Now we've learned how to identify an argument and put it in standard form.
We've also learned from the definition of argument, that the premises are intended
to be reasons for the conclusion. Great.
Intended to be a reason for the conclusion.
Well intentions are nice, but success is better.
What we need to figure out is when the person succeeds in giving premises that
really are reasons for the conclusion. For simplicity, let's focus on argument
whose purpose is justification. Then the question is, do the premises
justify you in believing the conclusion? Well, imagine that you don't know whether
there's any life on Mars. You have no evidence one way or the
other. Then you ask a friend and the friend says
ha, I know there's life on Mars. I can prove it to you.
Here, this argument will show you that there's life on Mars.
There is at least one bacterium on Mars. Therefore there is life on Mars.
Now notice that if the premise is true the conclusion has got to be true.
And if you and your friend are justified in believing the premise then you and you
are friend are also justified in believing the conclusion.
So this argument looks pretty good so far but of course you have to ask your
friend, well how do you know that there's at least one bacterium on Mars?
And suppose your friend says, well I'm just guessing.
Then the argument is clearly no good. If there's no reason to believe the
premise because your friend is just guessing then you're not justified in
believing that premise. And if you're not justified in believing
the premise then how can that premise make you justified in believing the
conclusion. More generally an argument cannot justify
you in believing the conclusion unless you are justified in accepting the
premises of that argument. Now, suppose your friends says oh, but I
do have a reason for the premise I do then we have to ask what kind of reason
is it? And, at that point your friend needs to
express reason. And, how do we express reasons?
In arguments. So, your friend has to give another
argument for the premise. Where the premise of the first argument
is the conclusion of the second argument. Wait a minute, we got a problem.
Because that second argument is itself going to have premises.
And you have to be justified in believing those.
So the premises of the second argument have to be the conclusion of a third
argument. And so on and so on because the third
argument needs premises. They have to be justified.
So they have to be the conclusion of another argument.
Which also has to have premises. And those have to be the conclusion of
another argument. And so on and so on.
It looks like we've got a real problem here.
In order for the premises to be justified they have to be backed up by an argument,
but the argument has premises of its own that have to be backed up by another
argument and so on, and so on. This problem is called the problem of the
skeptical regress because you regress back to one argument after another, after
another, after another, after another, after another, after another.
And it's hard to see how that regress, is ever, going to come to an end.
There seem to be only three ways to get around this skeptical regress.
The first is to start with a premise that's unjustified.
If it's unjustified, then it doesn't need an argument to back it up.
And that means that you're not going to have this chain of arguments going back
and back and back and back and back and back and back.
The second possibility is to have a structure where the arguments move in a
circle. One claim is justified by another which
is justified by another which is justified by another which is justified
by the first claim. And they just move in a circle.
The third possibility, is that the chain of arguments goes back infinitely.
It never stops. Every claim has an argument to back it
up. And there's no end, so you never have a
prentice which doesn't have an argue to back it up, because it's infinite.
Those seem to be the three main options here to avoid the skeptical regress.
The first possibility then, is to start with a premise that's unjustified.
And that seems pretty neat if you can get away with it but we already saw why that
won't work. We saw your friend arguing that there's
life on Mars because there's at least one bacterium on Mars, and he was just
guessing. If you just guess at your premises, you
have no reason to believe them. Then, an argument that uses those
premises cannot justify you in believing the conclusion.
But in addition, just think about it this way.
You could prove anything if we let you start with unjustified premises.
If you can just make up your premises for no reason then there's no stopping you
from believing whatever, including things that are obviously false.
So it seems to be a real problem to start with premises that are unjustified.
Next, the second way to respond to the skeptical regress is to use a circular
structure. and it's kind of neat, if you think about
it, because, if you want to prove one claim, you prove it on the basis of
another claim. And then you prove that second claim on
the basis of the third, and the third on the basis of the fourth and the fourth on
the fifth, and the fifth on the basis of the first.
And now you've got this circle, and the arguments go in a circle.
But that means that every premise has an argument to back it up.
Cause you can keep going around the circle forever.
You can think about it a little bit, it'll be obvious that that's no good.
And that can be shown by looking at the smallest circle there is.
So suppose your friend says, I can prove there's life on Mars.
Here's my argument. There's life on Mars, therefore there's
life on Mars. Clearly, that's no good.
