1 00:00:02,660 --> 00:00:07,777 Now we've learned how to identify an argument and put it in standard form. 2 00:00:07,777 --> 00:00:13,447 We've also learned from the definition of argument, that the premises are intended 3 00:00:13,447 --> 00:00:16,144 to be reasons for the conclusion. Great. 4 00:00:16,144 --> 00:00:19,118 Intended to be a reason for the conclusion. 5 00:00:19,118 --> 00:00:22,368 Well intentions are nice, but success is better. 6 00:00:22,368 --> 00:00:27,831 What we need to figure out is when the person succeeds in giving premises that 7 00:00:27,831 --> 00:00:33,156 really are reasons for the conclusion. For simplicity, let's focus on argument 8 00:00:33,156 --> 00:00:38,933 whose purpose is justification. Then the question is, do the premises 9 00:00:38,933 --> 00:00:46,210 justify you in believing the conclusion? Well, imagine that you don't know whether 10 00:00:46,210 --> 00:00:50,898 there's any life on Mars. You have no evidence one way or the 11 00:00:50,898 --> 00:00:54,823 other. Then you ask a friend and the friend says 12 00:00:54,823 --> 00:00:58,588 ha, I know there's life on Mars. I can prove it to you. 13 00:00:58,588 --> 00:01:02,780 Here, this argument will show you that there's life on Mars. 14 00:01:02,780 --> 00:01:08,436 There is at least one bacterium on Mars. Therefore there is life on Mars. 15 00:01:08,436 --> 00:01:14,092 Now notice that if the premise is true the conclusion has got to be true. 16 00:01:14,092 --> 00:01:20,613 And if you and your friend are justified in believing the premise then you and you 17 00:01:20,613 --> 00:01:25,170 are friend are also justified in believing the conclusion. 18 00:01:25,170 --> 00:01:30,699 So this argument looks pretty good so far but of course you have to ask your 19 00:01:30,699 --> 00:01:35,870 friend, well how do you know that there's at least one bacterium on Mars? 20 00:01:35,870 --> 00:01:40,600 And suppose your friend says, well I'm just guessing. 21 00:01:40,600 --> 00:01:45,425 Then the argument is clearly no good. If there's no reason to believe the 22 00:01:45,425 --> 00:01:50,316 premise because your friend is just guessing then you're not justified in 23 00:01:50,316 --> 00:01:54,546 believing that premise. And if you're not justified in believing 24 00:01:54,546 --> 00:01:59,437 the premise then how can that premise make you justified in believing the 25 00:01:59,437 --> 00:02:02,940 conclusion. More generally an argument cannot justify 26 00:02:02,940 --> 00:02:07,831 you in believing the conclusion unless you are justified in accepting the 27 00:02:07,831 --> 00:02:12,350 premises of that argument. Now, suppose your friends says oh, but I 28 00:02:12,350 --> 00:02:17,950 do have a reason for the premise I do then we have to ask what kind of reason 29 00:02:17,950 --> 00:02:21,181 is it? And, at that point your friend needs to 30 00:02:21,181 --> 00:02:24,412 express reason. And, how do we express reasons? 31 00:02:24,412 --> 00:02:27,859 In arguments. So, your friend has to give another 32 00:02:27,859 --> 00:02:32,526 argument for the premise. Where the premise of the first argument 33 00:02:32,526 --> 00:02:38,065 is the conclusion of the second argument. Wait a minute, we got a problem. 34 00:02:38,065 --> 00:02:42,797 Because that second argument is itself going to have premises. 35 00:02:42,797 --> 00:02:46,461 And you have to be justified in believing those. 36 00:02:46,461 --> 00:02:52,263 So the premises of the second argument have to be the conclusion of a third 37 00:02:52,263 --> 00:02:55,148 argument. And so on and so on because the third 38 00:02:55,148 --> 00:02:58,041 argument needs premises. They have to be justified. 39 00:02:58,041 --> 00:03:01,165 So they have to be the conclusion of another argument. 40 00:03:01,165 --> 00:03:05,273 Which also has to have premises. And those have to be the conclusion of 41 00:03:05,273 --> 00:03:07,414 another argument. And so on and so on. 42 00:03:07,414 --> 00:03:09,960 It looks like we've got a real problem here. 43 00:03:09,960 --> 00:03:14,831 In order for the premises to be justified they have to be backed up by an argument, 44 00:03:14,831 --> 00:03:19,410 but the argument has premises of its own that have to be backed up by another 45 00:03:19,410 --> 00:03:23,577 argument and so on, and so on. This problem is called the problem of the 46 00:03:23,577 --> 00:03:28,214 skeptical regress because you regress back to one argument after another, after 47 00:03:28,214 --> 00:03:31,971 another, after another, after another, after another, after another. 