WEBVTT 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 00:00:10.655 --> 00:00:17.266 the last stages of reconstructing arguments. We've looked at stage one, 00:00:17.266 --> 00:00:24.241 which is close analysis. Stage two which is get down to basics. Stage three which 00:00:24.241 --> 00:00:31.215 is sharpen edges, stage four is organize parts, and we are doing stage five which 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 00:00:37.651 --> 00:00:42.609 really consists of four separate steps. First we need to assess the argument for 00:00:42.609 --> 00:00:47.628 validity. Then we need to add suppressed premises. Enough of them to make it valid. 00:00:47.628 --> 00:00:52.693 Then we need to assess those suppressed premises for truth or falsehood. And then 00:00:52.693 --> 00:00:58.390 we need to qualify the suppressed premises in order to make them true. The whole goal 00:00:58.390 --> 00:01:03.753 is to make the suppressed premises both plausible for their truth, and enough to 00:01:03.753 --> 00:01:09.182 make the argument valid. So, these steps within the stage really do work in tandem 00:01:09.182 --> 00:01:14.276 together to try and make the argument good. We already learned how to assess 00:01:14.276 --> 00:01:18.874 validity. You simply ask, "Is it possible for the premises to be true and the 00:01:18.874 --> 00:01:23.715 conclusion false, and if so, the argument is not valid and if not, the argument is 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 00:01:28.677 --> 00:01:33.458 or describe a situation and if you can describe a coherent situation where the 00:01:33.458 --> 00:01:38.420 premises are true and the conclusion is false, then that show that the argument is 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 00:01:43.262 --> 00:01:48.145 argument for validity and you find out it's not valid?" And the answer is, you 00:01:48.145 --> 00:01:53.929 add suppressed premises, enough of them to make the argument valid. But that might 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 00:01:58.874 --> 00:02:03.820 valid, and then you just throw in some extra premises in order to make it valid. 00:02:03.820 --> 00:02:08.752 Why is it that's just distorting the argument and making up something that 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 00:02:14.014 --> 00:02:19.210 be in bad shape because in everyday life, people always take things for granted. 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 00:02:24.406 --> 00:02:28.813 really long and boring. So there's something to be said in favor of 00:02:28.813 --> 00:02:33.680 suppressing premises, at least, the obvious ones that people really do take 00:02:33.680 --> 00:02:39.520 for granted. But we can also get tricked. People can suppress premises that really 00:02:39.520 --> 00:02:45.156 are questionable, and they just don't want us to see that they're making that 00:02:45.156 --> 00:02:50.623 assumption. So, it's useful to fill out the argument with suppressed premises to 00:02:50.623 --> 00:02:55.762 make sure it really is valid, because that brings those assumptions out in the open, 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 00:03:00.900 --> 00:03:05.576 suppressed premises is to understand the argument better. Because if people 00:03:05.576 --> 00:03:10.798 suppress premises, then they're showing us some of their footprints along the path. 00:03:10.798 --> 00:03:15.893 But if we really want to know the full path that their reasoning followed, we've 00:03:15.893 --> 00:03:20.684 got to see every single footprint. So, the goal of bringing up the suppressed 00:03:20.684 --> 00:03:25.927 premises is to let us trace exactly where the reasoning is from one step to another. 