0:00:02.560,0:00:10.655
It's been a long and winding road as the[br]Beatles used to say, but we're finally at

0:00:10.655,0:00:17.266
the last stages of reconstructing[br]arguments. We've looked at stage one,

0:00:17.266,0:00:24.241
which is close analysis. Stage two which[br]is get down to basics. Stage three which

0:00:24.241,0:00:31.215
is sharpen edges, stage four is organize[br]parts, and we are doing stage five which

0:00:31.215,0:00:37.651
is fill in gaps and we'll also get to[br]stage six which is conclude. Stage five

0:00:37.651,0:00:42.609
really consists of four separate steps.[br]First we need to assess the argument for

0:00:42.609,0:00:47.628
validity. Then we need to add suppressed[br]premises. Enough of them to make it valid.

0:00:47.628,0:00:52.693
Then we need to assess those suppressed[br]premises for truth or falsehood. And then

0:00:52.693,0:00:58.390
we need to qualify the suppressed premises[br]in order to make them true. The whole goal

0:00:58.390,0:01:03.753
is to make the suppressed premises both[br]plausible for their truth, and enough to

0:01:03.753,0:01:09.182
make the argument valid. So, these steps[br]within the stage really do work in tandem

0:01:09.182,0:01:14.276
together to try and make the argument[br]good. We already learned how to assess

0:01:14.276,0:01:18.874
validity. You simply ask, "Is it possible[br]for the premises to be true and the

0:01:18.874,0:01:23.715
conclusion false, and if so, the argument[br]is not valid and if not, the argument is

0:01:23.715,0:01:28.677
valid." And the way you figure out whether[br]it's possible is you try to tell a story

0:01:28.677,0:01:33.458
or describe a situation and if you can[br]describe a coherent situation where the

0:01:33.458,0:01:38.420
premises are true and the conclusion is[br]false, then that show that the argument is

0:01:38.420,0:01:43.262
not really valid. The main topic for today[br]is, what do you do when you assess the

0:01:43.262,0:01:48.145
argument for validity and you find out[br]it's not valid?" And the answer is, you

0:01:48.145,0:01:53.929
add suppressed premises, enough of them to[br]make the argument valid. But that might

0:01:53.929,0:01:58.874
seem like cheating. I mean, you start with[br]an argument that's no good, it's not

0:01:58.874,0:02:03.820
valid, and then you just throw in some[br]extra premises in order to make it valid.

0:02:03.820,0:02:08.752
Why is it that's just distorting the[br]argument and making up something that

0:02:08.752,0:02:14.014
wasn't there? The answer is that it's not[br]really bad. And if it were bad, we'd all

0:02:14.014,0:02:19.210
be in bad shape because in everyday life,[br]people always take things for granted.

0:02:19.210,0:02:24.406
They make assumptions. We do it too, and[br]if we didn't, boy, our arguments would be

0:02:24.406,0:02:28.813
really long and boring. So there's[br]something to be said in favor of

0:02:28.813,0:02:33.680
suppressing premises, at least, the[br]obvious ones that people really do take

0:02:33.680,0:02:39.520
for granted. But we can also get tricked.[br]People can suppress premises that really

0:02:39.520,0:02:45.156
are questionable, and they just don't want[br]us to see that they're making that

0:02:45.156,0:02:50.623
assumption. So, it's useful to fill out[br]the argument with suppressed premises to

0:02:50.623,0:02:55.762
make sure it really is valid, because that[br]brings those assumptions out in the open,

0:02:55.762,0:03:00.900
where we can assess whether or not they're[br]true or false. Another reason to fill in

0:03:00.900,0:03:05.576
suppressed premises is to understand the[br]argument better. Because if people

0:03:05.576,0:03:10.798
suppress premises, then they're showing us[br]some of their footprints along the path.

0:03:10.798,0:03:15.893
But if we really want to know the full[br]path that their reasoning followed, we've

0:03:15.893,0:03:20.684
got to see every single footprint. So, the[br]goal of bringing up the suppressed

0:03:20.684,0:03:25.927
premises is to let us trace exactly where[br]the reasoning is from one step to another.

