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Welcome back. We've covered stages one
through three of argument reconstruction
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namely, close analysis, get down to
basics, and sharpen edges. In this
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lecture, we'll cover stage four, which is
organized parts. Cuz it's not enough to
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isolate the parts and figure out what they
are. We need to show how the fit together
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in a structure so that they work together
to support the conclusion of the argument.
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To see how this works, let's start with an
example. Consider this example. That
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fertilizer won't help the roses bloom cuz
there is already a lot of nitrogen in the
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soil. So, the fertilizer will make the
nitrogen levels too high. Of course, so is
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a conclusion marker so one conclusion is
that, the fertilizer will make the
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nitrogen levels too high. And then, you
might think that one might have put the
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argument into standard form goes like
this. Premise one is that fertilizer won't
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make the roses bloom. Premise two is the
nitrogen levels in the soil are already
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high. And then, the conclusion is that the
fertilizer will make the nitrogen levels
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too high. But that doesn't really make any
sense, if you think about it. How could
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the fact that the roses won't bloom be a
reason to believe that the nitrogen levels
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are too high? This couldn't be a reason
for that. So, we might just have the wrong
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structure. However, there is another
argument marker. This time it's a premise
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marker, because. And that indicates that
the claim that there's already a lot of
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nitrogen in the soil is a premise. But
what is the conclusion for that premise?
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That's supposed to show that the
fertilizer won't make the roses bloom. So,
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we've missed that part of the structure if
we put it in standard form, the way we
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first thought. The trick here is that
there are really two conclusions. One
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conclusion is that the fertilizer won't
help the roses bloom, and another
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conclusion is that the fertilizer will
make the nitrogen levels too high. But
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each argument's just supposed to have one
conclusion. So, how are we going to put
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this into a structure? The solution is
that there are two arguments. One is that
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the nitrogen levels in the soil are
already high. Therefore, adding the
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fertilizer will make them too high. And
the second argument is that, adding the
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fertilizer will make the nitrogen levels
too high, therefore the fertilizer will
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not make the roses bloom. Now notice that
one argument really builds on the other
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because the conclusion of the first
argument is really a premise in the second
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argument. So, we can represent them as two
separate arguments. But we can also put
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them together in a chain. So that the
argument says, the nitrogen levels in the
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soil are already high. Therefore, adding
fertilizer will make them too high. And
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therefore, adding fertilizer will not help
the roses bloom. Now, if we take that
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whole structure and we try to represent it
in a diagram, and we represent each
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premise with a number, which is the number
that was given in the standard form, then
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we can simply have premise one with an
arrow to premise two indicating that
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premise one is a reason for premise two.
And then, another arrow going from premise
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two to premise three to indicate that two
is a reason for three. In a way, we've got
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two premises and two conclusions because
that one kind in the middle, number two,
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operates as a conclusion in the first
argument and a premise in the second
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argument. But overall, I hope the diagram,
its clear. Well, I want to call this
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linear structure. When you have one
premise giving reason for a conclusion
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which is then premise for another
conclusion, then they form a line in the
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diagram them in the way that I am
proposing. Arguments can have other
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structures, too. In particular, sometimes
there's more than one premise associated
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with a single conclusion. And this can
happen in two ways. The first, we're going
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to call the branching structure, and the
second we're going to call the joint
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structure. Here is an example of the
branching structure. I'm not going to go
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to the movie with you because I don't like
horror flicks. And besides, I'm too busy.
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The word beca use is a premise marker. So
that indicates that the conclusion is
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that, I'm not going to go to the movie
with you. And there are two premises. One
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is, I don't like horror flicks, and the
other is, I'm too busy. Now, you might
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think that, that could just be put in the
old linear structure that we already saw.
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But then, the argument's going to look
like this. I don't like horror flicks.
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Therefore, I'm too busy. Therefore, I'm
not going to go to the movie. But, wait a
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minute. The fact that I don't like horror
flicks doesn't mean I'm too busy. That
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doesn't make any sense. Oh, maybe it's the
other way around. I'm too busy. Therefore,
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I don't like horror flicks. Therefore, I'm
not going to go to that movie with you.
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That doesn't make any sense either. The
fact that I'm too busy isn't why I don't
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like horror flicks. The problem is, there
are two premises here but neither one is a
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reason for the other, as we saw in the
linear structure. Instead, in this
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branching structure, each premise is
operating independently. There's one
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argument. I don't like horror flicks,
therefore I'm not going to go to that
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movie with you. There's another argument.
I'm too busy, therefore I'm not going to
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that movie with you. And each premise by
itself is a sufficient reason not to go to
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the movie with you. I mean, just think
about it. If I wasn't too busy, but I
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didn't like horror flicks, I wouldn't go
to the movie. But if I liked horror
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flicks, but I was too busy, I still would
go to the movie. So, each premise by
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itself is enough, and they operate
independently. That's what makes this a
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branching structure instead of a linear
structure. Let's diagram it and you'll see
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why we call it a branching structure. One
way to diagram it would be to simply draw
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an arrow between premise one and the
conclusion two. And then, there's a
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separate argument, so you draw another
arrow from one star, another premise, to
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conclusion two. And that's okay. But,
notice that it doesn't show you that both
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premises are reasons for the same
conclusion. So, to capture t hat aspect of
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the structure, that both Premise one and
Premise one Star support the same
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conclusion, namely two. It's better to
diagram it so that there's an arrow that
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runs independently from both premises to a
single instance of conclusion two, as you
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see on the diagram on the screen. And that
should show you why we're calling it a
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branching structure cuz it kind of
branches, it looks like the branches of a
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tree. Okay. Well, it doesn't really look
like the branches of a tree, but you get
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the idea. We're going to call it a
branching structure. Next, we have to
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separate this branching structure from
what we're going to call the joint
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structure. The difference is that in the
branching structure, the premises provide
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independent support for the conclusion.
