1 00:00:02,560 --> 00:00:10,655 It's been a long and winding road as the Beatles used to say, but we're finally at 2 00:00:10,655 --> 00:00:17,266 the last stages of reconstructing arguments. We've looked at stage one, 3 00:00:17,266 --> 00:00:24,241 which is close analysis. Stage two which is get down to basics. Stage three which 4 00:00:24,241 --> 00:00:31,215 is sharpen edges, stage four is organize parts, and we are doing stage five which 5 00:00:31,215 --> 00:00:37,651 is fill in gaps and we'll also get to stage six which is conclude. Stage five 6 00:00:37,651 --> 00:00:42,609 really consists of four separate steps. First we need to assess the argument for 7 00:00:42,609 --> 00:00:47,628 validity. Then we need to add suppressed premises. Enough of them to make it valid. 8 00:00:47,628 --> 00:00:52,693 Then we need to assess those suppressed premises for truth or falsehood. And then 9 00:00:52,693 --> 00:00:58,390 we need to qualify the suppressed premises in order to make them true. The whole goal 10 00:00:58,390 --> 00:01:03,753 is to make the suppressed premises both plausible for their truth, and enough to 11 00:01:03,753 --> 00:01:09,182 make the argument valid. So, these steps within the stage really do work in tandem 12 00:01:09,182 --> 00:01:14,276 together to try and make the argument good. We already learned how to assess 13 00:01:14,276 --> 00:01:18,874 validity. You simply ask, "Is it possible for the premises to be true and the 14 00:01:18,874 --> 00:01:23,715 conclusion false, and if so, the argument is not valid and if not, the argument is 15 00:01:23,715 --> 00:01:28,677 valid." And the way you figure out whether it's possible is you try to tell a story 16 00:01:28,677 --> 00:01:33,458 or describe a situation and if you can describe a coherent situation where the 17 00:01:33,458 --> 00:01:38,420 premises are true and the conclusion is false, then that show that the argument is 18 00:01:38,420 --> 00:01:43,262 not really valid. The main topic for today is, what do you do when you assess the 19 00:01:43,262 --> 00:01:48,145 argument for validity and you find out it's not valid?" And the answer is, you 20 00:01:48,145 --> 00:01:53,929 add suppressed premises, enough of them to make the argument valid. But that might 21 00:01:53,929 --> 00:01:58,874 seem like cheating. I mean, you start with an argument that's no good, it's not 22 00:01:58,874 --> 00:02:03,820 valid, and then you just throw in some extra premises in order to make it valid. 23 00:02:03,820 --> 00:02:08,752 Why is it that's just distorting the argument and making up something that 24 00:02:08,752 --> 00:02:14,014 wasn't there? The answer is that it's not really bad. And if it were bad, we'd all 25 00:02:14,014 --> 00:02:19,210 be in bad shape because in everyday life, people always take things for granted. 26 00:02:19,210 --> 00:02:24,406 They make assumptions. We do it too, and if we didn't, boy, our arguments would be 27 00:02:24,406 --> 00:02:28,813 really long and boring. So there's something to be said in favor of 28 00:02:28,813 --> 00:02:33,680 suppressing premises, at least, the obvious ones that people really do take 29 00:02:33,680 --> 00:02:39,520 for granted. But we can also get tricked. People can suppress premises that really 30 00:02:39,520 --> 00:02:45,156 are questionable, and they just don't want us to see that they're making that 31 00:02:45,156 --> 00:02:50,623 assumption. So, it's useful to fill out the argument with suppressed premises to 32 00:02:50,623 --> 00:02:55,762 make sure it really is valid, because that brings those assumptions out in the open, 33 00:02:55,762 --> 00:03:00,900 where we can assess whether or not they're true or false. Another reason to fill in 34 00:03:00,900 --> 00:03:05,576 suppressed premises is to understand the argument better. Because if people 35 00:03:05,576 --> 00:03:10,798 suppress premises, then they're showing us some of their footprints along the path. 36 00:03:10,798 --> 00:03:15,893 But if we really want to know the full path that their reasoning followed, we've 37 00:03:15,893 --> 00:03:20,684 got to see every single footprint. So, the goal of bringing up the suppressed 38 00:03:20,684 --> 00:03:25,927 premises is to let us trace exactly where the reasoning is from one step to another. 