it might be just a free-standing assertion, but have a look, see if there is an argument there. 431 00:47:13,100 --> 00:47:19,010 Second, second sentence. Yes. 432 00:47:19,010 --> 00:47:24,950 Each of the premises is an asserted sentence, a sentence that's being asserted, isn't he? 433 00:47:24,950 --> 00:47:32,900 So Russell is saying, you know, it's true that either we hope for progress this way or we hope for it this way. 434 00:47:32,900 --> 00:47:37,610 Okay. There's no other option. We can't hope for it this way. 435 00:47:37,610 --> 00:47:42,460 He's asserting, therefore, we must hope for it that way. 436 00:47:42,460 --> 00:47:54,860 Okay. Well, I won't sing direct. 437 00:47:54,860 --> 00:48:03,800 Heigel, what's false here? So is it the first premise, let's start to use the language now? 438 00:48:03,800 --> 00:48:13,990 Is it the first premise that false or the second? Well, I'm pretty intelligence isn't a sentence on appears here and here. 439 00:48:13,990 --> 00:48:28,750 So what? So is that the false premise sold that one? 440 00:48:28,750 --> 00:48:31,850 Right. I think I'm going to put this on one side because, A, 441 00:48:31,850 --> 00:48:37,610 we're not really looking at the truth of the premises and B, you've got to take the premises as they are here. 442 00:48:37,610 --> 00:48:44,180 This is what's being asserted. So we're not saying this is true or that this is true. 443 00:48:44,180 --> 00:48:49,840 What we're saying is, if this is true and this is true, then this must be true. 444 00:48:49,840 --> 00:48:57,510 Okay. These conditionals are very important. Decision by presupposition. 445 00:48:57,510 --> 00:49:01,720 What? We'll get onto that later on. 446 00:49:01,720 --> 00:49:11,520 So what I want to get is not just sensitising us now to deduction and induction into the form of an argument that that's what we need to get today. 447 00:49:11,520 --> 00:49:15,750 Okay, let's move on. Here's another one, Liben. It's law. 448 00:49:15,750 --> 00:49:20,640 A is F, A equals B, therefore, B is F. 449 00:49:20,640 --> 00:49:24,930 I'll give you my example of that because it's quite difficult one. Jane is tall. 450 00:49:24,930 --> 00:49:31,070 Jane is the bank manager. Therefore, the bank manager is tall. 451 00:49:31,070 --> 00:49:36,980 If these are true. Is that true? Has to be, doesn't it, can't be anything else. 452 00:49:36,980 --> 00:49:42,350 Don't think of a couple of examples of that one. Go for it. 453 00:49:42,350 --> 00:49:47,460 Don't spark. No, I don't think it's going to work. 454 00:49:47,460 --> 00:49:52,590 Why is that not going to work? Let let's see. Why is this not going to work? 455 00:49:52,590 --> 00:49:57,370 Will dogs bark? Doesn't have the form. A is A is. 456 00:49:57,370 --> 00:50:05,040 F is. The chair is blue. Marianne is tall. The board duster is lost, etc. 457 00:50:05,040 --> 00:50:08,730 Not a dog. You could say the dog. 458 00:50:08,730 --> 00:50:17,580 The dog is barking but dogs bark is saying of one class of things that they fit another class of things. 459 00:50:17,580 --> 00:50:29,540 And that's not the form of that sentence is it. You say chair is blue chair was comfortable for. 460 00:50:29,540 --> 00:50:33,950 Gone. Not quite. No, what we've got here. 461 00:50:33,950 --> 00:50:38,180 This is a very interesting ambiguity here. 462 00:50:38,180 --> 00:50:48,010 Is is a very slippery word in English is you can have the is of predication. 463 00:50:48,010 --> 00:50:56,090 And the is of identity. And your attempted argument there. 464 00:50:56,090 --> 00:50:57,580 And don't worry about this at all. 465 00:50:57,580 --> 00:51:07,550 This is a perfectly reasonable mistake to make you equivocated between these two is is so you said this chair is blue, is that right? 