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 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 00:03:36.040 --> 00:03:40.784 us by getting rid of one of their footsteps, so that's the point of bringing 00:03:40.784 --> 00:03:45.900 up suppressed premises. To accomplish these goals is tricky. You have to find 00:03:45.900 --> 00:03:51.225 suppressed premises that are just strong enough to make the argument valid but not 00:03:51.225 --> 00:03:56.550 so strong that there gonna be implausible. Cuz you don't wanna ascribe all kinds of 00:03:56.550 --> 00:04:01.362 suppressed premises to the person that they didn't really believe, and they 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 00:04:06.751 --> 00:04:11.820 Bears. You want suppressed premises to be not too hot and not too cold, but just 00:04:11.820 --> 00:04:17.754 right. Here's an example from a previous lecture. My wife always gives me either a 00:04:17.754 --> 00:04:24.156 sweater or a board game. This box does not contain a sweater because it rattles when 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 00:04:29.947 --> 00:04:35.967 standard form this way. First premise: This box rattles wh en I shake it and that 00:04:35.967 --> 00:04:42.853 shows you it doesn't contain a sweater. Third, she always gives me either a 00:04:42.853 --> 00:04:49.180 sweater or a board game. Conclusion, this time she must have given me a board game. 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 00:04:56.584 --> 00:05:02.649 conclusion there is it doesn't contain a sweater. That's the part of the argument 00:05:02.649 --> 00:05:08.640 we want to focus on here and ask whether that argument is valid. The argument is 00:05:08.640 --> 00:05:14.480 not valid, because it's possible for the premise to be true and the conclusion 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 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 00:05:24.861 --> 00:05:29.921 she puts little rocks around the outside so when I shake it, I'll hear something. 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 00:05:35.040 --> 00:05:40.529 make the argument valid? The question here is, can we add a suppressed premise that 00:05:40.529 --> 00:05:45.750 will turn this invalid argument into a valid argument? Here's one that will do 00:05:45.750 --> 00:05:51.792 the trick. A box that contains a sweater doesn't rattle when shaken. Now the 00:05:51.792 --> 00:05:57.556 argument looks like this. This box rattles when I shake it. The box that contains a 00:05:57.556 --> 00:06:02.969 sweater doesn't rattle when shaken, so this box doesn't contain a sweater. The 00:06:02.969 --> 00:06:08.874 explicit premise is that this box rattles when I shake it. The suppressed premise is 00:06:08.874 --> 00:06:14.779 that a box that contains a sweater doesn't rattle when shaken and together they are 00:06:14.779 --> 00:06:20.614 suppose support the conclusion that this box doesn't contain a sweater, but do they 00:06:20.614 --> 00:06:26.521 really support that conclusion? Is the argument valid? Well, it's valid only if 00:06:26.521 --> 00:06:31.275 there's no possibility that the premises are true and the conclusions false. 00:06:31.275 --> 00:06:36.468 Without the suppressed premise we saw this might be possible, because my wife might 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 00:06:41.472 --> 00:06:45.972 ruin the validity of this argument. No! Because if the sweater has got rocks 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 00:06:51.090 --> 00:06:55.331 contains a sweater doesn't rattle when shaken turns out to be fal se. 00:06:55.335 --> 00:07:00.641 So that's not a case where the premises are true and the conclusions false because 00:07:00.641 --> 00:07:05.759 the premise is false in that case. So, by adding this premise, we actually succeeded 00:07:05.759 --> 00:07:11.866 in making the argument valid. The problem of course is that validity is not enough 00:07:11.866 --> 00:07:17.843 for a good argument, as we saw several lectures ago. You can have an argument 00:07:17.843 --> 00:07:23.742 that's very bad, when the argument is not sound. What we want really is soundness. 00:07:23.742 --> 00:07:29.347 So, that's why we need the next step, mainly, check the supressed premises for 00:07:29.347 --> 00:07:34.951 truth. Assess whether they're true or false. And, if they're not true, then you 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 00:07:40.850 --> 00:07:46.750 that the person giving the argument was assuming this falsehood, when the didn't 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 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 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 00:08:06.833 --> 00:08:15.020 that. You could say, a box that contains only a sweater doesn't rattle when shaken. 