39 00:03:25,927 --> 00:03:30,796 So there are two goals: One is to trace the full path every step and the other 40 00:03:30,796 --> 00:03:36,040 goal is to see if there are any miss-steps or they are trying to hid something from 41 00:03:36,040 --> 00:03:40,784 us by getting rid of one of their footsteps, so that's the point of bringing 42 00:03:40,784 --> 00:03:45,900 up suppressed premises. To accomplish these goals is tricky. You have to find 43 00:03:45,900 --> 00:03:51,225 suppressed premises that are just strong enough to make the argument valid but not 44 00:03:51,225 --> 00:03:56,550 so strong that there gonna be implausible. Cuz you don't wanna ascribe all kinds of 45 00:03:56,550 --> 00:04:01,362 suppressed premises to the person that they didn't really believe, and they 46 00:04:01,362 --> 00:04:06,751 didn't really need for their argument. So it's kind of like Goldilocks and the Three 47 00:04:06,751 --> 00:04:11,820 Bears. You want suppressed premises to be not too hot and not too cold, but just 48 00:04:11,820 --> 00:04:17,754 right. Here's an example from a previous lecture. My wife always gives me either a 49 00:04:17,754 --> 00:04:24,156 sweater or a board game. This box does not contain a sweater because it rattles when 50 00:04:24,156 --> 00:04:29,947 it's shaken so this time she must have given me a board game. We put this in 51 00:04:29,947 --> 00:04:35,967 standard form this way. First premise: This box rattles wh en I shake it and that 52 00:04:35,967 --> 00:04:42,853 shows you it doesn't contain a sweater. Third, she always gives me either a 53 00:04:42,853 --> 00:04:49,180 sweater or a board game. Conclusion, this time she must have given me a board game. 54 00:04:50,220 --> 00:04:56,584 Now the first step in this argument is, this box rattles when I shake it. And the 55 00:04:56,584 --> 00:05:02,649 conclusion there is it doesn't contain a sweater. That's the part of the argument 56 00:05:02,649 --> 00:05:08,640 we want to focus on here and ask whether that argument is valid. The argument is 57 00:05:08,640 --> 00:05:14,480 not valid, because it's possible for the premise to be true and the conclusion 58 00:05:14,480 --> 00:05:19,674 false. How can that happen? Well, my wife might be fooling me. She might know that I 59 00:05:19,674 --> 00:05:24,861 expect either a sweater or a board game, so she puts a sweater in the box. And then 60 00:05:24,861 --> 00:05:29,921 she puts little rocks around the outside so when I shake it, I'll hear something. 61 00:05:29,921 --> 00:05:35,040 So that's possible, and that shows that the argument's not valid. Well, how can we 62 00:05:35,040 --> 00:05:40,529 make the argument valid? The question here is, can we add a suppressed premise that 63 00:05:40,529 --> 00:05:45,750 will turn this invalid argument into a valid argument? Here's one that will do 64 00:05:45,750 --> 00:05:51,792 the trick. A box that contains a sweater doesn't rattle when shaken. Now the 65 00:05:51,792 --> 00:05:57,556 argument looks like this. This box rattles when I shake it. The box that contains a 66 00:05:57,556 --> 00:06:02,969 sweater doesn't rattle when shaken, so this box doesn't contain a sweater. The 67 00:06:02,969 --> 00:06:08,874 explicit premise is that this box rattles when I shake it. The suppressed premise is 68 00:06:08,874 --> 00:06:14,779 that a box that contains a sweater doesn't rattle when shaken and together they are 69 00:06:14,779 --> 00:06:20,614 suppose support the conclusion that this box doesn't contain a sweater, but do they 70 00:06:20,614 --> 00:06:26,521 really support that conclusion? Is the argument valid? Well, it's valid only if 71 00:06:26,521 --> 00:06:31,275 there's no possibility that the premises are true and the conclusions false. 