0:03:25.927,0:03:30.796
So there are two goals: One is to trace[br]the full path every step and the other

0:03:30.796,0:03:36.040
goal is to see if there are any miss-steps[br]or they are trying to hid something from

0:03:36.040,0:03:40.784
us by getting rid of one of their[br]footsteps, so that's the point of bringing

0:03:40.784,0:03:45.900
up suppressed premises. To accomplish[br]these goals is tricky. You have to find

0:03:45.900,0:03:51.225
suppressed premises that are just strong[br]enough to make the argument valid but not

0:03:51.225,0:03:56.550
so strong that there gonna be implausible.[br]Cuz you don't wanna ascribe all kinds of

0:03:56.550,0:04:01.362
suppressed premises to the person that[br]they didn't really believe, and they

0:04:01.362,0:04:06.751
didn't really need for their argument. So[br]it's kind of like Goldilocks and the Three

0:04:06.751,0:04:11.820
Bears. You want suppressed premises to be[br]not too hot and not too cold, but just

0:04:11.820,0:04:17.754
right. Here's an example from a previous[br]lecture. My wife always gives me either a

0:04:17.754,0:04:24.156
sweater or a board game. This box does not[br]contain a sweater because it rattles when

0:04:24.156,0:04:29.947
it's shaken so this time she must have[br]given me a board game. We put this in

0:04:29.947,0:04:35.967
standard form this way. First premise:[br]This box rattles wh en I shake it and that

0:04:35.967,0:04:42.853
shows you it doesn't contain a sweater.[br]Third, she always gives me either a

0:04:42.853,0:04:49.180
sweater or a board game. Conclusion, this[br]time she must have given me a board game.

0:04:50.220,0:04:56.584
Now the first step in this argument is,[br]this box rattles when I shake it. And the

0:04:56.584,0:05:02.649
conclusion there is it doesn't contain a[br]sweater. That's the part of the argument

0:05:02.649,0:05:08.640
we want to focus on here and ask whether[br]that argument is valid. The argument is

0:05:08.640,0:05:14.480
not valid, because it's possible for the[br]premise to be true and the conclusion

0:05:14.480,0:05:19.674
false. How can that happen? Well, my wife[br]might be fooling me. She might know that I

0:05:19.674,0:05:24.861
expect either a sweater or a board game,[br]so she puts a sweater in the box. And then

0:05:24.861,0:05:29.921
she puts little rocks around the outside[br]so when I shake it, I'll hear something.

0:05:29.921,0:05:35.040
So that's possible, and that shows that[br]the argument's not valid. Well, how can we

0:05:35.040,0:05:40.529
make the argument valid? The question here[br]is, can we add a suppressed premise that

0:05:40.529,0:05:45.750
will turn this invalid argument into a[br]valid argument? Here's one that will do

0:05:45.750,0:05:51.792
the trick. A box that contains a sweater[br]doesn't rattle when shaken. Now the

0:05:51.792,0:05:57.556
argument looks like this. This box rattles[br]when I shake it. The box that contains a

0:05:57.556,0:06:02.969
sweater doesn't rattle when shaken, so[br]this box doesn't contain a sweater. The

0:06:02.969,0:06:08.874
explicit premise is that this box rattles[br]when I shake it. The suppressed premise is

0:06:08.874,0:06:14.779
that a box that contains a sweater doesn't[br]rattle when shaken and together they are

0:06:14.779,0:06:20.614
suppose support the conclusion that this[br]box doesn't contain a sweater, but do they

0:06:20.614,0:06:26.521
really support that conclusion? Is the[br]argument valid? Well, it's valid only if

0:06:26.521,0:06:31.275
there's no possibility that the premises[br]are true and the conclusions false.

0:06:31.275,0:06:36.468
Without the suppressed premise we saw this[br]might be possible, because my wife might

0:06:36.468,0:06:41.097
be fooling me and putting rocks around the[br]sweater. So let's see if that's going to

0:06:41.472,0:06:45.972
ruin the validity of this argument. No![br]Because if the sweater has got rocks

0:06:45.972,0:06:51.090
around it so it makes noise when I shake[br]it, then the premise that says a box that

0:06:51.090,0:06:55.331
contains a sweater doesn't rattle when[br]shaken turns out to be fal se.