466 00:51:07,550 --> 00:51:12,620 Right. And then you said this chair is comfortable. Okay. 467 00:51:12,620 --> 00:51:21,790 Now this. Well, actually, those those are both houses of predication, aren't they? 468 00:51:21,790 --> 00:51:27,880 Whereas what we're looking for here is is of identity, isn't it? 469 00:51:27,880 --> 00:51:31,840 A is B is the very same thing as B. 470 00:51:31,840 --> 00:51:38,140 So here we've got a predication, haven't we? A is F, A has a certain property. 471 00:51:38,140 --> 00:51:43,180 And here we have this thing. A is the same thing as this thing. 472 00:51:43,180 --> 00:51:50,050 B, therefore B is F K you see how that has to be true. 473 00:51:50,050 --> 00:51:53,800 This is a it's a law of logic. This one, isn't it. This is life. It's law. 474 00:51:53,800 --> 00:51:58,660 It is the law of logic. If A is F. If Marijan is tall. 475 00:51:58,660 --> 00:52:06,820 Oh. I'm just giving you the same example. So let me give it to you. If Jane is tall and Jane is the bank manager. 476 00:52:06,820 --> 00:52:14,730 Here's an is of Prescod predications. So we're predicating tallness of Jane Artley with me. 477 00:52:14,730 --> 00:52:21,350 On the Hill, we've got the issues of identity, haven't we? Jane is the bank manager. 478 00:52:21,350 --> 00:52:31,150 OK. If that's true and that's true, that has to be true, doesn't it, because the bank manager is Jane, isn't she? 479 00:52:31,150 --> 00:52:33,400 Yes, that is exactly that's what we're doing. 480 00:52:33,400 --> 00:52:41,170 We're looking at examples of deductively valid arguments, arguments that are valid by virtue of their form. 481 00:52:41,170 --> 00:52:46,000 OK. Good. One last one, I think. Here's a syllogism. Now, this should be easy. 482 00:52:46,000 --> 00:52:53,610 All FSG. A is an F, therefore, A is G. All Fords are cars. 483 00:52:53,610 --> 00:52:58,330 Okay. A is a Ford. Therefore, A is a car. 484 00:52:58,330 --> 00:53:03,660 Yes. Well done. That stuff. Do anyone else want to give one more example and we'll move on. 485 00:53:03,660 --> 00:53:07,200 Good. I see where you're getting to. Yeah, the grandma got a bit mixed up, but. 486 00:53:07,200 --> 00:53:14,340 Yes. Okay. So all my clothes are wet. That's pair of jeans is one of my clothes. 487 00:53:14,340 --> 00:53:18,210 Sort of. Therefore it is wet. I see where you're coming from. 488 00:53:18,210 --> 00:53:25,350 Okay. You've got them. OK. 489 00:53:25,350 --> 00:53:31,560 All miracles are impossible. Resurrection is a miracle. 490 00:53:31,560 --> 00:53:37,040 Therefore, they're OK. It works, doesn't it? Well done. We knew we'd get there somewhere. 491 00:53:37,040 --> 00:53:42,930 It's deadly this. Let me just give you a logical problem with that just because I think you might enjoy it. 492 00:53:42,930 --> 00:53:47,010 You said the resurrection is a miracle. 493 00:53:47,010 --> 00:53:49,680 Therefore, the resurrection is impossible. 494 00:53:49,680 --> 00:53:57,930 There's something very logically fishy about negative X and true negative existential sentences, isn't there? 495 00:53:57,930 --> 00:54:10,350 If we say Pegasus doesn't exist, aren't we picking out something by the word Pegasus in order to say all it that it doesn't exist? 496 00:54:10,350 --> 00:54:16,330 In which case, how can a negative assistant should be true? See what I mean? 497 00:54:16,330 --> 00:54:20,470 Hamlet doesn't exist. You're picking out something. Hamlet. 498 00:54:20,470 --> 00:54:24,940 In order to say off him that he doesn't exist. Well, how can you do that? 499 00:54:24,940 --> 00:54:31,210 You shouldn't be able to do that. I'll just leave you with a little conundrum, because that's philosophical logic. 