48 00:03:31,971 --> 00:03:36,080 And it's hard to see how that regress, is ever, going to come to an end. 49 00:03:36,080 --> 00:03:40,573 There seem to be only three ways to get around this skeptical regress. 50 00:03:40,573 --> 00:03:44,168 The first is to start with a premise that's unjustified. 51 00:03:44,168 --> 00:03:48,470 If it's unjustified, then it doesn't need an argument to back it up. 52 00:03:48,470 --> 00:03:52,667 And that means that you're not going to have this chain of arguments going back 53 00:03:52,667 --> 00:03:55,800 and back and back and back and back and back and back. 54 00:03:55,800 --> 00:04:00,446 The second possibility is to have a structure where the arguments move in a 55 00:04:00,446 --> 00:04:03,320 circle. One claim is justified by another which 56 00:04:03,320 --> 00:04:07,783 is justified by another which is justified by another which is justified 57 00:04:07,783 --> 00:04:11,400 by the first claim. And they just move in a circle. 58 00:04:11,400 --> 00:04:16,229 The third possibility, is that the chain of arguments goes back infinitely. 59 00:04:16,229 --> 00:04:19,754 It never stops. Every claim has an argument to back it 60 00:04:19,754 --> 00:04:22,495 up. And there's no end, so you never have a 61 00:04:22,495 --> 00:04:27,130 prentice which doesn't have an argue to back it up, because it's infinite. 62 00:04:27,130 --> 00:04:31,989 Those seem to be the three main options here to avoid the skeptical regress. 63 00:04:31,989 --> 00:04:36,658 The first possibility then, is to start with a premise that's unjustified. 64 00:04:36,658 --> 00:04:41,965 And that seems pretty neat if you can get away with it but we already saw why that 65 00:04:41,965 --> 00:04:45,226 won't work. We saw your friend arguing that there's 66 00:04:45,226 --> 00:04:50,086 life on Mars because there's at least one bacterium on Mars, and he was just 67 00:04:50,086 --> 00:04:53,156 guessing. If you just guess at your premises, you 68 00:04:53,156 --> 00:04:57,248 have no reason to believe them. Then, an argument that uses those 69 00:04:57,248 --> 00:05:00,830 premises cannot justify you in believing the conclusion. 70 00:05:00,830 --> 00:05:04,570 But in addition, just think about it this way. 71 00:05:04,570 --> 00:05:09,491 You could prove anything if we let you start with unjustified premises. 72 00:05:09,491 --> 00:05:15,106 If you can just make up your premises for no reason then there's no stopping you 73 00:05:15,106 --> 00:05:19,681 from believing whatever, including things that are obviously false. 74 00:05:19,681 --> 00:05:25,019 So it seems to be a real problem to start with premises that are unjustified. 75 00:05:25,019 --> 00:05:30,356 Next, the second way to respond to the skeptical regress is to use a circular 76 00:05:30,356 --> 00:05:33,518 structure. and it's kind of neat, if you think about 77 00:05:33,518 --> 00:05:37,501 it, because, if you want to prove one claim, you prove it on the basis of 78 00:05:37,501 --> 00:05:40,531 another claim. And then you prove that second claim on 79 00:05:40,531 --> 00:05:45,132 the basis of the third, and the third on the basis of the fourth and the fourth on 80 00:05:45,132 --> 00:05:47,937 the fifth, and the fifth on the basis of the first. 81 00:05:47,937 --> 00:05:51,528 And now you've got this circle, and the arguments go in a circle. 82 00:05:51,528 --> 00:05:55,118 But that means that every premise has an argument to back it up. 83 00:05:55,118 --> 00:05:58,380 Cause you can keep going around the circle forever. 84 00:05:58,380 --> 00:06:03,050 You can think about it a little bit, it'll be obvious that that's no good. 85 00:06:03,050 --> 00:06:07,210 And that can be shown by looking at the smallest circle there is. 86 00:06:07,210 --> 00:06:10,949 So suppose your friend says, I can prove there's life on Mars. 87 00:06:10,949 --> 00:06:14,505 Here's my argument. There's life on Mars, therefore there's 88 00:06:14,505 --> 00:06:16,712 life on Mars. Clearly, that's no good. 89 00:06:16,712 --> 00:06:21,678 And the reason why it's no good is that if he didn't know whether there was life 90 00:06:21,678 --> 00:06:25,909 on Mars to begin with, you wouldn't know whether the premise was true. 91 00:06:25,909 --> 00:06:30,445 because if you don't know the conclusion you can't know the premise, since the 92 00:06:30,445 --> 00:06:34,240 premise is the conclusion. So if you're not justified in believing 93 00:06:34,240 --> 00:06:38,365 the conclusion to begin with, you're not justified in believing the premise. 