00:08:15.620 --> 00:08:20.919 But the word only, what exactly does that mean? We need to clarify that. What 00:08:20.919 --> 00:08:26.430 exactly is the word only exclude? It excludes something, that's the function of 00:08:26.430 --> 00:08:32.684 the word only, but what does it exclude? Well. It probably excludes other things 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 00:08:38.918 --> 00:08:45.228 clarify this premise by saying a box that contains only a sweater and not anything 00:08:45.228 --> 00:08:51.524 else that might make a rattling sound when shaken, won't rattle when shaken. Well, is 00:08:51.524 --> 00:08:57.538 that premise true? Well, you might quibble about details but it's close enough for 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 00:09:03.330 --> 00:09:09.270 that suppressed premise in, the argument's valid. And the argument now looks like 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 00:09:15.285 --> 00:09:21.769 contains only a sweater and not anything else that makes a rattling sound. So this 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 00:09:29.492 --> 00:09:35.456 aw before, because my wife might be a trickster who puts rocks around my sweater 00:09:35.456 --> 00:09:41.580 in the birthday present box in order to fool me. Then, the premises can be true, 00:09:41.580 --> 00:09:48.401 and the conclusion false. It's possible that, the first premise is true. This box 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 00:09:54.907 --> 00:10:00.450 shaken if it contains only a sweater and nothing else that makes a rattling sound. 00:10:00.450 --> 00:10:04.799 But it's false that this box doesn't contain a sweater, cuz it still does 00:10:04.799 --> 00:10:09.446 contain a sweater, and it contains a sweater in addition to those pesky little 00:10:09.446 --> 00:10:13.744 rocks that make all that rattling noise. Well, if your argument's not valid, we've 00:10:13.744 --> 00:10:18.038 got to go back to that other step and add another suppressed premise. Remember how I 00:10:18.038 --> 00:10:22.281 told you how these different steps within this stage work in tandem and what's 00:10:22.281 --> 00:10:25.903 happening is you've got to check it for validity, add a suppressed premise, 00:10:25.903 --> 00:10:30.042 recheck for validity, maybe add another suppressed premise, and that's what we're 00:10:30.042 --> 00:10:35.232 doing now. So what kind of suppressed premised can we add. Well, we could add my 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 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 00:10:46.571 --> 00:10:52.000 more explicit by making the suppressed premise something like this. If this box 00:10:52.000 --> 00:10:57.704 contains a sweater, then it only contains a sweater and it doesn't include anything 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 00:11:03.385 --> 00:11:08.369 extra suppressed premise into the argument. Now the argument looks like 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 00:11:14.846 --> 00:11:20.976 contains only a sweater and not anything else that makes a rattling noise when 00:11:20.976 --> 00:11:27.627 shaken. If this box contains a sweater, then it contains only a sweater and 00:11:27.627 --> 00:11:34.382 doesn't contain anything that rattles when shaken. So this box does not contain a 00:11:34.382 --> 00:11:39.775 sweater. Now we have an argument that's valid. And the suppressed premises are 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. 00:11:44.980 --> 00:11:51.005 And it looks like we have a sound rec onstruction, just what we were looking 00:11:51.005 --> 00:11:56.351 for. Admittedly, this argument is a lot longer and more convoluted than the 00:11:56.351 --> 00:12:01.685 original, and that shows why people suppress premises instead of talking the 00:12:01.685 --> 00:12:06.774 way this argument goes. And of course, many people would be perfectly well 00:12:06.774 --> 00:12:12.750 convinced by the original argument because they share the assumptions that are in the 00:12:12.750 --> 00:12:18.240 suppressed premises. So why do we go through all the trouble to go through this 00:12:18.240 --> 00:12:22.896 process and add the suppressed premises? Remember, the reason is that we want to 00:12:23.313 --> 00:12:27.621 understand the pathway between the premises and conclusion. We want to 00:12:28.038 --> 00:12:33.228 understand how the reasoning works step by step by step. And we want to do that 00:12:33.228 --> 00:12:37.632 because sometimes people are going to include suppressed premises that aren't 