As I said in the first lecture, arguments 
are used for many purposes. 
And, in the lecture just before this one, 
we saw that it can be used for persuasion 
and also for justification of various 
sorts. 
But persuasion and justification are not 
the only purposes for which arguments are 
given. 
Arguments are also given in order to 
explain things. 
So, we're going to spend this lecture 
talking about explanation. 
Indeed, what we're going to try to do is 
to explain explanation. 
We explain things all the time, 
and I'm going to give an example that'll 
probably really tick off my co-teacher 
wrong, because he's from Chapel Hill. 
But, 
my example, somebody might ask, why did 
the Duke basketball team win the national 
championship in 2010? 
The answer might be that they had great 
players, and a great coach, and, of 
course, they got lucky. 
you have to have some luck to win a 
national championship. 
But, in any case, an explanation of that 
event is a reason why it happened. 
so to explain something is to give a 
reason why it happened or to answer a 
question about why it happened. 
Notice that when you explain something, 
you assume that it's true. 
It wouldn't make any sense to ask, why 
did Duke win the national championship in 
2011? 
because they didn't. 
You can only ask why this thing happened 
if it happened. 
So, we've already got one difference 
between explanation, and justification, 
and persuasion. 
When you try to persuade someone to 
believe something, that thing doesn't 
have to be true and they don't have to 
have believed it in advance. 
When you justify something, right? You 
can justify belief in something that they 
don't already believe. 
But when you explain something, both the 
arguer and the audience are assuming 
that, that thing happened, that the 
conclusion is true, and they're looking 
for the reasons why it happened. 
So, if the goal of explanation is not to 
persuade or to justify and the arguer and 
the, and the audience both already 
believe the conclusion, then what's the 
point? 
What's the goal of explanation? 
The goal of explanation is to increase 
understanding. 
Not to convince us that the conclusion is 
true, but to help us understand why its 
true. 
And we can do that in a number of 
different ways. 
Their actually, 
according to Aristotle, four different 
types of causes, he would call them, but 
we would probably call them explanations. 
The first, were, he called efficient 
causation, we'll just call it causal 
explanation. 
And that tells you why something happen. 
Why did the bridge collapse? 
Because there was an earthquake, that 
explains why the bridge collapsed. 
The second type of explanation, he called 
teleological or purposeful explanation 
because it's looking at the purpose or 
the telos or the goal. 
Why did Joe go to the grocery store? 
To buy milk. 
His goal of buying milk is what explains 
why he went to the grocery store. 
Third type of explanation is formal. 
Why does this peg not fit into this hole? 
And the answer is, because the peg is 
square and the hole is round. 
That's why it doesn't fit in the hole and 
that explains it. 
It helps you understand why it didn't 
fit. 
The fourth kind of explanation is 
material. 
Why is this golf club so light? 
Why's it weigh so little? 
The answer might be, because it's made 
out of graphite. 
That helps you understand why the weight 
is so low on this golf club. 
it would be a lot heavier if it were made 
out of steel. 
So, we can have four different types of 
explanation. 
We can have causal, we can have 
teleological, we can have formal, and we 
can have material. 
And all of those different types of 
explanation are aimed at helping us to 
understand why something happened. 
So did you hear that train whistle? 
We want to ask, why does the train emit 
such a loud noise? 
Well, one answer might be that what 
causes it to make that noise is that the 
conductor pull lever on the train which 
creates that noise. 
That would be a causal explanation. 
Another explanation might be the 
teleological explanation. 
The train was crossing an intersection 
with cars and wanted the cars to know 
that they're coming. 
Another explanation might be a formal 
explanation. 
Because the whistle on the top of the 
train has a certain shape that makes the 
air come out with a certain vibration. 
And a final explanation might be, a 
material explanation. 
Because air has a certain density and a 
certain material that makes it create 
that kind of sound. 
So, we can give all four types of 
explanations for the same event. 
Here's another example where we can apply 
all four types of explanation to a single 
event. 
Joe jumped out of an airplane, that's 
what caused him to fall. 
But then, why did he jump out of the 
airplane to get excitement? 
Why did he fall so fast, because of his 
shape, it was aerodynamic, and because of 
the material that he was made out of, 
heavy flesh, which was a lot denser than 
the surrounding air. 
So, all four of the factors go into an 
explanation of why Joe fell when he 
jumped out of the airplane. 
So next we need to talk about the forms 
of explanation. 
You can actually give explanations in, in 
several different forms. 
For example, if somebody says, why did 
you move to Duke? 
I might tell a story about things that 
happened before I moved to Duke that led 
me to want to move to Duke and I could 
talk about moving to Duke and, and all 
the nice people here and so on. 
You can give explanations in the form of 
narratives like that. 
But notice that, that's not going to 
imply that everybody in similar 
circumstances is going to behave in 
exactly the same way. 
So, you're not going to get general 
principles out of those types of 
narrative explanations. 
But other explanations are given in the 
form of arguments, 
and that's the kind that we're going to 
be interested in here. 
The form in which explanations occur in 
arguments is really pretty simple. 
One premise usually states some kind of 
general principle that can apply to a lot 
of different situations. 
And then, the second premise talks about 
the current situation and says that those 
types of features that the principle 
mentions are instantiated in this case. 