72 00:06:31,275 --> 00:06:36,468 Without the suppressed premise we saw this might be possible, because my wife might 73 00:06:36,468 --> 00:06:41,097 be fooling me and putting rocks around the sweater. So let's see if that's going to 74 00:06:41,472 --> 00:06:45,972 ruin the validity of this argument. No! Because if the sweater has got rocks 75 00:06:45,972 --> 00:06:51,090 around it so it makes noise when I shake it, then the premise that says a box that 76 00:06:51,090 --> 00:06:55,331 contains a sweater doesn't rattle when shaken turns out to be fal se. 77 00:06:55,335 --> 00:07:00,641 So that's not a case where the premises are true and the conclusions false because 78 00:07:00,641 --> 00:07:05,759 the premise is false in that case. So, by adding this premise, we actually succeeded 79 00:07:05,759 --> 00:07:11,866 in making the argument valid. The problem of course is that validity is not enough 80 00:07:11,866 --> 00:07:17,843 for a good argument, as we saw several lectures ago. You can have an argument 81 00:07:17,843 --> 00:07:23,742 that's very bad, when the argument is not sound. What we want really is soundness. 82 00:07:23,742 --> 00:07:29,347 So, that's why we need the next step, mainly, check the supressed premises for 83 00:07:29,347 --> 00:07:34,951 truth. Assess whether they're true or false. And, if they're not true, then you 84 00:07:34,951 --> 00:07:40,850 need to qualify them, in order to make them true. Cuz you don't want to claim 85 00:07:40,850 --> 00:07:46,750 that the person giving the argument was assuming this falsehood, when the didn't 86 00:07:46,750 --> 00:07:52,706 have to. So let's see if there's some way to qualify this suppressed premise in 87 00:07:52,706 --> 00:08:00,037 order to make it true. How can we qualify this premise to make it true? How are we 88 00:08:00,037 --> 00:08:06,833 going to do that? Let me think. Oh. What about that little word only. You could add 89 00:08:06,833 --> 00:08:15,020 that. You could say, a box that contains only a sweater doesn't rattle when shaken. 90 00:08:15,620 --> 00:08:20,919 But the word only, what exactly does that mean? We need to clarify that. What 91 00:08:20,919 --> 00:08:26,430 exactly is the word only exclude? It excludes something, that's the function of 92 00:08:26,430 --> 00:08:32,684 the word only, but what does it exclude? Well. It probably excludes other things 93 00:08:32,684 --> 00:08:38,918 that might make the rattling sound like if my wife put rocks in the box. So we can 94 00:08:38,918 --> 00:08:45,228 clarify this premise by saying a box that contains only a sweater and not anything 95 00:08:45,228 --> 00:08:51,524 else that might make a rattling sound when shaken, won't rattle when shaken. Well, is 96 00:08:51,524 --> 00:08:57,538 that premise true? Well, you might quibble about details but it's close enough for 97 00:08:57,538 --> 00:09:03,330 now. What we need to do though is to go back and determine whether, when we put 98 00:09:03,330 --> 00:09:09,270 that suppressed premise in, the argument's valid. And the argument now looks like 99 00:09:09,270 --> 00:09:15,285 this. This box does rattle when shaken, and a box doesn't rattle when shaken if it 100 00:09:15,285 --> 00:09:21,769 contains only a sweater and not anything else that makes a rattling sound. So this 101 