94 00:06:38,365 --> 00:06:41,885 And that means that the argument didn't really get you anywhere. 95 00:06:41,885 --> 00:06:46,553 It just ends up where it started. And in addition, it has the same problem 96 00:06:46,553 --> 00:06:50,833 we saw in the first approach involving unjustified premises. 97 00:06:50,833 --> 00:06:54,900 Because you can use circular arguments to prove anything. 98 00:06:54,900 --> 00:06:59,428 You can prove there's life on Mars there's life on Mars therefore there's 99 00:06:59,428 --> 00:07:02,548 life on Mars. You can prove there's no life on Mars 100 00:07:02,548 --> 00:07:06,954 therefore there's no life on Mars. You can do it either way and the fact 101 00:07:06,954 --> 00:07:11,604 that an argument can be used either way to prove either conclusion suggests 102 00:07:11,604 --> 00:07:14,602 there's a big problem with that kind of argument. 103 00:07:14,602 --> 00:07:19,620 So now we are down to the third and final way to get around the skeptical regress, 104 00:07:19,620 --> 00:07:23,060 and that is to use an infinite chain of arguments. 105 00:07:23,060 --> 00:07:28,366 If you think about it, in a concrete case, you'll see why that's a problem as 106 00:07:28,366 --> 00:07:31,578 well. Suppose your friend says there's life on 107 00:07:31,578 --> 00:07:35,628 Mars and I can prove it. And you say fine, give me a reason? 108 00:07:35,628 --> 00:07:40,795 Well there's a least one bacterium on Mars, therefore there's life on Mars. 109 00:07:40,795 --> 00:07:46,311 And you go okay, fine but how do you know there's a least one bacterium on Mars? 110 00:07:46,311 --> 00:07:51,548 I've got another argument he says, there are at least two bacterium on Mars, 111 00:07:51,548 --> 00:07:54,970 therefore there's at least one bacterium on Mars. 112 00:07:54,970 --> 00:07:59,877 But how do you know there's at least two? Well, there are at least three bacteria 113 00:07:59,877 --> 00:08:02,240 on Mars. Therefore, there are at least two 114 00:08:02,240 --> 00:08:05,086 bacteria on Mars. But how do you know there are at least 115 00:08:05,086 --> 00:08:07,192 three? Well, there are at least four so there 116 00:08:07,192 --> 00:08:09,920 are at least three. Well, there are at least five so there 117 00:08:09,920 --> 00:08:12,744 are at least four. Well, there are at least six so there are 118 00:08:12,744 --> 00:08:14,850 at least five. And so on and so on and so on. 119 00:08:14,850 --> 00:08:17,770 You could go on infinitely. So an infinite chain of arguments. 120 00:08:17,770 --> 00:08:23,014 Would allow you to prove that there's life on Mars even if you have no evidence 121 00:08:23,014 --> 00:08:27,997 whatsoever of any bacteria because you're going to have an argument but if the 122 00:08:27,997 --> 00:08:33,308 premise that you are arguing from doesn't have an independent justification then 123 00:08:33,308 --> 00:08:38,422 the infinite chain is going to be no good at all in justifying the conclusion of 124 00:08:38,422 --> 00:08:43,520 that argument. So many people see this skeptical regress 125 00:08:43,520 --> 00:08:47,560 as a deep and serious philosophical issue. 126 00:08:47,560 --> 00:08:52,804 If the unjustified premise approach doesn't work, and the circular argument 127 00:08:52,804 --> 00:08:58,189 structure doesn't work, and the infinite chain of arguments doesn't work, then 128 00:08:58,189 --> 00:09:01,755 it's hard to see how we can get around the problem. 129 00:09:01,755 --> 00:09:07,559 Which is to say, it's hard to see how any kind of argument could ever justify us in 130 00:09:07,559 --> 00:09:11,825 believing anything. Philosophers really scratched their heads 131 00:09:11,825 --> 00:09:15,041 about that for a long time. And worry about it. 132 00:09:15,041 --> 00:09:19,962 It keeps them up at night. But we're going to have look at how 133 00:09:19,962 --> 00:09:24,501 practical people solve a similar problem in everyday life. 134 00:09:24,501 --> 00:09:30,370 So how we solve this skeptical regress problem in everyday life well there 135 00:09:30,370 --> 00:09:35,848 various tricks which you can use. For example, one way is to just start 136 00:09:35,848 --> 00:09:42,662 from assumptions that everybody shares. So if I say, well you really ought to buy 137 00:09:42,662 --> 00:09:46,760 a Honda because Hondas are very reliable cars. 138 00:09:46,760 --> 00:09:49,877 Then I'm assuming that you want your car to be reliable. 