500 00:54:31,210 --> 00:54:37,540 And we're not doing that here. We're doing symbolic logic here. So now you know of two different types of logic. 501 00:54:37,540 --> 00:54:41,500 Okay, we've there's there's the canonical example for that one. 502 00:54:41,500 --> 00:54:49,510 All men are mortal. Da da, da, da. Now, I said that some arguments and deductive, valid, deductively valid, but not in virtue of their form. 503 00:54:49,510 --> 00:54:55,300 Here is just a couple. This Eveillard in virtue of their content, apparently, Daylon. 504 00:54:55,300 --> 00:55:01,570 Tech logic. Now this is cutting edge stuff we know very little about. 505 00:55:01,570 --> 00:55:06,960 Day on tech logic, logic, day on tech. Logic is the logic of morality. 506 00:55:06,960 --> 00:55:15,310 Okay. What we're trying to look at is the area of discourse in which we talk about morality and say, how does it work logically? 507 00:55:15,310 --> 00:55:21,730 How can we get a valid argument form from more talk of morality? 508 00:55:21,730 --> 00:55:26,770 Now, look at this argument. Lying is wrong. Therefore, we shouldn't lie. 509 00:55:26,770 --> 00:55:32,390 Now, that looks like a deductively valid argument, doesn't it? 510 00:55:32,390 --> 00:55:38,530 In other words, if that's true. Surely this must be true as well. 511 00:55:38,530 --> 00:55:43,330 But if so, it's not true in virtue of its form. It's true in virtue of its what could you say? 512 00:55:43,330 --> 00:55:48,860 Lying is wrong. But I'm going to light. Well, we all know that you could lie. 513 00:55:48,860 --> 00:55:56,080 But you say if you truly believe that lying is wrong, you're also going to believe you shouldn't lie. 514 00:55:56,080 --> 00:56:04,030 Now, that doesn't mean you won't lie. But you'll feel guilty of doing that. 515 00:56:04,030 --> 00:56:11,110 That's just what I said. I said, if you believe lying is wrong, then you're going to believe you shouldn't lie, aren't you? 516 00:56:11,110 --> 00:56:23,170 Do you think you could possibly believe that lie? Really believe that lying is wrong and yet not believed that you shouldn't lie. 517 00:56:23,170 --> 00:56:30,070 Well, I think that if you find it okay, if you lie, either you're going to feel shame, which manifests your belief that lying. 518 00:56:30,070 --> 00:56:33,400 You do think lines wrong or you don't going to feel any shame at all. 519 00:56:33,400 --> 00:56:40,720 Which manifests manifests the fact that you don't believe that lying is always and everywhere wrong being wrong. 520 00:56:40,720 --> 00:56:45,930 Oh, don't get me on that. I'm not going to follow that one up at all. 521 00:56:45,930 --> 00:56:51,950 Oh, it's very important. Yes, but we're not. But but actually, we can safely leave it on one side here. 522 00:56:51,950 --> 00:56:57,370 You if you're a Kantian, you think that this entails that instant. 523 00:56:57,370 --> 00:57:03,950 You might want to put another premise in here. You might want to say we shouldn't do things that are wrong. 524 00:57:03,950 --> 00:57:10,600 Did someone want to do that? Okay. Kant would say if you did that, you would. 525 00:57:10,600 --> 00:57:18,490 You're manifesting the facts that you think that you could believe that something's wrong without believing you shouldn't do it. 526 00:57:18,490 --> 00:57:22,780 And that just shows you don't understand what wrongness is. 527 00:57:22,780 --> 00:57:29,920 To count, to have the proper moral concept, which is that, you know, lying is wrong or something like that, 528 00:57:29,920 --> 00:57:36,910 you cannot believe that something is wrong without also believing you shouldn't do it. 529 00:57:36,910 --> 00:57:41,500 So it doesn't mean you won't do it, because we all know that we do things we believe to be wrong. 