How to Understand Arguments Think Again: How to Reason and Argue Reasoning is important. This series of four short courses will teach you how to do it well. You will learn simple but vital rules to follow in thinking about any topic at all and common and tempting mistakes to avoid in reasoning. We will discuss how to identify, analyze, and evaluate arguments by other people (including politicians, used car salesmen, and teachers) and how to construct arguments of your own in order to help you decide what to believe or what to do. These skills will be useful in dealing with whatever matters most to you. Courses at a Glance: All four courses in this series are offered through sessions which run every four weeks. We suggest sticking to the weekly schedule to the best of your ability. If for whatever reason you fall behind, feel free to re-enroll in the next session.We also suggest that you start each course close to the beginning of a month in order to increase the number of peers in the discussion forums who are working on the same material as you are. While each course can be taken independently, we suggest you take the four courses in order. Course 1 - Think Again I: How to Understand Arguments Course 2 - Think Again II: How to Reason Deductively Course 3 - Think Again III: How to Reason Inductively Course 4 - Think Again IV: How to Avoid Fallacies About This Course in the Series: When is someone giving an argument instead of just yelling? Which parts of what they say contribute to the argument? Why are they arguing instead of fighting? What are arguments made of? What forms do they take? Think Again: How to Understand Arguments will answer these questions a more. In this course, you will learn what an argument is. The definition of argument will enable students to identify when speakers are giving arguments and when they are not. Next, we will learn how to break an argument into its essential parts, how to put them in order to reveal their connections, and how to fill in gaps in an argument. By the end of this course, students will be better able to understand and appreciate arguments that they and other people present. Suggested Readings: Students who want more detailed explanations or additional exercises or who want to explore these topics in more depth should consult Understanding Arguments: An Introduction to Informal Logic, Ninth Edition, Concise, Chapters 1-5, by Walter Sinnott-Armstrong and Robert Fogelin. Course Format: Each week will be divided into multiple video segments that can be viewed separately or in groups. There will be short ungraded quizzes after each segment (to check comprehension) and a longer graded quiz at the end of the course.
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From the course by Duke University
Think Again I: How to Understand Arguments
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From the lesson
How to Reconstruct an Argument
<p><b>CONTENT</b>: This week’s material will teach you how to organize the parts of an argument in order to show how they fit into a structure of reasoning. The goal is to make the argument look as good as possible so that you can learn from it. We work through the main steps of reconstruction, including putting the premises and conclusion into a standard form, clarifying the premises and breaking them into parts, arranging the argument into stages or sub-arguments, adding suppressed premises where needed to make the argument valid, and assessing the argument for soundness. The lectures begin by defining the crucial notions of validity, soundness, and standard form. You will also learn to diagram alternative argument structures, including linear, branching, and joint structures. <p><b>LEARNING OUTCOMES</b>: By the end of this week’s material, you will be able to:<ul> <li>label assuring, guarding, discounting, and evaluative terms</li> <li>determine whether an argument is valid or sound</li> <li>complete arguments by adding suppressed premises</li> <li>reconstruct arguments by and series of arguments</li> <li>classify argument structures</li></ul><p><b>OPTIONAL READING</b>: If you want more examples or more detailed discussions of these topics, we recommend <em>Understanding Arguments, Ninth Edition</em>, Chapter 5.
Meet the Instructors
Dr. Walter Sinnott-ArmstrongProfessor
Philosophy
Dr. Ram NetaProfessor
Philosophy
Welcome back.
We've covered stages one through three of argument reconstruction.
Namely, close analysis, get down to basics, and sharpen
edges. In this lecture, we'll cover stage four.
Which is organized parts.
because it's not enough to isolate the parts and figure out what they are.
You need to show how they fit together in a structure, so that
they work together to support the conclusion of the argument.
To see how this works, let's start with an example.
Consider this example.
That fertilizer won't help the roses bloom, because
there's already a lot of nitrogen in the soil.
So the fertilizer will make the nitrogen levels too high.
Of course, so is a conclusion marker.
So one conclusion is that,
the fertilizer will make the nitrogen levels too high.
And then you might think that one might have
put the argument into standard form goes like this.
Premise one is, that fertilizer won't make the roses bloom.
Premise two is, the nitrogen levels in the soil are already high.
And then the conclusion is, that the
fertilizer will make the nitrogen levels too high.
But that
doesn't really make any sense if you think about it.
How could the fact that the roses won't bloom, be
a reason to believe that the nitrogen levels are too high?
This couldn't be a reason for that, so we must have the wrong structure.