00:09:21,769 --> 00:09:29,492 box doesn't contain a sweater. Is that valid? Well, no, for the same reason we s 102 00:09:29,492 --> 00:09:35,456 aw before, because my wife might be a trickster who puts rocks around my sweater 103 00:09:35,456 --> 00:09:41,580 in the birthday present box in order to fool me. Then, the premises can be true, 104 00:09:41,580 --> 00:09:48,401 and the conclusion false. It's possible that, the first premise is true. This box 105 00:09:48,401 --> 00:09:54,907 rattles when I shake it. And the second premise is true, a box doesn't rattle when 106 00:09:54,907 --> 00:10:00,450 shaken if it contains only a sweater and nothing else that makes a rattling sound. 107 00:10:00,450 --> 00:10:04,799 But it's false that this box doesn't contain a sweater, cuz it still does 108 00:10:04,799 --> 00:10:09,446 contain a sweater, and it contains a sweater in addition to those pesky little 109 00:10:09,446 --> 00:10:13,744 rocks that make all that rattling noise. Well, if your argument's not valid, we've 110 00:10:13,744 --> 00:10:18,038 got to go back to that other step and add another suppressed premise. Remember how I 111 00:10:18,038 --> 00:10:22,281 told you how these different steps within this stage work in tandem and what's 112 00:10:22,281 --> 00:10:25,903 happening is you've got to check it for validity, add a suppressed premise, 113 00:10:25,903 --> 00:10:30,042 recheck for validity, maybe add another suppressed premise, and that's what we're 114 00:10:30,042 --> 00:10:35,232 doing now. So what kind of suppressed premised can we add. Well, we could add my 115 00:10:35,232 --> 00:10:40,867 wife is not a trickster but basically that amounts to she wouldn't put rocks in a 116 00:10:40,867 --> 00:10:46,571 birthday present with a sweater in order to fool me. So we could make that a little 117 00:10:46,571 --> 00:10:52,000 more explicit by making the suppressed premise something like this. If this box 118 00:10:52,000 --> 00:10:57,704 contains a sweater, then it only contains a sweater and it doesn't include anything 119 00:10:57,704 --> 00:11:03,385 else that would make a rattling sound when shaken. And now we can stick that as an 120 00:11:03,385 --> 00:11:08,369 extra suppressed premise into the argument. Now the argument looks like 121 00:11:08,369 --> 00:11:14,846 this. This box rattles when I shake it. A box doesn't rattle when shaken, if it 122 00:11:14,846 --> 00:11:20,976 contains only a sweater and not anything else that makes a rattling noise when 123 00:11:20,976 --> 00:11:27,627 shaken. If this box contains a sweater, then it contains only a sweater and 124 00:11:27,627 --> 00:11:34,382 doesn't contain anything that rattles when shaken. So this box does not contain a 125 00:11:34,382 --> 00:11:39,775 sweater. Now we have an argument that's valid. And the suppressed premises are 126 00:11:39,775 --> 00:11:44,980 true, at least given our life's not a trickster, which she's not, I assure you. 127 00:11:44,980 --> 00:11:51,005 And it looks like we have a sound rec onstruction, just what we were looking 128 00:11:51,005 --> 00:11:56,351 for. Admittedly, this argument is a lot longer and more convoluted than the 129 00:11:56,351 --> 00:12:01,685 original, and that shows why people suppress premises instead of talking the 130 00:12:01,685 --> 00:12:06,774 way this argument goes. And of course, many people would be perfectly well 131 00:12:06,774 --> 00:12:12,750 convinced by the original argument because they share the assumptions that are in the 132 00:12:12,750 --> 00:12:18,240 suppressed premises. So why do we go through all the trouble to go through this 133 00:12:18,240 --> 00:12:22,896 process and add the suppressed premises? Remember, the reason is that we want to 134 00:12:23,313 --> 00:12:27,621 