530 00:57:41,500 --> 00:57:45,850 But but your belief that it's wrong will manifest itself as guilt. 531 00:57:45,850 --> 00:57:50,830 And if it doesn't, it manifests the fact you don't believe the first thing that lying is wrong. 532 00:57:50,830 --> 00:57:58,360 So anyway, we're not going to get into morality. I just wanted to say there is a logic type of logic called day on tick logic. 533 00:57:58,360 --> 00:58:03,070 And it looks at that sort of inference and notice that that's common. 534 00:58:03,070 --> 00:58:09,760 We can't give you a form for that. That's the very meaning of the word wrong. 535 00:58:09,760 --> 00:58:14,590 There's something very special about the meaning of the word wrong. Logically. 536 00:58:14,590 --> 00:58:22,600 Here's another one. Modal logic. Modal logic is the logic of necessity and possibility. 537 00:58:22,600 --> 00:58:29,290 It's necessarily the case that there are no square circles. In other words, there's no possible world in which there's a square circle. 538 00:58:29,290 --> 00:58:37,030 If it's square, it's not circular and so on. Therefore, it's not possible that there are square circles. 539 00:58:37,030 --> 00:58:44,660 So if P is necessarily true, then not P is not possible. 540 00:58:44,660 --> 00:58:50,030 Can you hear that? Oh, your capacity for reason would follow that quite quickly. 541 00:58:50,030 --> 00:58:56,350 If A is necessary, then not A is not possible. 542 00:58:56,350 --> 00:59:04,750 Got to be the case, hasn't it? So, again, we have a deductively valid argument, but it's not deductively valid at least. 543 00:59:04,750 --> 00:59:09,610 Actually, we're a lot further on with modal logic than we are in Day Ontake logic. 544 00:59:09,610 --> 00:59:16,090 We can do quite a lot with modal logic these days. And here's a bit of temporal logic for you. 545 00:59:16,090 --> 00:59:22,240 It's raining today. Therefore, tomorrow it will have been raining yesterday. 546 00:59:22,240 --> 00:59:27,820 Is that true? Okay. If that's true, then that must be true, mustn't it? 547 00:59:27,820 --> 00:59:34,140 Couldn't not. And that's because of a temporal logic. The way the logic of time works. 548 00:59:34,140 --> 00:59:39,250 Okay, let's move on. Pretty much short of time here. 549 00:59:39,250 --> 00:59:43,790 Let's we'll move on to inductive arguments now, inductive arguments. 550 00:59:43,790 --> 00:59:53,050 Remember, what's the hallmark of an inductive argument is if the premises are true, the conclusion might be true. 551 00:59:53,050 --> 01:00:02,110 Probably is true. That's right. Okay. So the premises give us reason for believing the conclusion, but not in this case, certainty. 552 01:00:02,110 --> 01:00:06,280 They don't give us conclusive reason for the really, really cute conclusion. 553 01:00:06,280 --> 01:00:12,640 And that's because inductive arguments rely on the assumption of the uniformity of nature. 554 01:00:12,640 --> 01:00:18,490 That's what Hume calls it. David Hume. The idea that the future will be like the past. 555 01:00:18,490 --> 01:00:24,940 So if we've seen the sun rise every day in the history of the universe, we expect it to rise tomorrow. 556 01:00:24,940 --> 01:00:32,170 If every time we've come here for Marianne's lecture on Monday at two o'clock and Marianne's been lecturing at two o'clock will come on, 557 01:00:32,170 --> 01:00:38,910 we'll carry on doing that. And if we come on the seventh week, we'll be disappointed, sadly. 558 01:00:38,910 --> 01:00:42,820 Okay. It was quite a good reason for believing that Marianne would be lecturing on Monday 559 01:00:42,820 --> 01:00:46,750 at 2:00 that she has been lecturing at 2:00 every Monday for the last six weeks. 