0:06:55.335,0:07:00.641
So that's not a case where the premises[br]are true and the conclusions false because

0:07:00.641,0:07:05.759
the premise is false in that case. So, by[br]adding this premise, we actually succeeded

0:07:05.759,0:07:11.866
in making the argument valid. The problem[br]of course is that validity is not enough

0:07:11.866,0:07:17.843
for a good argument, as we saw several[br]lectures ago. You can have an argument

0:07:17.843,0:07:23.742
that's very bad, when the argument is not[br]sound. What we want really is soundness.

0:07:23.742,0:07:29.347
So, that's why we need the next step,[br]mainly, check the supressed premises for

0:07:29.347,0:07:34.951
truth. Assess whether they're true or[br]false. And, if they're not true, then you

0:07:34.951,0:07:40.850
need to qualify them, in order to make[br]them true. Cuz you don't want to claim

0:07:40.850,0:07:46.750
that the person giving the argument was[br]assuming this falsehood, when the didn't

0:07:46.750,0:07:52.706
have to. So let's see if there's some way[br]to qualify this suppressed premise in

0:07:52.706,0:08:00.037
order to make it true. How can we qualify[br]this premise to make it true? How are we

0:08:00.037,0:08:06.833
going to do that? Let me think. Oh. What[br]about that little word only. You could add

0:08:06.833,0:08:15.020
that. You could say, a box that contains[br]only a sweater doesn't rattle when shaken.

0:08:15.620,0:08:20.919
But the word only, what exactly does that[br]mean? We need to clarify that. What

0:08:20.919,0:08:26.430
exactly is the word only exclude? It[br]excludes something, that's the function of

0:08:26.430,0:08:32.684
the word only, but what does it exclude?[br]Well. It probably excludes other things

0:08:32.684,0:08:38.918
that might make the rattling sound like if[br]my wife put rocks in the box. So we can

0:08:38.918,0:08:45.228
clarify this premise by saying a box that[br]contains only a sweater and not anything

0:08:45.228,0:08:51.524
else that might make a rattling sound when[br]shaken, won't rattle when shaken. Well, is

0:08:51.524,0:08:57.538
that premise true? Well, you might quibble[br]about details but it's close enough for

0:08:57.538,0:09:03.330
now. What we need to do though is to go[br]back and determine whether, when we put

0:09:03.330,0:09:09.270
that suppressed premise in, the argument's[br]valid. And the argument now looks like

0:09:09.270,0:09:15.285
this. This box does rattle when shaken,[br]and a box doesn't rattle when shaken if it

0:09:15.285,0:09:21.769
contains only a sweater and not anything[br]else that makes a rattling sound. So this

0:09:21.769,0:09:29.492
box doesn't contain a sweater. Is that[br]valid? Well, no, for the same reason we s

0:09:29.492,0:09:35.456
aw before, because my wife might be a[br]trickster who puts rocks around my sweater

0:09:35.456,0:09:41.580
in the birthday present box in order to[br]fool me. Then, the premises can be true,

0:09:41.580,0:09:48.401
and the conclusion false. It's possible[br]that, the first premise is true. This box

0:09:48.401,0:09:54.907
rattles when I shake it. And the second[br]premise is true, a box doesn't rattle when

0:09:54.907,0:10:00.450
shaken if it contains only a sweater and[br]nothing else that makes a rattling sound.

0:10:00.450,0:10:04.799
But it's false that this box doesn't[br]contain a sweater, cuz it still does

0:10:04.799,0:10:09.446
contain a sweater, and it contains a[br]sweater in addition to those pesky little

0:10:09.446,0:10:13.744
rocks that make all that rattling noise.[br]Well, if your argument's not valid, we've

0:10:13.744,0:10:18.038
got to go back to that other step and add[br]another suppressed premise. Remember how I

0:10:18.038,0:10:22.281
told you how these different steps within[br]this stage work in tandem and what's

0:10:22.281,0:10:25.903
happening is you've got to check it for[br]validity, add a suppressed premise,

0:10:25.903,0:10:30.042
recheck for validity, maybe add another[br]suppressed premise, and that's what we're

0:10:30.042,0:10:35.232
doing now. So what kind of suppressed[br]premised can we add. Well, we could add my

0:10:35.232,0:10:40.867
wife is not a trickster but basically that[br]amounts to she wouldn't put rocks in a