And then the conclusion says, that 
explains why it happened this way in this 
case. 
For example, 
if we want to know why objects fall, 
right? 
So, there's a book and it falls, if we 
want to explain that, we need to cite a 
general principle. 
But notice that not all objects fall, 
some objects actually rise, helium 
balloons rise. 
So, we need a principle that's going to 
explain why some objects fall, and other 
objects rise. 
Then, we'll understand why helium 
balloons rise, just to stick with that 
example. 
And the answer is that, when an object is 
suspended freely in a medium where the 
medium is more dense than the object, 
then it rises. 
And when an object is suspended freely in 
a medium where the object is more dense 
than the medium, thent if falls. 
So, you can explain why helium balloons 
rise by having as your first premise, 
whenever an object is sus, freely 
suspended in a medium, like a gas or a 
liquid, 
and the medium is more dense than the 
object, then object rises. 
Now, let's talk about the circumstances 
in this particular case. 
The helium balloon is less dense than the 
air that surrounds it, 
therefore the helium balloon rises. 
And that explains why the helium balloon 
rises, and you can see how you'd give 
another argument to explain why the book 
fell. 
Now, this form of argument gives some 
people the impression that any 
generalization can be used for 
explanation. 
But that's not quite right. 
One example is Bode's Law. 
Bode's Law says that 0.4 + 0.3 * 2 to the 
n can be used to predict all the 
distances between planets and the sun, 
where n is the number of the planet. 
So, if n is Venus, the n is zero. 
Earth is one, Mars is two, and so on. 
this law was actually used to predict 
both the largest asteroid in the asteroid 
belt, Ceres, and also Uranus. 
So, this law is a generalization that 
held for all the planets that they knew 
in Bode's day and also used to predict 
new observations of planets. 
Pretty cool. 
It actually turns out to fail when you 
get to other planets in, including 
Neptune and Pluto. 
But, 
still it worked pretty well for the data 
that they had. 
But nobody thought that this law 
explained why the planets were that far 
from the Sun. 
They happened to fall in that pattern. 
It could be used to predict, but it 
didn't explain why they were the distance 
they actually were from the Sun. 
So, Bode's Law gives you a nice example 
where you can have a generalization and a 
prediction without explanation. 
Now, here's an example where you can have 
explanation without prediction. 
Just think of a woman who has AIDS and 
gets pregnant and gives birth and her 
child has AIDS, too. 
Now, that would explain why the child was 
born with AIDS. 
But, it won't predict that the child will 
get AIDS because actually, less then 50% 
of the children who are born to mothers 
who have AIDS, have AIDS themselves. 
So, you can't get a prediction out of 
that disease state, 
but you can get an explanation when the 
child does, in fact, have AIDS. 
And notice also, that the fact that the 
mother has AIDS doesn't justify you in 
believing that the child has AIDS. 
What justifies you in believing that the 
child has AIDS is that you test the 
child's blood and find HIV in the blood. 
So, here we have an example where there's 
an explanation without justification or 
prediction. 
And so, explanation is very different 
from those other uses of argument. 
So then, more positively, what is the 
goal of explanation? 
Well, the goal of explanation is to fit 
this particular phenomenon into a general 
pattern. 
And, that's what all of these 
explanations do. 
Why do you want to fit them into a 
general pattern is simply to increase 
your understanding of why they came 
about. 
They came about because they fit into 
this particular type of pattern. 
And this kind of understanding them, 
fitting them into a well known pattern, 
is useful. 
Because most of the things that we want 
to explain are kind of weird, unusual, 
bewildering, surprising phenomenon. 
That's when you need an explanation. 
Because fitting into the pattern makes it 
a little less bewildering, a little less 
surprising because it shows that it's 
kind of like other things that have 
happened before. 
And that's what Bode's Law does not do. 
Because Bode's Law, although it holds for 
all the planets that had been observed in 
the day of Bode, it doesn't explain 
anything else. 
It doesn't fit it into a larger pattern 
with other planets around other solar 
systems. 
And now that we've discovered planets, 
we've found many planets around other 
stars that don't seem to follow Bode's 
Law at all. 
So, it doesn't fit our solar system into 
a general pattern. 
And that's why even though it's a 
generalization and was used to predict 
other planets, it does not provide an 
explanation of why the planets are 
certain distances from the Sun. 
So now, we've learned a little bit about 
what explanation is and what explanation 
is not. 
Explanation is an attempt to fit a 
particular phenomenon into a general 
pattern in order to increase our 
understanding of why it happened, and to 
remove bewilderment or surprise. 
Explanation is not persuasion, or 
justification, or generalization, or 
prediction. 
Those are other uses of argument. 
So, we've seen quite a variety of 
different uses of argument, but we've 
only scratched the surface. 
There can be lots more, and lots more to 
say about each of these. 
So, if you want to learn more about these 
purposes of argument, a good place to 
start would be chapter one of the 
accompanying text, understanding 
arguments. 
But we're going to leave this topic for 
now, and turn to a separate topic. 
In order to understand something you want 
to know, not just its purpose, but the 
material out of which it's made. 
So, the next few lectures will be about 
the material out of which arguments are 
made namely, language.