560 01:00:46,750 --> 01:00:50,060 But it's not conclusive. And so on. 561 01:00:50,060 --> 01:00:55,300 So we're we are one of the biggest problems of philosophy, in fact, 562 01:00:55,300 --> 01:01:03,010 is how do we justify can we justify this assumption, the assumption that the future is going to be like the past? 563 01:01:03,010 --> 01:01:13,250 Why should we think that the future has been like the past? Can anyone give me a reason exactly? 564 01:01:13,250 --> 01:01:19,400 Because it it has always been the case that the future has been like the past in the past. 565 01:01:19,400 --> 01:01:23,330 So that's a circular. Yes, exactly. 566 01:01:23,330 --> 01:01:30,290 Every time you try and justify the belief that the future is going to be like the past, you'll find yourself arguing in a circle. 567 01:01:30,290 --> 01:01:35,120 The only reason we think that that works is because it always has worked in the past. 568 01:01:35,120 --> 01:01:42,710 Therefore, we assume it will work that way in the future. But human beings just cannot not argue like that. 569 01:01:42,710 --> 01:01:50,630 It's very interesting. I was playing with my cat the other day and I noticed that it doesn't go in for inductive reasoning. 570 01:01:50,630 --> 01:01:54,830 If you do that with a cat. If you do it with a human being, the human being. 571 01:01:54,830 --> 01:02:00,200 Keep going and expect you to keep going. But the cat doesn't. If you stop it, it stops. 572 01:02:00,200 --> 01:02:05,570 You don't catch it just slightly. It was interesting. 573 01:02:05,570 --> 01:02:09,880 Anyway, that's what inductive arguments rely on. 574 01:02:09,880 --> 01:02:16,690 Okay. Tell me why this one. Tell me what it is we're assuming. 575 01:02:16,690 --> 01:02:21,070 Actually, this is a silly question, in fact, I don't like this question. I'm going to skip it. 576 01:02:21,070 --> 01:02:28,810 You can see why the assumption here is that because the sun has always done this, it will always continue doing that in the future. 577 01:02:28,810 --> 01:02:36,250 And the assumption here is that because in your experience, Marianne's always done this in the future, Marianne will always do this. 578 01:02:36,250 --> 01:02:41,830 But our backgrounds and knowledge comes in to say whether you think it's a strong argument or a weak argument. 579 01:02:41,830 --> 01:02:47,780 And I think you'll see that given what we know about physics, about astronomy, about the laws of nature. 580 01:02:47,780 --> 01:02:52,270 That is a strong argument given what we know about people and what they wear. 581 01:02:52,270 --> 01:02:59,240 That's a weak argument. But both of them rely on the assumption of the principle of the uniformity of nature. 582 01:02:59,240 --> 01:03:05,570 And there are sub categories within the category of inductive arguments. 583 01:03:05,570 --> 01:03:16,380 Here's one an argument from another analogy. A is like B, A is F, therefore, B is the F. 584 01:03:16,380 --> 01:03:26,190 OK. A is like B, a notice these smaller lowercase letters stand in for particular things, 585 01:03:26,190 --> 01:03:32,100 whereas letters like this stand in for either properties or sometimes sentences. 586 01:03:32,100 --> 01:03:40,740 But I tend to use P, Q, R for sentences and A four. 587 01:03:40,740 --> 01:03:43,850 Oh, actually, that should be a smaller case now. Now started explaining it. 588 01:03:43,850 --> 01:03:50,670 That should be smaller case of scrub that okay is like BASF, therefore B is F, you see how that works. 589 01:03:50,670 --> 01:03:54,900 And here's an example. The universe is like a pocket watch. 590 01:03:54,900 --> 01:04:02,010 A pocket watch has a designer. Therefore, the universe has a designer. You will you'll be familiar with that Pascals. 