00:12:37.632 --> 00:12:42.261 true, and we want to bring them out and make those assumptions explicit so that we 00:12:42.261 --> 00:12:46.881 can assess them for truth and falsehood. And when you're talking to somebody you 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 00:12:51.605 --> 00:12:56.151 you really want to know whether the argument's any good, that's when you want 00:12:56.151 --> 00:13:00.579 to fill it out with the suppressed premises. The point of going into detail 00:13:00.579 --> 00:13:04.992 on this example is to illustrate this stage of reconstruction. You want to 00:13:04.992 --> 00:13:09.757 assess the argument for validity, add suppressed premises that make it valid. 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 00:13:14.710 --> 00:13:19.600 see whether that qualification made the argument not valid anymore. And you go 00:13:19.600 --> 00:13:24.508 back and forth and back and forth until you've got a sound reconstruction. The 00:13:24.508 --> 00:13:29.807 same steps are going to apply to all kinds of suppressed premises. And sure enough, 00:13:29.807 --> 00:13:34.436 there are all kinds of suppressed premises. So let's go through a few 00:13:34.436 --> 00:13:39.802 examples a lot more quickly in order to show the variety of suppressed premises 00:13:39.802 --> 00:13:46.782 that are assumed in arguments. Here's one example. Abraham Lincoln turned 40. On 00:13:46.782 --> 00:13:57.957 February twelfth, 1849. Therefore, Charles Darwin also turned 40 on February twelfth, 00:13:57.957 --> 00:14:04.109 1849. Now, is that argument valid? No chance. Of course it's possible for the 00:14:04.109 --> 00:14:09.576 premise to be true and the conclus ion false. So we have to add a suppressed 00:14:09.576 --> 00:14:15.309 premise. The suppressed premise is, that Abraham Lincoln and Charles Darwin were 00:14:15.309 --> 00:14:20.637 born on the same day. And they were, it happened to be February twelfth, 1809. So 00:14:20.637 --> 00:14:27.132 now, we've filled out the argument. Abraham Lincoln turned 40 on February 00:14:27.132 --> 00:14:33.451 twelfth, 1849. Abraham Lincoln and Charles Darwin were born on the same day, 00:14:33.451 --> 00:14:39.545 therefore Charles Darwin also turned 40 on February twelfth, 1849. Now is the 00:14:39.545 --> 00:14:46.682 argument valid? No. It's still not valid. Cuz Darwin might have died before 1849. So 00:14:46.682 --> 00:14:53.017 we have to add another suppressed premise. Mainly, that both Abraham Lincoln and 00:14:53.017 --> 00:14:59.665 Charles Darwin lived beyond 40. So now we have a fuller argument. Abraham Lincoln 00:14:59.665 --> 00:15:07.033 turned 40 on February twelfth, 1849. Abraham Lincoln and Charles Darwin were 00:15:07.033 --> 00:15:14.406 born on the same day. Both of them lived beyond the age of 40. Therefore, Charles 00:15:14.406 --> 00:15:20.997 Darwin also turned 40 on February twelve, 1849. Now the argument looks pretty good. 00:15:20.997 --> 00:15:26.576 We had to have two suppressed premises but we finally have a valid argument. And what 00:15:26.576 --> 00:15:31.301 this shows is that sometimes the suppressed premises are purely factual 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 00:15:36.683 --> 00:15:42.077 beyond 40. So sometimes we have factual suppressed premises. Here's another quick 00:15:42.077 --> 00:15:46.952 example. You ought to obey her because she's your mother. Here, the premise is 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 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 00:15:57.870 --> 00:16:03.020 false that you ought to obey her. When could that happen? Maybe, she was like 00:16:03.020 --> 00:16:08.933 abusive or stupid or whatever. Then maybe you ought not to obey her even though she 00:16:08.933 --> 00:16:14.241 is your mother. So we have to add a premise, namely, you ought to obey your 00:16:14.241 --> 00:16:19.244 mother. Now we can say she's your mother, you ought to obey your mother therefore 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 00:16:24.540 --> 00:16:29.219 mother is questionable because maybe she was abusive or stupid. So let's add 00:16:29.219 --> 00:16:34.268 another supressed premise that your mother was not abusive or stupid, of course we a 00:16:34.268 --> 00:16:39.071 lso have to qualify that moral premise that you ought to obey your mother if 00:16:39.071 --> 00:16:43.812 