0:10:40.867,0:10:46.571
birthday present with a sweater in order[br]to fool me. So we could make that a little

0:10:46.571,0:10:52.000
more explicit by making the suppressed[br]premise something like this. If this box

0:10:52.000,0:10:57.704
contains a sweater, then it only contains[br]a sweater and it doesn't include anything

0:10:57.704,0:11:03.385
else that would make a rattling sound when[br]shaken. And now we can stick that as an

0:11:03.385,0:11:08.369
extra suppressed premise into the[br]argument. Now the argument looks like

0:11:08.369,0:11:14.846
this. This box rattles when I shake it. A[br]box doesn't rattle when shaken, if it

0:11:14.846,0:11:20.976
contains only a sweater and not anything[br]else that makes a rattling noise when

0:11:20.976,0:11:27.627
shaken. If this box contains a sweater,[br]then it contains only a sweater and

0:11:27.627,0:11:34.382
doesn't contain anything that rattles when[br]shaken. So this box does not contain a

0:11:34.382,0:11:39.775
sweater. Now we have an argument that's[br]valid. And the suppressed premises are

0:11:39.775,0:11:44.980
true, at least given our life's not a[br]trickster, which she's not, I assure you.

0:11:44.980,0:11:51.005
And it looks like we have a sound rec[br]onstruction, just what we were looking

0:11:51.005,0:11:56.351
for. Admittedly, this argument is a lot[br]longer and more convoluted than the

0:11:56.351,0:12:01.685
original, and that shows why people[br]suppress premises instead of talking the

0:12:01.685,0:12:06.774
way this argument goes. And of course,[br]many people would be perfectly well

0:12:06.774,0:12:12.750
convinced by the original argument because[br]they share the assumptions that are in the

0:12:12.750,0:12:18.240
suppressed premises. So why do we go[br]through all the trouble to go through this

0:12:18.240,0:12:22.896
process and add the suppressed premises?[br]Remember, the reason is that we want to

0:12:23.313,0:12:27.621
understand the pathway between the[br]premises and conclusion. We want to

0:12:28.038,0:12:33.228
understand how the reasoning works step by[br]step by step. And we want to do that

0:12:33.228,0:12:37.632
because sometimes people are going to[br]include suppressed premises that aren't

0:12:37.632,0:12:42.261
true, and we want to bring them out and[br]make those assumptions explicit so that we

0:12:42.261,0:12:46.881
can assess them for truth and falsehood.[br]And when you're talking to somebody you

0:12:46.881,0:12:51.605
trust, you might not have to do that and[br]it's okay to suppress premises. But when

0:12:51.605,0:12:56.151
you really want to know whether the[br]argument's any good, that's when you want

0:12:56.151,0:13:00.579
to fill it out with the suppressed[br]premises. The point of going into detail

0:13:00.579,0:13:04.992
on this example is to illustrate this[br]stage of reconstruction. You want to

0:13:04.992,0:13:09.757
assess the argument for validity, add[br]suppressed premises that make it valid.

0:13:09.757,0:13:14.710
Check them for truth. If they're not true,[br]you qualify them, and then you go back and

0:13:14.710,0:13:19.600
see whether that qualification made the[br]argument not valid anymore. And you go

0:13:19.600,0:13:24.508
back and forth and back and forth until[br]you've got a sound reconstruction. The

0:13:24.508,0:13:29.807
same steps are going to apply to all kinds[br]of suppressed premises. And sure enough,

0:13:29.807,0:13:34.436
there are all kinds of suppressed[br]premises. So let's go through a few

0:13:34.436,0:13:39.802
examples a lot more quickly in order to[br]show the variety of suppressed premises

0:13:39.802,0:13:46.782
that are assumed in arguments. Here's one[br]example. Abraham Lincoln turned 40. On

0:13:46.782,0:13:57.957
February twelfth, 1849. Therefore, Charles[br]Darwin also turned 40 on February twelfth,

0:13:57.957,0:14:04.109
1849. Now, is that argument valid? No[br]chance. Of course it's possible for the

0:14:04.109,0:14:09.576
premise to be true and the conclus ion[br]false. So we have to add a suppressed

0:14:09.576,0:14:15.309
premise. The suppressed premise is, that[br]Abraham Lincoln and Charles Darwin were

