Welcome back. 
In the previous lecture, we saw a 
definition of argument as a connected 
series of sentences, statements, or 
propositions, 
where some of those sentences, 
statements, and propositions are premises 
and one of them is a conclusion. 
And the premises are intended to give 
some kind of reason, for the conclusion. 
In this lecture, we're going to look at 
the purposes for which people give 
arguments, because the purposes are 
crucial in determining what an object is. 
Take for example an artifact that you 
might find at an archaeological site. 
You won't be able to figure out whether 
it's a really big screwdriver or a really 
small spatula, unless you know whether 
the people who used it intended it to 
screw screws, or to pick up food that 
they were cooking. 
So to understand arguments we need to 
understand the purposes for arguments. 
And that means, why does somebody bother 
to give an argument instead of just 
asserting the conclusion without an 
argument? 
Well, just think about it. 
If you went to a used car lot and the 
salesman said, you want to buy that 
Mustang? 
Would that convince you? 
Not a chance. 
But if the salesman said, you want to buy 
that Mustang because it looks really 
cool, and it goes really fast, or maybe 
it has great gas mileage, or whatever, 
and gives you a series of reasons, then 
you might be convinced to buy the 
Mustang. 
So that's one purpose of arguments, to 
try to convince you to do things, or to 
believe things, that you wouldn't 
otherwise do or believe. 
So this purpose is persuading or 
convincing, and if you think about it, 
what the salesman's trying to do is he's 
trying to change your mental states. 
He's trying to make you believe something 
that you didn't believe, or do something 
that you didn't do. 
So he's trying to bring about an effect 
in the world. 
But that's just one purpose of arguments. 
We don't always act like salesmen. 
Sometimes, instead of trying to change 
people's beliefs, we're simply trying to 
give them a reason for their belief or 
for our belief. 
And to give them a reason is not 
necessarily to convince them, or persuade 
them, or change their beliefs. 
When we're simply trying to give them a 
reason to believe the conclusion, we're 
going to call that justification. 
So imagine that your friend, you're not a 
salesman, you're a friend, imagine that 
your friend is thinking about buying a 
car and he doesn't know which one to buy. 
You might say, well, I think you ought to 
buy the Mustang, because it looks really 
good, and it goes really fast, and it's 
actually got pretty good gas mileage, and 
it's quite reliable, or whatever. 
You're not necessarily trying to convince 
her to buy that car. 
It'd be fine with you if she bought any 
car she wanted, 
any car that would make her happy. 
You're trying to talk about the reasons 
for buying the car, so that she can make 
her own decision. 
In that sense, you're trying to justify 
that decision, or that belief that the 
Mustang is the best car for her to buy 
and not necessarily to convince her or 
persuade her. 
If she comes up with great reasons to the 
contrary, you're perfectly happy, 
whereas the salesman wouldn't be. 
But notice, that you might give exactly 
the same reasons that the salesman did. 
Exactly the argument that the salesman 
did. 
The difference lies in the purpose, 
because the salesman is trying to 
convince her to change her beliefs and 
actions. 
But your goal, with your friend is to 
discuss the reasons for her decision or 
action. 
So you're thinking about justification 
and the salesman was thinking about 
persuasion. 
That really matters whether your goal is 
justification or persuasion, because 
there's a big difference here. 
If you're trying to justify your friend's 
belief or your friend's action, 
then you're trying to give her good 
reasons. 
The salesman can convince her or persuade 
her with bad reasons. 
So it doesn't matter to his purposes 
whether the arguments that he gives are 
any good or bad, as long as they work to 
affect that change in the world, 
whereas, you care about whether your 
arguments and your reasons are good 
reasons or arguments, 
because you're trying to justify that 
belief or that action. 
And of course, people can try to do all 
of these things at once. 
They can mix them together in various 
ways and that can get complicated, 
so when someone gives you an argument, 
you need to ask a series of questions. 
The first thing you need to ask is, is 
this person trying to change my mind or 
change my behavior? 
If so, then their goal is persuasion or 
to convince you. 
Then you need to ask, are they trying to 
give reasons for changing my mind or for 
believing if I already believed it. 
Well, if they're doing that then your 
goal is justification. 
And if you go down that series of 
questions, you'll be able to understand 
what the purpose of giving the argument 
is, at least for this range of cases. 
So let's do a few exercises just to make 
sure that you understand justification 
before we go on to the next purpose of 
argument which will be explanation.