understand the pathway between the premises and conclusion. We want to 135 00:12:28,038 --> 00:12:33,228 understand how the reasoning works step by step by step. And we want to do that 136 00:12:33,228 --> 00:12:37,632 because sometimes people are going to include suppressed premises that aren't 137 00:12:37,632 --> 00:12:42,261 true, and we want to bring them out and make those assumptions explicit so that we 138 00:12:42,261 --> 00:12:46,881 can assess them for truth and falsehood. And when you're talking to somebody you 139 00:12:46,881 --> 00:12:51,605 trust, you might not have to do that and it's okay to suppress premises. But when 140 00:12:51,605 --> 00:12:56,151 you really want to know whether the argument's any good, that's when you want 141 00:12:56,151 --> 00:13:00,579 to fill it out with the suppressed premises. The point of going into detail 142 00:13:00,579 --> 00:13:04,992 on this example is to illustrate this stage of reconstruction. You want to 143 00:13:04,992 --> 00:13:09,757 assess the argument for validity, add suppressed premises that make it valid. 144 00:13:09,757 --> 00:13:14,710 Check them for truth. If they're not true, you qualify them, and then you go back and 145 00:13:14,710 --> 00:13:19,600 see whether that qualification made the argument not valid anymore. And you go 146 00:13:19,600 --> 00:13:24,508 back and forth and back and forth until you've got a sound reconstruction. The 147 00:13:24,508 --> 00:13:29,807 same steps are going to apply to all kinds of suppressed premises. And sure enough, 148 00:13:29,807 --> 00:13:34,436 there are all kinds of suppressed premises. So let's go through a few 149 00:13:34,436 --> 00:13:39,802 examples a lot more quickly in order to show the variety of suppressed premises 150 00:13:39,802 --> 00:13:46,782 that are assumed in arguments. Here's one example. Abraham Lincoln turned 40. On 151 00:13:46,782 --> 00:13:57,957 February twelfth, 1849. Therefore, Charles Darwin also turned 40 on February twelfth, 152 00:13:57,957 --> 00:14:04,109 1849. Now, is that argument valid? No chance. Of course it's possible for the 153 00:14:04,109 --> 00:14:09,576 premise to be true and the conclus ion false. So we have to add a suppressed 154 00:14:09,576 --> 00:14:15,309 premise. The suppressed premise is, that Abraham Lincoln and Charles Darwin were 155 00:14:15,309 --> 00:14:20,637 born on the same day. And they were, it happened to be February twelfth, 1809. So 156 00:14:20,637 --> 00:14:27,132 now, we've filled out the argument. Abraham Lincoln turned 40 on February 157 00:14:27,132 --> 00:14:33,451 twelfth, 1849. Abraham Lincoln and Charles Darwin were born on the same day, 158 00:14:33,451 --> 00:14:39,545 therefore Charles Darwin also turned 40 on February twelfth, 1849. Now is the 159 00:14:39,545 --> 00:14:46,682 argument valid? No. It's still not valid. Cuz Darwin might have died before 1849. So 160 00:14:46,682 --> 00:14:53,017 we have to add another suppressed premise. Mainly, that both Abraham Lincoln and 161 00:14:53,017 --> 00:14:59,665 Charles Darwin lived beyond 40. So now we have a fuller argument. Abraham Lincoln 162 00:14:59,665 --> 00:15:07,033 turned 40 on February twelfth, 1849. Abraham Lincoln and Charles Darwin were 163 00:15:07,033 --> 00:15:14,406 born on the same day. Both of them lived beyond the age of 40. Therefore, Charles 164 00:15:14,406 --> 00:15:20,997 Darwin also turned 40 on February twelve, 1849. Now the argument looks pretty good. 165 00:15:20,997 --> 00:15:26,576 We had to have two suppressed premises but we finally have a valid argument. And what 166 00:15:26,576 --> 00:15:31,301 this shows is that sometimes the suppressed premises are purely factual 167 00:15:31,301 --> 00:15:36,683 matters. In this case that they were born on the same day and