0:14:15.309,0:14:20.637
born on the same day. And they were, it[br]happened to be February twelfth, 1809. So

0:14:20.637,0:14:27.132
now, we've filled out the argument.[br]Abraham Lincoln turned 40 on February

0:14:27.132,0:14:33.451
twelfth, 1849. Abraham Lincoln and Charles[br]Darwin were born on the same day,

0:14:33.451,0:14:39.545
therefore Charles Darwin also turned 40 on[br]February twelfth, 1849. Now is the

0:14:39.545,0:14:46.682
argument valid? No. It's still not valid.[br]Cuz Darwin might have died before 1849. So

0:14:46.682,0:14:53.017
we have to add another suppressed premise.[br]Mainly, that both Abraham Lincoln and

0:14:53.017,0:14:59.665
Charles Darwin lived beyond 40. So now we[br]have a fuller argument. Abraham Lincoln

0:14:59.665,0:15:07.033
turned 40 on February twelfth, 1849.[br]Abraham Lincoln and Charles Darwin were

0:15:07.033,0:15:14.406
born on the same day. Both of them lived[br]beyond the age of 40. Therefore, Charles

0:15:14.406,0:15:20.997
Darwin also turned 40 on February twelve,[br]1849. Now the argument looks pretty good.

0:15:20.997,0:15:26.576
We had to have two suppressed premises but[br]we finally have a valid argument. And what

0:15:26.576,0:15:31.301
this shows is that sometimes the[br]suppressed premises are purely factual

0:15:31.301,0:15:36.683
matters. In this case that they were born[br]on the same day and that they both lived

0:15:36.683,0:15:42.077
beyond 40. So sometimes we have factual[br]suppressed premises. Here's another quick

0:15:42.077,0:15:46.952
example. You ought to obey her because[br]she's your mother. Here, the premise is

0:15:46.952,0:15:52.445
that she's your mother and the conclusion[br]is that you ought to obey her. Well, is

0:15:52.445,0:15:57.870
that argument valid? No way cause it's[br]possible that she's your mother but it's

0:15:57.870,0:16:03.020
false that you ought to obey her. When[br]could that happen? Maybe, she was like

0:16:03.020,0:16:08.933
abusive or stupid or whatever. Then maybe[br]you ought not to obey her even though she

0:16:08.933,0:16:14.241
is your mother. So we have to add a[br]premise, namely, you ought to obey your

0:16:14.241,0:16:19.244
mother. Now we can say she's your mother,[br]you ought to obey your mother therefore

0:16:19.244,0:16:24.540
you ought to obey her, but of course that[br]a supressed premise you ought to obey your

0:16:24.540,0:16:29.219
mother is questionable because maybe she[br]was abusive or stupid. So let's add

0:16:29.219,0:16:34.268
another supressed premise that your mother[br]was not abusive or stupid, of course we a

0:16:34.268,0:16:39.071
lso have to qualify that moral premise[br]that you ought to obey your mother if

0:16:39.071,0:16:43.812
she's not abusive or stupid. And now the[br]argument looks like this - she's your

0:16:43.812,0:16:48.900
mother, you ought to obey your mother if[br]she's not abusive or stupid. Your mother

0:16:48.900,0:16:54.880
was not abusive or stupid. Therefore, you[br]ought to obey her. An notice that here, we

0:16:54.880,0:17:00.409
added a moral premise about the fact that[br]you ought to obey your mother under

0:17:00.409,0:17:05.867
certain conditions. Namely, she's not[br]abusive or stupid. And the second premise

0:17:05.867,0:17:11.042
is she was not abusive or stupid. So, we[br]have a moral premise and a factual

0:17:11.042,0:17:16.216
premise, both being suppressed in the[br]argument that you ought to obey her

0:17:16.216,0:17:22.633
because she's your mother. Here's another[br]. It's the Sabbath, so you ought to go to

0:17:22.633,0:17:28.521
synagogue. Well, that's clearly not valid.[br]One suppressed premise is that you're

0:17:28.521,0:17:34.291
Jewish. The other suppressed premise is[br]you haven't been to synagogue already

0:17:34.291,0:17:39.906
today, on this Sabbath. And the third[br]suppressed premise is a religious norm,