139 00:09:49,877 --> 00:09:53,550 You don't like to have to take it in to the mechanic all the time. 140 00:09:53,550 --> 00:09:56,620 You don't want it to break down on the road. 141 00:09:56,620 --> 00:10:01,601 And if you want reliability and I want reliability, then we can start from the 142 00:10:01,601 --> 00:10:06,518 assumption that reliability's a good thing and that that's a reason to buy a 143 00:10:06,518 --> 00:10:11,467 car that is reliable. But of course you might say, well but our 144 00:10:11,467 --> 00:10:14,940 Honda's reliable. And then I might. 145 00:10:14,940 --> 00:10:18,399 Appeal to an authority. Well, it's obvious that they are. 146 00:10:18,399 --> 00:10:22,802 Or, Consumer Reports has done a study that shows that they're reliable. 147 00:10:22,802 --> 00:10:27,897 And I can appeal to an authority, and if you accept that authority, go, Consumer 148 00:10:27,897 --> 00:10:31,419 Reports, we can trust them, then, my argument's going to work. 149 00:10:31,419 --> 00:10:36,136 You're going to have a reason to believe the conclusion, and it might persuade 150 00:10:36,136 --> 00:10:39,155 you, and make you come to believe the conclusion. 151 00:10:39,155 --> 00:10:42,489 But, suppose that someone is going to raise an objection. 152 00:10:42,489 --> 00:10:45,823 They say, well, Consumer Reports has been wrong before. 153 00:10:45,823 --> 00:10:50,093 They might be wrong this time. Well, then, I need to discount that 154 00:10:50,093 --> 00:10:53,387 objection. I need to respond to it, and say, well, 155 00:10:53,387 --> 00:10:58,925 maybe they have been wrong sometimes, but this time, you know, they've got a good 156 00:10:58,925 --> 00:11:04,183 study and it was careful, or whatever. And the but means, I'm discounting the 157 00:11:04,183 --> 00:11:09,700 objection that you have raised, and I might even discount it in advance. 158 00:11:09,700 --> 00:11:14,660 Well I might just guard my client I might say, well. 159 00:11:14,660 --> 00:11:18,454 They might be right, in this case. Or they're probably right, without 160 00:11:18,454 --> 00:11:23,142 claiming that they definitely are right. So I can assure you by signing as some 161 00:11:23,142 --> 00:11:26,869 kind of authority. I can discount objections and I can guard 162 00:11:26,869 --> 00:11:29,788 my premises by saying, well it's probably right. 163 00:11:29,788 --> 00:11:32,583 Instead of saying that it's definitely right. 164 00:11:32,583 --> 00:11:37,278 And those are three ways of solving. The skeptical regress problem in everyday 165 00:11:37,278 --> 00:11:41,786 life that we're going to look at in much more detail in the next three lectures. 166 00:11:41,786 --> 00:11:44,830 But the point of this lecture has been more general. 167 00:11:44,830 --> 00:11:48,927 In order to solve the skeptical regress problem, you have to find some 168 00:11:48,927 --> 00:11:51,562 assumptions that you and your audience share. 169 00:11:51,562 --> 00:11:55,249 They might be assumptions about the premises of your arguments. 170 00:11:55,249 --> 00:11:59,523 They might be assumptions about authorities that supposedly support your 171 00:11:59,523 --> 00:12:02,860 premises and that they accept as authorities or whatever. 172 00:12:02,860 --> 00:12:06,708 But there have to be some assumptions that you share with your audience in 173 00:12:06,708 --> 00:12:10,557 order to get the argument going. And that's kind of tricky because it's 174 00:12:10,557 --> 00:12:15,099 going to depend on the context. If you are dealing with an audience that 175 00:12:15,099 --> 00:12:20,020 shares a lot of your assumptions that argument is going to be relatively easy. 176 00:12:20,020 --> 00:12:24,499 But if you are dealing with an audience that doesn't share any of your 177 00:12:24,499 --> 00:12:29,104 assumptions it's going to be impossible. And, in areas where there's a lot of 178 00:12:29,104 --> 00:12:34,403 disagreement it's going to be hard to get your argument going because your premises 179 00:12:34,403 --> 00:12:39,450 are going to be questioned and denied or rejected by the people in the audience. 180 00:12:39,450 --> 00:12:43,791 So, what these tricks do, is they give you ways to get the argument going. 181 00:12:43,791 --> 00:12:46,264 But they're not going to work in every case. 182 00:12:46,264 --> 00:12:51,148 And we'll have to look at that, as we're looking at these three different ways to 183 00:12:51,148 --> 00:12:54,948 solve the skeptical regress problem in the next three lectures.