she's not abusive or stupid. And now the argument looks like this - she's your 00:16:43.812 --> 00:16:48.900 mother, you ought to obey your mother if she's not abusive or stupid. Your mother 00:16:48.900 --> 00:16:54.880 was not abusive or stupid. Therefore, you ought to obey her. An notice that here, we 00:16:54.880 --> 00:17:00.409 added a moral premise about the fact that you ought to obey your mother under 00:17:00.409 --> 00:17:05.867 certain conditions. Namely, she's not abusive or stupid. And the second premise 00:17:05.867 --> 00:17:11.042 is she was not abusive or stupid. So, we have a moral premise and a factual 00:17:11.042 --> 00:17:16.216 premise, both being suppressed in the argument that you ought to obey her 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 00:17:22.633 --> 00:17:28.521 synagogue. Well, that's clearly not valid. One suppressed premise is that you're 00:17:28.521 --> 00:17:34.291 Jewish. The other suppressed premise is you haven't been to synagogue already 00:17:34.291 --> 00:17:39.906 today, on this Sabbath. And the third suppressed premise is a religious norm, 00:17:39.906 --> 00:17:45.735 mainly Jews ought to go to the synagogue on the Sabbath. And you need that whole 00:17:45.735 --> 00:17:50.912 bunch of suppressed premises in order to get from the premise, that it's the 00:17:50.912 --> 00:17:56.339 Sabbath, to the conclusion, that you ought to go to synagogue. And of course all of 00:17:56.339 --> 00:18:01.504 those premises might be questionable. Some people would question them. Some people 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 00:18:06.910 --> 00:18:11.814 who gave the original argument. And anybody who says it's the Sabbath, so you 00:18:11.814 --> 00:18:16.203 ought to go to synagogue, seems to be assuming you're Jewish, you haven't been 00:18:16.203 --> 00:18:21.152 already, and Jews ought to go to the synagogue on the Sabbath. So what these 00:18:21.152 --> 00:18:26.938 suppressed premises do is they bring out the assumptions that somebody who gave 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 00:18:32.869 --> 00:18:38.800 to do with linguistic suppressed premises. Jen and Bob are first cousins, therefore 00:18:38.800 --> 00:18:47.470 they share a grandparent. Now, in order to understand that argument, you have to know 00:18:47.470 --> 00:18:52.162 that first cousins always share a grandparent. That just follows from the 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 00:18:58.847 --> 00:19:04.002 biological sisters are female. And so, there's even more need to bring out that 00:19:04.002 --> 00:19:09.356 linguistics suppressed premise in this case. But it's still not necessary to make 00:19:09.356 --> 00:19:14.843 the argument valid. It's just not possible that Janet and Bob are first cousins, and 00:19:14.843 --> 00:19:19.602 they don't share a grandparent. Because the suppressed premise is purely 00:19:19.602 --> 00:19:24.663 linguistic, so it's necessarily true, so you can't possibly be first cousins 00:19:24.663 --> 00:19:29.700 without sharing a grandparent. Still, the point of bringing out linguistic 00:19:29.700 --> 00:19:34.944 suppressed premises is to show every little step along the way. The argument 00:19:34.944 --> 00:19:39.952 might be valid without those suppressed linguistic premises, but we won't 00:19:39.952 --> 00:19:45.153 understand why it's valid and why the reasoning goes through unless we add the 00:19:45.153 --> 00:19:51.412 linguistics suppressed premise. So it's worth doing that. Shh. Here's a trick. 00:19:51.412 --> 00:20:00.400 Don't tell anybody. Okay? It's just between me and you. You can always make 00:20:00.400 --> 00:20:06.916 any argument valid just by adding a suppressed premise that says if the 00:20:06.916 --> 00:20:14.069 premises are true, then the conclusion is true. But don't tell anybody, because if 00:20:14.069 --> 00:20:19.991 people start doing that, and they start making the argument valid that way, with 00:20:19.991 --> 00:20:26.270 that suppressed premise, we're never going to understand the pathway of reasoning. It 00:20:26.270 --> 00:20:31.095 makes the argument valid, but it doesn't serve the real purpose of adding 00:20:31.578 --> 00:20:37.231 suppressed premises which is to understand the pathway of reasoning. So you can do 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 