0:17:39.906,0:17:45.735
mainly Jews ought to go to the synagogue[br]on the Sabbath. And you need that whole

0:17:45.735,0:17:50.912
bunch of suppressed premises in order to[br]get from the premise, that it's the

0:17:50.912,0:17:56.339
Sabbath, to the conclusion, that you ought[br]to go to synagogue. And of course all of

0:17:56.339,0:18:01.504
those premises might be questionable. Some[br]people would question them. Some people

0:18:01.504,0:18:06.910
would deny them, but the point here is to[br]figure out what's being assumed by someone

0:18:06.910,0:18:11.814
who gave the original argument. And[br]anybody who says it's the Sabbath, so you

0:18:11.814,0:18:16.203
ought to go to synagogue, seems to be[br]assuming you're Jewish, you haven't been

0:18:16.203,0:18:21.152
already, and Jews ought to go to the[br]synagogue on the Sabbath. So what these

0:18:21.152,0:18:26.938
suppressed premises do is they bring out[br]the assumptions that somebody who gave

0:18:26.938,0:18:32.869
that argument must have had in mind. The[br]last case is a little bit trickier. It has

0:18:32.869,0:18:38.800
to do with linguistic suppressed premises.[br]Jen and Bob are first cousins, therefore

0:18:38.800,0:18:47.470
they share a grandparent. Now, in order to[br]understand that argument, you have to know

0:18:47.470,0:18:52.162
that first cousins always share a[br]grandparent. That just follows from the

0:18:52.162,0:18:58.847
definition of what a first cousin is. But[br]i t's not quite so obvious, is that

0:18:58.847,0:19:04.002
biological sisters are female. And so,[br]there's even more need to bring out that

0:19:04.002,0:19:09.356
linguistics suppressed premise in this[br]case. But it's still not necessary to make

0:19:09.356,0:19:14.843
the argument valid. It's just not possible[br]that Janet and Bob are first cousins, and

0:19:14.843,0:19:19.602
they don't share a grandparent. Because[br]the suppressed premise is purely

0:19:19.602,0:19:24.663
linguistic, so it's necessarily true, so[br]you can't possibly be first cousins

0:19:24.663,0:19:29.700
without sharing a grandparent. Still, the[br]point of bringing out linguistic

0:19:29.700,0:19:34.944
suppressed premises is to show every[br]little step along the way. The argument

0:19:34.944,0:19:39.952
might be valid without those suppressed[br]linguistic premises, but we won't

0:19:39.952,0:19:45.153
understand why it's valid and why the[br]reasoning goes through unless we add the

0:19:45.153,0:19:51.412
linguistics suppressed premise. So it's[br]worth doing that. Shh. Here's a trick.

0:19:51.412,0:20:00.400
Don't tell anybody. Okay? It's just[br]between me and you. You can always make

0:20:00.400,0:20:06.916
any argument valid just by adding a[br]suppressed premise that says if the

0:20:06.916,0:20:14.069
premises are true, then the conclusion is[br]true. But don't tell anybody, because if

0:20:14.069,0:20:19.991
people start doing that, and they start[br]making the argument valid that way, with

0:20:19.991,0:20:26.270
that suppressed premise, we're never going[br]to understand the pathway of reasoning. It

0:20:26.270,0:20:31.095
makes the argument valid, but it doesn't[br]serve the real purpose of adding

0:20:31.578,0:20:37.231
suppressed premises which is to understand[br]the pathway of reasoning. So you can do

0:20:37.231,0:20:42.677
that. It's a trick. It makes that argument[br]valid but it doesn't achieve our goal

0:20:42.677,0:20:48.330
because our goal is not just to make the[br]argument valid, it's to make the argument

0:20:48.330,0:20:54.604
valid so that we can understand the[br]pathway of reasoning. So it's important to

0:20:54.604,0:21:02.339
know that trick, but don't use it unless[br]you have to. The examples so far have been

0:21:02.339,0:21:07.850
pretty trivial, I admit it. But the same[br]points apply in very important context

0:21:07.850,0:21:13.573
such as politic debates, politician can[br]suppress premises in perfectly legitimate

0:21:13.573,0:21:19.508
ways. They're just trying to save time and[br]make their arguments more efficient, maybe

0:21:19.508,0:21:25.615
even sometimes clearer because you don't[br]have to add all those little details. But

0:21:25.615,0:21:31.684
sometimes politicia ns abuse suppressed[br]premises. They take things for granted

0:21:31.684,0:21:37.910
that they shouldn't be taking for granted.[br]Here's an example. A politician might

0:21:37.910,0:21:43.980
argue, my opponent is soft on crime[br]because he's opposed to the death penalty.