However, there's another argument marker.
This time it's a premise marker. Because.
And that indicates that the claim that there's already
a lot of nitrogen in the soil is
a premise, but what's the conclusion for that premise.
That's supposed to show that the fertilizer won't make the roses bloom.
So we've missed that part of the structure.
If we put it in standard form the way we first thought.
The trick here is that there is really two conclusions.
One conclusion is that the fertilizer won't help the roses bloom.
And another conclusion is that the fertilizer will make the nitrogen levels
too high, but each argument is supposed to have just one conclusion.
So how are we going to put this into a structure?
The solution is that there are two arguments.
One is that the nitrogen levels in the soil are already high.
Therefore, adding the fertilizer will make them too high.
And the second argument is that. Adding the fertilizer will make
the nitrogen levels too high. Therefore, the fertilizer will not make
the roses bloom.
Now notice that one argument really builds on the other, because the
conclusion of the first argument is really a premise in the second argument.
So we can represent them as two separate arguments,
but we can also put them together in a chain.
So that the argument says, the nitrogen levels in
the soil are already high, therefore adding fertilizer will make
them too high.
And therefore, adding fertilizer will not help the roses bloom.
Now, if we take that whole structure, and we try to represent
it in a diagram, and we represent each premise with a number.
Which is the number that was given it in
the standard form, then we can simply have premise one.
With an arrow to premise two indicating that
premise one is a reason for premise two.
And then another arrow going from premise two to premise
three to indicate that two is a reason for three.
In a way, we've got two premises and two conclusions because, that one claim in the
middle, number two, operates as a conclusion in
the first argument, and premise in the second argument.
But overall, I hope the diagram makes it
clear why I want to call this a linear structure.
When you have one premise giving a reason for
a conclusion, which is then a premise for another conclusion.
Then they form a line when you diagram them in the way that I'm proposing.
Arguments can have other structures too.
In particular, sometimes there's more than
one premise associated with a single conclusion.
And this can happen in two ways.
The first we're going to call the branching structure.
And the second we're going to call the joint structure.
Here's an example of the branching structure.
I'm not going to go to the movie with you because I don't like horror flicks.
And besides, I'm too busy.
The word because is a premise marker. So that indicates that the conclusion
is that I'm not going to go to the movie with you.
And there are two premises.
One is I don't like horror flicks, and the other is I'm too busy.
Now you might think that, that could just be
put in the old linear structure that we already saw.
But then the argument's going to look like this.
I don't like horror flicks therefore, I'm
too busy, therefore, I'm not going to go to
the movie. But wait a minute.
The fact that I don't like horror flicks doesn't mean I'm too busy.
That doesn't make any sense. Oh, maybe it's the other way around.
I'm too busy, therefore, I don't like horror flicks,
therefore, I'm not going to go to that movie with you.
That didn't make any sense either.
The fact that I'm too busy isn't why I don't like horror flicks.
The problem is there are two premises here, but neither one is a reason
for the other, as we saw on the linear structure.
Instead, in this branching structure, each premise is operating independently.
There's one argument.
I don't like horror flicks, therefore I'm not going to go to that movie with you.
There's another argument.
I'm too busy, therefore I'm not going to go to that movie with you.
And each premise by itself is a sufficient reason not to go to the movie
with you. I mean just think about it.
If I wasn't too busy but I didn't like horror flicks, I wouldn't go to the movie.
But if I liked horror flicks but I was
too busy, then I still wouldn't go to the movie.
So each premise itself, is enough and they operate independently.
That's what makes this a branching structure, instead of a linear structure.
Lets diagram it and you will see why we call it a branching structure.
One way to diagram it would be simply draw
an arrow between premise one and conclusion two, and
then there's a separate argument, so you draw another
arrow from one star, another premise to conclusion two.
And that's okay, but notice that it doesn't show
you that both premises are reasons for the same conclusion.
So to capture that aspect
of the structure, that both premise one and premise one star support
the same conclusion, namely two, it's better to diagram it so that.
There's an arrow that runs independently from both premises to a single
instance of conclusion two, as you see in the diagram on the screen.
And that should show you why we're calling it
a branching structure, because it kind of branches, it looks like
the branches of a tree.
Okay, it doesn't really look like the branches of a tree, but you get the idea.
We're going to call it a branching structure.
Next, we have to separate this branching structure
from what we're going to call the joint structure.
The difference is that in the branching structure
the premises provide independent support for the conclusion.
Whereas in this joint structure, they work together.
And they're not going to have force independent of
each other. It's like the joint in your leg.