that they both lived 168 00:15:36,683 --> 00:15:42,077 beyond 40. So sometimes we have factual suppressed premises. Here's another quick 169 00:15:42,077 --> 00:15:46,952 example. You ought to obey her because she's your mother. Here, the premise is 170 00:15:46,952 --> 00:15:52,445 that she's your mother and the conclusion is that you ought to obey her. Well, is 171 00:15:52,445 --> 00:15:57,870 that argument valid? No way cause it's possible that she's your mother but it's 172 00:15:57,870 --> 00:16:03,020 false that you ought to obey her. When could that happen? Maybe, she was like 173 00:16:03,020 --> 00:16:08,933 abusive or stupid or whatever. Then maybe you ought not to obey her even though she 174 00:16:08,933 --> 00:16:14,241 is your mother. So we have to add a premise, namely, you ought to obey your 175 00:16:14,241 --> 00:16:19,244 mother. Now we can say she's your mother, you ought to obey your mother therefore 176 00:16:19,244 --> 00:16:24,540 you ought to obey her, but of course that a supressed premise you ought to obey your 177 00:16:24,540 --> 00:16:29,219 mother is questionable because maybe she was abusive or stupid. So let's add 178 00:16:29,219 --> 00:16:34,268 another supressed premise that your mother was not abusive or stupid, of course we a 179 00:16:34,268 --> 00:16:39,071 lso have to qualify that moral premise that you ought to obey your mother if 180 00:16:39,071 --> 00:16:43,812 she's not abusive or stupid. And now the argument looks like this - she's your 181 00:16:43,812 --> 00:16:48,900 mother, you ought to obey your mother if she's not abusive or stupid. Your mother 182 00:16:48,900 --> 00:16:54,880 was not abusive or stupid. Therefore, you ought to obey her. An notice that here, we 183 00:16:54,880 --> 00:17:00,409 added a moral premise about the fact that you ought to obey your mother under 184 00:17:00,409 --> 00:17:05,867 certain conditions. Namely, she's not abusive or stupid. And the second premise 185 00:17:05,867 --> 00:17:11,042 is she was not abusive or stupid. So, we have a moral premise and a factual 186 00:17:11,042 --> 00:17:16,216 premise, both being suppressed in the argument that you ought to obey her 187 00:17:16,216 --> 00:17:22,633 because she's your mother. Here's another . It's the Sabbath, so you ought to go to 188 00:17:22,633 --> 00:17:28,521 synagogue. Well, that's clearly not valid. One suppressed premise is that you're 189 00:17:28,521 --> 00:17:34,291 Jewish. The other suppressed premise is you haven't been to synagogue already 190 00:17:34,291 --> 00:17:39,906 today, on this Sabbath. And the third suppressed premise is a religious norm, 191 00:17:39,906 --> 00:17:45,735 mainly Jews ought to go to the synagogue on the Sabbath. And you need that whole 192 00:17:45,735 --> 00:17:50,912 bunch of suppressed premises in order to get from the premise, that it's the 193 00:17:50,912 --> 00:17:56,339 Sabbath, to the conclusion, that you ought to go to synagogue. And of course all of 194 00:17:56,339 --> 00:18:01,504 those premises might be questionable. Some people would question them. Some people 195 00:18:01,504 --> 00:18:06,910 would deny them, but the point here is to figure out what's being assumed by someone 196 00:18:06,910 --> 00:18:11,814 who gave the original argument. And anybody who says it's the Sabbath, so you 197 00:18:11,814 --> 00:18:16,203 ought to go to synagogue, seems to be assuming you're Jewish, you haven't been 198 00:18:16,203 --> 00:18:21,152 already, and Jews ought to go to the synagogue on the Sabbath. So what these 199 00:18:21,152 --> 00:18:26,938 suppressed premises do is they bring out the assumptions that somebody who gave 200 00:18:26,938 --> 00:18:32,869 that argument must have had in mind. The last case is a little bit trickier. It has 201 