591 01:04:02,010 --> 01:04:10,910 No, it's not pastel. What is it? Paly, thank you. 592 01:04:10,910 --> 01:04:20,360 So the universe is like it was a pocket watch. A is the universe, B is a pocket watch. 593 01:04:20,360 --> 01:04:27,320 A is F. I've got this the wrong way round, haven't I? 594 01:04:27,320 --> 01:04:36,110 Here's your homework, take that argument and put it into into proper canonical, logical form. 595 01:04:36,110 --> 01:04:41,930 Come back and tell me where I've got that wrong visa. I've got several quite interesting little errors in there. 596 01:04:41,930 --> 01:04:47,300 Some of them are just in the logic that I'm using. And some of them were I've just transposed various things. 597 01:04:47,300 --> 01:04:52,770 It should be easy for you to see where I've gone wrong. Do it. 598 01:04:52,770 --> 01:04:58,390 And come in if you want to come to cheque that with me next week. I'm very happy to have a look at it. 599 01:04:58,390 --> 01:05:14,430 OK, George, come up with your own argument from analogy. Got time for one or two, perhaps. 600 01:05:14,430 --> 01:05:23,610 I there's someone over here who hasn't had a chance to so far. Yes. 601 01:05:23,610 --> 01:05:27,870 Okay. That would do. One of your premises isn't true. Well, actually, no. 602 01:05:27,870 --> 01:05:32,670 Yes. One of your. Well, I suppose a universe is like a cabbage, isn't it? In a room, roughly. 603 01:05:32,670 --> 01:05:38,980 So shape wise. Okay, well, then that would work. Yep. One more. 604 01:05:38,980 --> 01:05:43,940 Sorry it again. So Tricia's like Sylvia. 605 01:05:43,940 --> 01:05:48,200 She's good. Yeah, absolutely. That'll do good. 606 01:05:48,200 --> 01:05:52,370 We've got that. Let's have a look at another inductive. Can you see how that's inductive? 607 01:05:52,370 --> 01:06:03,850 By the way, why is that? Why does that depend on the principle of the uniform uniformity of nature? 608 01:06:03,850 --> 01:06:09,490 But it's again, we're assuming if one thing is like another in some ways, then it'll be like another. 609 01:06:09,490 --> 01:06:15,310 In other ways. So we're we're assuming the uniformity of nature, aren't we? 610 01:06:15,310 --> 01:06:20,640 So if it's like that in one way, it'll be like that in another way as well. 611 01:06:20,640 --> 01:06:26,700 Here's another argument, an argument from authority. Einstein is a brilliant physicist. 612 01:06:26,700 --> 01:06:31,110 Einstein says relativism is true. Therefore, relativism is true. 613 01:06:31,110 --> 01:06:36,330 Of course, we could put in a different thing here. Einstein says pacifism is the right creed. 614 01:06:36,330 --> 01:06:39,870 Therefore, pacifism is the right creed. What have we done there? 615 01:06:39,870 --> 01:06:46,590 We've changed a good argument to a bad argument. Why is one good and one bad? 616 01:06:46,590 --> 01:06:54,270 Because he is an authority on physics. That's right. And he isn't an authority on politics. 617 01:06:54,270 --> 01:07:00,480 So but we'll be looking at good and bad arguments from now on after next week. 618 01:07:00,480 --> 01:07:06,630 OK. Causal arguments. We look to cause ligaments briefly. Last week, every time an A occurs, a B occurs. 619 01:07:06,630 --> 01:07:11,340 Therefore A's cause. B. Now we have a huge tendency. 620 01:07:11,340 --> 01:07:16,710 And in fact, that tendency was manifested here last week in this very room, wasn't it, 621 01:07:16,710 --> 01:07:22,140 where we assume that where there is a correlation, there is also a causal relation? 622 01:07:22,140 --> 01:07:28,710 Well, we know that that's not true, is it? We know that there can be correlations without causal relations. 623 01:07:28,710 --> 01:07:34,830 But even so, we tend to our evidence for causation tends to rest on the correlation. 