Which joins together the calf with the thigh.
And if you didn't have both, it wouldn't work very well.
So we're going to call it a joint structure.
Here's an example.
For my birthday, my wife always gives me either a sweater or a board game.
This box does not contain a sweater. So, this time she must have given me a
board game. Now notice that the argument marker, so,
indicates that the conclusion is this time she must have given me a board game.
And it's got two premises.
And you might think that they got a
linear structure, and the argument goes something like this.
My wife always give me a sweater or a board game.
Therefore, this box does not contain a sweater.
Therefore,
this time she gave me a board game. That didn't make any sense, right?
I mean the fact that she always give me a sweater or a board
game gives me no reason to believe that this box doesn't contain a sweater.
Well, okay, let's try it again.
Maybe it's a branching structure.
That would mean that the argument looks like this.
My wife always gives me either a sweater or a board game.
Therefore, this time she gave me a board game.
And as a separate argument, this box does not contain a sweater.
Therefore, this time she must have given me a board game.
Neither of those arguments makes any sense.
So it can't be a branching structure.
Instead what we have here is the two premises working together.
She always gives me either a sweater or a board game.
And, the second premise, this box does not contain a sweater.
Those two premises have to work together.
It's only jointly working together that they can support their conclusion this
time she must have given me a board game. How can we diagram this joint structure.
We can put, a plus sign between premiss one and premiss two.
Then draw a line under them to show that they work together, jointly.
And take a line from that line, and draw an
arrow down to the conclusion, just like in the diagram.
And this is what we're going to call the joint structure.
So, we've seen the linear structure,
the branching structure, and the joint structure.
And we can
combine more than one of these structures into a single argument.
To see how to do this, let's just do a slide variation on the previous example.
My wife always gives me either a sweater or a board game.
This box does not contain a sweater.
Because it rattles when I shake it.
So, this time she must have given me a board game.
This argument
combined a linear structure with a joint structure.
There are two argument markers.
One's a conclusion marker, so and that indicates that the eventual conclusion
is that she must of given me a board game this time.
But there's also that new word because, which indicates that the fact
that it rattles when I shake it, means that it's not a sweater.
So the first stage if the argument in standard form
looks like this.
Premise one, this box rattles when I shake it.
Therefore, conclusion, this box does not contain a sweater.
Stage two says this box does not contain a sweater.
My wife always gives me either a sweater or a board game.
So the conclusion, this time she must have given me a board game.
And of course, the conclusion of that first little argument.
Is identical with the premise of the second argument.
So we can put them together into a chain.
We can say, this box rattles when I shake it, so it must not contain a sweater.
My wife always gives me a sweater or a board game
so, this time she must have given me a board game.
That's how we get a linear structure,
combined with a joint structure.
And we can use our diagram methods to
diagram this argument the same way we did before.
We simply start with premise one, the box rattles when I shake it, drawn
an arrow down to its conclusion, namely, the box does not contain a sweater.
That's two, and then we show that those are joint by adding a
plus premise three, mainly, my wife always gives me either a sweater or a board game.
Draw a line under them and an arrow from
those two together, down to the eventual conclusion namely, four.
That this time she must have given me a board game.
The fact that the top arrow goes from premise one to two, but does not
go from premise one to three, indicates that, that premise is
a reason for two, but is not a reason for three.
So when you use this method to diagram arguments,
you have to be careful where you draw the arrows.
And draw them only where there really is a rational connection.
That is where one claim is being presented as a
reason for that particular claim that the arrow's pointing towards.
Now almost
all arguments can be diagrammed using these three simple structures, that is the
linear structure, the branching structure, the joint
structure, and some combination of those three.
You can add more premises, because you can
always add one plus two plus three plus four.
If there are four premises operating together in a joint structure.
And you can add extra
arrows if you have a branch with more than two branches, so
you can cover a lot of arguments using these kinds of diagrams.
The method can be described in general like this.
You start by identifying the premises and the conclusions, and you number them.
So that you can just have numbers instead of
having to write out the whole sentence on the diagram.
Then when they work together, you put a plus sign between them and
draw a line under it to indicate that
they're working together, they're functioning as a group.
Then, you draw an arrow from the claims that
are reasons to the claims that they are reasons for.
And then you move them around on the diagram so that they form
a line when it's a linear structure, and branches when it's a branching structure.
That'll be easy to rearrange them. So as to show how all of the
different premises, and conclusions work
together in a single argumentative structure.
That's going to be enough to accomplish this stage of reconstruction, namely to
organize the parts and show how they work together in the overall argument.
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