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 00:20:48.330 --> 00:20:54.604 valid so that we can understand the pathway of reasoning. So it's important to 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 00:21:02.339 --> 00:21:07.850 pretty trivial, I admit it. But the same points apply in very important context 00:21:07.850 --> 00:21:13.573 such as politic debates, politician can suppress premises in perfectly legitimate 00:21:13.573 --> 00:21:19.508 ways. They're just trying to save time and make their arguments more efficient, maybe 00:21:19.508 --> 00:21:25.615 even sometimes clearer because you don't have to add all those little details. But 00:21:25.615 --> 00:21:31.684 sometimes politicia ns abuse suppressed premises. They take things for granted 00:21:31.684 --> 00:21:37.910 that they shouldn't be taking for granted. Here's an example. A politician might 00:21:37.910 --> 00:21:43.980 argue, my opponent is soft on crime because he's opposed to the death penalty. 00:21:44.300 --> 00:21:50.016 Well, that assumes, as a suppressed premise, that anyone who's opposed to the 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 00:21:56.143 --> 00:22:01.460 that, it would seem pretty questionable, and that's probably why he suppresses it. 00:22:01.720 --> 00:22:07.446 And then another politician might say, my opponent is in favor of the death penalty, 00:22:07.446 --> 00:22:13.034 so he must not have read all the recent studies that show that the death penalty 00:22:13.034 --> 00:22:18.977 doesn't deter. Well that argument assumes the suppressed premise that if you've read 00:22:18.977 --> 00:22:23.556 those studies you'ld be convinced by them, and that the only point of the death 00:22:23.556 --> 00:22:29.642 penalty is deterrence. But the point is that politicians talking about extremely 00:22:29.642 --> 00:22:34.047 important issues can take things for granted, that if they were brought into 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 00:22:38.858 --> 00:22:43.500 listening to people give arguments on important issues in your life, then you 00:22:43.500 --> 00:22:49.802 ought to be looking for these suppressed premises and asking yourself whether or 00:22:49.802 --> 00:22:55.949 not you really ought to be agreeing with them about that assumption. Finally, we 00:22:55.949 --> 00:23:01.628 finished reconstruction. Yipee, right? Oh, no, not quite, because there's one more 00:23:01.628 --> 00:23:06.951 stage, and that stage is drawing a conclusion. Of course, if we've come up 00:23:06.951 --> 00:23:12.349 with a sound reconstruction, then we know that the argument is sound, and we know 00:23:12.349 --> 00:23:18.817 that the conclusion is true, because every sound argument has a true conclusion. But 00:23:18.817 --> 00:23:23.519 if we don't come up with a sound reconstruction, then what do we say? Well, 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 00:23:28.415 --> 00:23:33.117 we couldn't come up with a sound reconstruction because there just is no 00:23:33.117 --> 00:23:37.240 sound reconstruction. But maybe we couldn't come up with a sound 00:23:37.240 --> 00:23:42.200 reconstruction because we just weren't imaginative enough, or try hard enough. 00:23:42.200 --> 00:23:47.592 Still, if we try really long an hard, and charitably interpret the a rgument as best 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, 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 00:23:58.312 --> 00:24:03.573 doesn't mean that the conclusion's not true, because unsound arguments can still 00:24:03.573 --> 00:24:09.107 have true conclusions. But at least we know that this argument doesn't prove that 00:24:09.107 --> 00:24:14.094 the conclusion is true. And so, this method of reconstruction can lead us 00:24:14.094 --> 00:24:19.290 either to the belief that the argument is sound, because we found the sound 00:24:19.290 --> 00:24:24.831 reconstruction, or to the conclusion is not sound, because we tried long and hard 00:24:24.831 --> 00:24:30.234 to find a sound reconstruction that didn't, but that's still not going to show 00:24:30.234 --> 00:24:36.546 us that the conclusion of the argument is false. The point of reconstruction then is 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 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 00:24:48.007 --> 00:24:51.120 believing that the argument is sound or not.