00:18:32,869 --> 00:18:38,800 to do with linguistic suppressed premises. Jen and Bob are first cousins, therefore 202 00:18:38,800 --> 00:18:47,470 they share a grandparent. Now, in order to understand that argument, you have to know 203 00:18:47,470 --> 00:18:52,162 that first cousins always share a grandparent. That just follows from the 204 00:18:52,162 --> 00:18:58,847 definition of what a first cousin is. But i t's not quite so obvious, is that 205 00:18:58,847 --> 00:19:04,002 biological sisters are female. And so, there's even more need to bring out that 206 00:19:04,002 --> 00:19:09,356 linguistics suppressed premise in this case. But it's still not necessary to make 207 00:19:09,356 --> 00:19:14,843 the argument valid. It's just not possible that Janet and Bob are first cousins, and 208 00:19:14,843 --> 00:19:19,602 they don't share a grandparent. Because the suppressed premise is purely 209 00:19:19,602 --> 00:19:24,663 linguistic, so it's necessarily true, so you can't possibly be first cousins 210 00:19:24,663 --> 00:19:29,700 without sharing a grandparent. Still, the point of bringing out linguistic 211 00:19:29,700 --> 00:19:34,944 suppressed premises is to show every little step along the way. The argument 212 00:19:34,944 --> 00:19:39,952 might be valid without those suppressed linguistic premises, but we won't 213 00:19:39,952 --> 00:19:45,153 understand why it's valid and why the reasoning goes through unless we add the 214 00:19:45,153 --> 00:19:51,412 linguistics suppressed premise. So it's worth doing that. Shh. Here's a trick. 215 00:19:51,412 --> 00:20:00,400 Don't tell anybody. Okay? It's just between me and you. You can always make 216 00:20:00,400 --> 00:20:06,916 any argument valid just by adding a suppressed premise that says if the 217 00:20:06,916 --> 00:20:14,069 premises are true, then the conclusion is true. But don't tell anybody, because if 218 00:20:14,069 --> 00:20:19,991 people start doing that, and they start making the argument valid that way, with 219 00:20:19,991 --> 00:20:26,270 that suppressed premise, we're never going to understand the pathway of reasoning. It 220 00:20:26,270 --> 00:20:31,095 makes the argument valid, but it doesn't serve the real purpose of adding 221 00:20:31,578 --> 00:20:37,231 suppressed premises which is to understand the pathway of reasoning. So you can do 222 00:20:37,231 --> 00:20:42,677 that. It's a trick. It makes that argument valid but it doesn't achieve our goal 223 00:20:42,677 --> 00:20:48,330 because our goal is not just to make the argument valid, it's to make the argument 224 00:20:48,330 --> 00:20:54,604 valid so that we can understand the pathway of reasoning. So it's important to 225 00:20:54,604 --> 00:21:02,339 know that trick, but don't use it unless you have to. The examples so far have been 226 00:21:02,339 --> 00:21:07,850 pretty trivial, I admit it. But the same points apply in very important context 227 00:21:07,850 --> 00:21:13,573 such as politic debates, politician can suppress premises in perfectly legitimate 228 00:21:13,573 --> 00:21:19,508 ways. They're just trying to save time and make their arguments more efficient, maybe 229 00:21:19,508 --> 00:21:25,615 even sometimes clearer because you don't have to add all those little details. But 230 00:21:25,615 --> 00:21:31,684 sometimes politicia ns abuse suppressed premises. They take things for granted 231 00:21:31,684 --> 00:21:37,910 that they shouldn't be taking for granted. Here's an example. A politician might 232 00:21:37,910 --> 00:21:43,980 argue, my opponent is soft on crime because he's opposed to the death penalty. 