Whereas, in this joint structure, they
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work together and they're not going to
have force independent of each-other. It's
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like the joint in your leg, which joins
together the calf with the thigh. And, if
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you didn't have both, it wouldn't work
very well. So, we're going to call it a
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joint structure. Here's an example. For my
birthday, my wife always gives me either a
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sweater or a board game. This box does not
contain a sweater. So, this time she must
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have given me a board game. Now, notice
that the argent marker, so, indicates that
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the conclusion is, this time she must've
given me a board game. And it's got two
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premises. And you might think that they
got a linear structure, and the argument
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goes something like this. My wife always
gives me either a sweater or board games.
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Therefore, this box does not contain a
sweater. Therefore, this time she gave me
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board game. That doesn't make any sense,
right? I mean, the fact that she always
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gives me either a sweater or board game is
no reason to believe this box doesn't
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contain a sweater. Well, okay. Let's try
it again. Maybe it's a branching
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structure. That would mean that the
argument looks like this. My wife always
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gives me either a sweater or a board game.
Therefore, this time she gave me a board
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game. And, as a separat e argument, this
box does not contain a sweater, therefore
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this time she must have given me a board
game. Neither of those arguments makes any
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sense so it can't be a branching
structure. Instead, what we have here is
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the two premises working together. She
always gives me either a sweater or a
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board game. And, the second premise, this
box does not contain a sweater. Those two
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premises have to work together. It's only
jointly working together that they can
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support the conclusion that, this time she
must have given me a board game. How can
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we diagram this joint structure? We can
put a plus sign between premise one and
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premise two, then draw a line under them
to show that they work together jointly.
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And take a line from that line and draw an
arrow down to the conclusion, just like in
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the diagram. And this is what we're going
to call the joint structure. So, we've
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seen the linear structure, the branching
structure, and the joint structure. And,
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we can combine more than one of these
structures into a single argument. To see
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how to do this, let's just do a slight
variation on the previous example. My wife
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always gives me either a sweater or a
board game. This is box is not contain a
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sweater because it rattles when I shake
it. So, this time she must have given me a
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board game. This argument combines a
linear structure with a joint structure.
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There are two argument markers. One is a
conclusion marker, so, and that indicates
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that the eventual conclusion is that she
must given me a board game this time. But
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there's also that new word, because, which
indicates that the fact that it rattles
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when I shake means that it's not a
sweater. So, the first stage of the
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argument in standard form looks like this.
Premise one, this box rattles when I shake
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it. Therefore, conclusion, this box does
not contain a sweater. Stage two says,
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this box does not contain a sweater, my
wife always gives me either a sweater or a
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board game. So, the conclusion, this time,
she must have given me a board game. And,
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of course, the conclusion of that fir st
little argument is identical with the
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premise of the second argument, so we can
put them together into a chain. We can
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say," this box rattles when I shake it, so
it must not contain a sweater." My wife
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always gives me a sweater or a board game,
so this time she must have given me a
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board game. That's how we get a linear
structure combined with a joint structure.
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And we can use our diagram methods to
diagram this argument the same way we did
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before. We simply start with premise one,
the box rattles when I shake it. Draw an
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arrow down to its conclusion. Namely, the
box does not contain a sweater. That's
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two. An then, we show that those are joint
by adding a plus, premise three. Namely,
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my wife always gives me either a sweater
or a board game. Draw a line under them
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and an arrow from those two together down
to the eventual conclusion, namely, four
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that this time she must have given me a
board game. The fact that the top arrow
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goes from premise one to two, but does not
go from premise one to three indicates
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that, that premises is a reason for two
but is not a reason for three. So when you
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use this method to diagram arguments, you
have to be careful where you draw the
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arrows. And draw them only where there
really is a rational connection. That is,
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where one claim is being presenting as a
reason for that particular claim that the
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arrow is pointing towards. Now, almost all
arguments can be diagrammed using these
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three simple structures. That is, the
linear structure, the branching structure,
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the joint structure, and some combination
of those three. You can add more premises
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because you can always add one plus two
plus three plus four if they're four
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premises operating together in a joint
structure. And, you can add extra arrows
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if you have a branch with more than two
branches. So, you can cover a lot of
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arguments using these kinds of diagrams.
The method can be described in general,
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like this. You start by identifying the
premises and the conclusions, and you
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number them. So that you can just have
numbers instead of having to write out the
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whole sentence on the diagram. Then, when
they work together, you put a plus sign
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between them and draw a line under it to
indicate that they're working together.
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They're functioning as a group. Then, you
draw an arrow from the claims that are
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reasons to the claims that they are
reasons for. And then, you move them
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around on the diagram so that they'll form
a line when it's a linear structure and
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branches when it's a branching structure.
But, it will be easy to rearrange them so
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as to show how all of the different
premises and conclusions work together in
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a single argumentative structure. That's
going to be enough to accomplish this
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stage of reconstruction. Namely, to
organize the parts and show how they work
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together in the overall argument.