624 01:07:34,830 --> 01:07:41,790 So if every time it occurs a B occurs, we'll tend to think that A's cause B's. 625 01:07:41,790 --> 01:07:51,510 So we argue from observation of a correlation to an assertion about her, a causal relation. 626 01:07:51,510 --> 01:08:02,040 And just to say quickly that causal arguments can be deductive or inductive, depending on whether we're arguing from a causal claim or to one. 627 01:08:02,040 --> 01:08:05,880 So A's cause B there was an A. 628 01:08:05,880 --> 01:08:18,360 Therefore, there will be a there will be a B every time every observed A has been followed by B, therefore A's caused B, which of these is deductive? 629 01:08:18,360 --> 01:08:25,580 Left or right, my left. That's left deductive inductive. 630 01:08:25,580 --> 01:08:31,290 Yep, that's right. Can you see that's we're taking calls here what we're saying work. 631 01:08:31,290 --> 01:08:37,080 We're arguing to a causal claim, aren't we? From observations of correlation. 632 01:08:37,080 --> 01:08:42,270 And here we're arguing from a causal claim. Indeed. 633 01:08:42,270 --> 01:08:47,850 The conclusion of that one to a particular claim. 634 01:08:47,850 --> 01:08:52,930 OK. So. That's deductive. 635 01:08:52,930 --> 01:08:56,110 Well, you should be able to do this. Okay. That's the doctor. 636 01:08:56,110 --> 01:09:01,400 Because if that's true, if that's true and that's true, then that must be true. 637 01:09:01,400 --> 01:09:06,730 Okay, this is this might be true. And yet this be false. 638 01:09:06,730 --> 01:09:10,780 But even so, that is reason to believe that, isn't it? 639 01:09:10,780 --> 01:09:19,160 OK. It's just not conclusive reason. Whereas these are conclusive reason to believe that. 640 01:09:19,160 --> 01:09:23,960 Right. Your task for the week ahead. 641 01:09:23,960 --> 01:09:29,660 See if you can find in your newspaper, magazine or Baucau or wherever. 642 01:09:29,660 --> 01:09:38,150 I've said four, but that's entirely arbitrary. Just see if you can find some arguments that fit the patterns that we'd be looking at today. 643 01:09:38,150 --> 01:09:44,690 And you might also notice in your own behaviour, as you're talking to people, you'll find yourself. 644 01:09:44,690 --> 01:09:51,680 And I'm hoping to sensitise you to these logical words so that they can't go will go past without you. 645 01:09:51,680 --> 01:09:58,730 Thank you. So when you find yourself saying if, then that's a particularly good one, 646 01:09:58,730 --> 01:10:07,490 if then or therefore or since or things like that, catch yourself and try and work out what your argument was. 647 01:10:07,490 --> 01:10:12,230 Now, some of your argument is going to be far too complicated to work out like that at the moment. 648 01:10:12,230 --> 01:10:18,890 Stick to simple ones safe and find yourself offering a simple argument, if you dare. 649 01:10:18,890 --> 01:10:23,120 I said if you don't clean your room, then this would happen. You did not clean your room. 650 01:10:23,120 --> 01:10:25,190 Therefore, you know, 651 01:10:25,190 --> 01:10:33,560 this this sort of thing is what you're trying to find out for and have a look and see if you can fit them into the forms that we've given here. 652 01:10:33,560 --> 01:10:37,910 OK. And next week we're going to look at actually identifying arguments and setting them out. 653 01:10:37,910 --> 01:10:43,250 Logic bookstall. We've been doing that today, but we're going to do that with some rather more complicated arguments. 654 01:10:43,250 --> 01:10:48,500 Next week we're going to look at arguments that you might make in the pub or in a newspaper or something like that. 655 01:10:48,500 --> 01:10:52,100 We'll look at a few magazine leaders and things like that. Sorry. 656 01:10:52,100 --> 01:10:56,821 Newspaper leaders. That's it.