233 00:21:44,300 --> 00:21:50,016 Well, that assumes, as a suppressed premise, that anyone who's opposed to the 234 00:21:50,016 --> 00:21:56,143 death penalty must be soft on crime. And if the politician were to come out and say 235 00:21:56,143 --> 00:22:01,460 that, it would seem pretty questionable, and that's probably why he suppresses it. 236 00:22:01,720 --> 00:22:07,446 And then another politician might say, my opponent is in favor of the death penalty, 237 00:22:07,446 --> 00:22:13,034 so he must not have read all the recent studies that show that the death penalty 238 00:22:13,034 --> 00:22:18,977 doesn't deter. Well that argument assumes the suppressed premise that if you've read 239 00:22:18,977 --> 00:22:23,556 those studies you'ld be convinced by them, and that the only point of the death 240 00:22:23,556 --> 00:22:29,642 penalty is deterrence. But the point is that politicians talking about extremely 241 00:22:29,642 --> 00:22:34,047 important issues can take things for granted, that if they were brought into 242 00:22:34,047 --> 00:22:38,858 the light of day will be questionable, and that's why they hide them. So when you're 243 00:22:38,858 --> 00:22:43,500 listening to people give arguments on important issues in your life, then you 244 00:22:43,500 --> 00:22:49,802 ought to be looking for these suppressed premises and asking yourself whether or 245 00:22:49,802 --> 00:22:55,949 not you really ought to be agreeing with them about that assumption. Finally, we 246 00:22:55,949 --> 00:23:01,628 finished reconstruction. Yipee, right? Oh, no, not quite, because there's one more 247 00:23:01,628 --> 00:23:06,951 stage, and that stage is drawing a conclusion. Of course, if we've come up 248 00:23:06,951 --> 00:23:12,349 with a sound reconstruction, then we know that the argument is sound, and we know 249 00:23:12,349 --> 00:23:18,817 that the conclusion is true, because every sound argument has a true conclusion. But 250 00:23:18,817 --> 00:23:23,519 if we don't come up with a sound reconstruction, then what do we say? Well, 251 00:23:23,519 --> 00:23:28,415 you've got to ask, whose fault is it? It might be the fault of the argument. Maybe 252 00:23:28,415 --> 00:23:33,117 we couldn't come up with a sound reconstruction because there just is no 253 00:23:33,117 --> 00:23:37,240 sound reconstruction. But maybe we couldn't come up with a sound 254 00:23:37,240 --> 00:23:42,200 reconstruction because we just weren't imaginative enough, or try hard enough. 255 00:23:42,200 --> 00:23:47,592 Still, if we try really long an hard, and charitably interpret the a rgument as best 256 00:23:47,592 --> 00:23:52,919 we can to make it, look as good as we can, and we still can't make it sound. Then, 257 00:23:52,919 --> 00:23:58,312 we've at least got reason to believe that the argument's not sound. Of course, that 258 00:23:58,312 --> 00:24:03,573 doesn't mean that the conclusion's not true, because unsound arguments can still 259 00:24:03,573 --> 00:24:09,107 have true conclusions. But at least we know that this argument doesn't prove that 260 00:24:09,107 --> 00:24:14,094 the conclusion is true. And so, this method of reconstruction can lead us 261 00:24:14,094 --> 00:24:19,290 either to the belief that the argument is sound, because we found the sound 262 00:24:19,290 --> 00:24:24,831 reconstruction, or to the conclusion is not sound, because we tried long and hard 263 00:24:24,831 --> 00:24:30,234 to find a sound reconstruction that didn't, but that's still not going to show 264 00:24:30,234 --> 00:24:36,546 us that the conclusion of the argument is false. The point of reconstruction then is 265 00:24:36,546 --> 00:24:42,347 to reach a conclusion on this issue of is the argument sound or not. And if we try 266 00:24:42,347 --> 00:24:48,007 our best and do it as well as we can and charitably, then we can be justified in 267 00:24:48,007 --> 00:24:51,120 believing that the argument is sound or not.