0:21:44.300,0:21:50.016
Well, that assumes, as a suppressed[br]premise, that anyone who's opposed to the

0:21:50.016,0:21:56.143
death penalty must be soft on crime. And[br]if the politician were to come out and say

0:21:56.143,0:22:01.460
that, it would seem pretty questionable,[br]and that's probably why he suppresses it.

0:22:01.720,0:22:07.446
And then another politician might say, my[br]opponent is in favor of the death penalty,

0:22:07.446,0:22:13.034
so he must not have read all the recent[br]studies that show that the death penalty

0:22:13.034,0:22:18.977
doesn't deter. Well that argument assumes[br]the suppressed premise that if you've read

0:22:18.977,0:22:23.556
those studies you'ld be convinced by them,[br]and that the only point of the death

0:22:23.556,0:22:29.642
penalty is deterrence. But the point is[br]that politicians talking about extremely

0:22:29.642,0:22:34.047
important issues can take things for[br]granted, that if they were brought into

0:22:34.047,0:22:38.858
the light of day will be questionable, and[br]that's why they hide them. So when you're

0:22:38.858,0:22:43.500
listening to people give arguments on[br]important issues in your life, then you

0:22:43.500,0:22:49.802
ought to be looking for these suppressed[br]premises and asking yourself whether or

0:22:49.802,0:22:55.949
not you really ought to be agreeing with[br]them about that assumption. Finally, we

0:22:55.949,0:23:01.628
finished reconstruction. Yipee, right? Oh,[br]no, not quite, because there's one more

0:23:01.628,0:23:06.951
stage, and that stage is drawing a[br]conclusion. Of course, if we've come up

0:23:06.951,0:23:12.349
with a sound reconstruction, then we know[br]that the argument is sound, and we know

0:23:12.349,0:23:18.817
that the conclusion is true, because every[br]sound argument has a true conclusion. But

0:23:18.817,0:23:23.519
if we don't come up with a sound[br]reconstruction, then what do we say? Well,

0:23:23.519,0:23:28.415
you've got to ask, whose fault is it? It[br]might be the fault of the argument. Maybe

0:23:28.415,0:23:33.117
we couldn't come up with a sound[br]reconstruction because there just is no

0:23:33.117,0:23:37.240
sound reconstruction. But maybe we[br]couldn't come up with a sound

0:23:37.240,0:23:42.200
reconstruction because we just weren't[br]imaginative enough, or try hard enough.

0:23:42.200,0:23:47.592
Still, if we try really long an hard, and[br]charitably interpret the a rgument as best

0:23:47.592,0:23:52.919
we can to make it, look as good as we can,[br]and we still can't make it sound. Then,

0:23:52.919,0:23:58.312
we've at least got reason to believe that[br]the argument's not sound. Of course, that

0:23:58.312,0:24:03.573
doesn't mean that the conclusion's not[br]true, because unsound arguments can still

0:24:03.573,0:24:09.107
have true conclusions. But at least we[br]know that this argument doesn't prove that

0:24:09.107,0:24:14.094
the conclusion is true. And so, this[br]method of reconstruction can lead us

0:24:14.094,0:24:19.290
either to the belief that the argument is[br]sound, because we found the sound

0:24:19.290,0:24:24.831
reconstruction, or to the conclusion is[br]not sound, because we tried long and hard

0:24:24.831,0:24:30.234
to find a sound reconstruction that[br]didn't, but that's still not going to show

0:24:30.234,0:24:36.546
us that the conclusion of the argument is[br]false. The point of reconstruction then is

0:24:36.546,0:24:42.347
to reach a conclusion on this issue of is[br]the argument sound or not. And if we try

0:24:42.347,0:24:48.007
our best and do it as well as we can and[br]charitably, then we can be justified in

0:24:48.007,0:24:51.120
believing that the argument is sound or[br]not.