And the reason why it's no good is that if he didn't know whether there was life
on Mars to begin with, you wouldn't know whether the premise was true.
because if you don't know the conclusion you can't know the premise, since the
premise is the conclusion. So if you're not justified in believing
the conclusion to begin with, you're not justified in believing the premise.
And that means that the argument didn't really get you anywhere.
It just ends up where it started. And in addition, it has the same problem
we saw in the first approach involving unjustified premises.
Because you can use circular arguments to prove anything.
You can prove there's life on Mars there's life on Mars therefore there's
life on Mars. You can prove there's no life on Mars
therefore there's no life on Mars. You can do it either way and the fact
that an argument can be used either way to prove either conclusion suggests
there's a big problem with that kind of argument.
So now we are down to the third and final way to get around the skeptical regress,
and that is to use an infinite chain of arguments.
If you think about it, in a concrete case, you'll see why that's a problem as
well. Suppose your friend says there's life on
Mars and I can prove it. And you say fine, give me a reason?
Well there's a least one bacterium on Mars, therefore there's life on Mars.
And you go okay, fine but how do you know there's a least one bacterium on Mars?
I've got another argument he says, there are at least two bacterium on Mars,
therefore there's at least one bacterium on Mars.
But how do you know there's at least two? Well, there are at least three bacteria
on Mars. Therefore, there are at least two
bacteria on Mars. But how do you know there are at least
three? Well, there are at least four so there
are at least three. Well, there are at least five so there
are at least four. Well, there are at least six so there are
at least five. And so on and so on and so on.
You could go on infinitely. So an infinite chain of arguments.
Would allow you to prove that there's life on Mars even if you have no evidence
whatsoever of any bacteria because you're going to have an argument but if the
premise that you are arguing from doesn't have an independent justification then
the infinite chain is going to be no good at all in justifying the conclusion of
that argument. So many people see this skeptical regress
as a deep and serious philosophical issue.
If the unjustified premise approach doesn't work, and the circular argument
structure doesn't work, and the infinite chain of arguments doesn't work, then
it's hard to see how we can get around the problem.
Which is to say, it's hard to see how any kind of argument could ever justify us in
believing anything. Philosophers really scratched their heads
about that for a long time. And worry about it.
It keeps them up at night. But we're going to have look at how
practical people solve a similar problem in everyday life.
So how we solve this skeptical regress problem in everyday life well there
various tricks which you can use. For example, one way is to just start
from assumptions that everybody shares. So if I say, well you really ought to buy
a Honda because Hondas are very reliable cars.
Then I'm assuming that you want your car to be reliable.
You don't like to have to take it in to the mechanic all the time.
You don't want it to break down on the road.
And if you want reliability and I want reliability, then we can start from the
assumption that reliability's a good thing and that that's a reason to buy a
car that is reliable. But of course you might say, well but our
Honda's reliable. And then I might.
Appeal to an authority. Well, it's obvious that they are.
Or, Consumer Reports has done a study that shows that they're reliable.
And I can appeal to an authority, and if you accept that authority, go, Consumer
Reports, we can trust them, then, my argument's going to work.
You're going to have a reason to believe the conclusion, and it might persuade
you, and make you come to believe the conclusion.
But, suppose that someone is going to raise an objection.
They say, well, Consumer Reports has been wrong before.
They might be wrong this time. Well, then, I need to discount that
objection. I need to respond to it, and say, well,
maybe they have been wrong sometimes, but this time, you know, they've got a good
study and it was careful, or whatever. And the but means, I'm discounting the
objection that you have raised, and I might even discount it in advance.
Well I might just guard my client I might say, well.
They might be right, in this case. Or they're probably right, without
claiming that they definitely are right. So I can assure you by signing as some
kind of authority. I can discount objections and I can guard
my premises by saying, well it's probably right.
Instead of saying that it's definitely right.
And those are three ways of solving. The skeptical regress problem in everyday
life that we're going to look at in much more detail in the next three lectures.
But the point of this lecture has been more general.
In order to solve the skeptical regress problem, you have to find some
assumptions that you and your audience share.
They might be assumptions about the premises of your arguments.
They might be assumptions about authorities that supposedly support your
premises and that they accept as authorities or whatever.
But there have to be some assumptions that you share with your audience in
order to get the argument going. And that's kind of tricky because it's
going to depend on the context. If you are dealing with an audience that
shares a lot of your assumptions that argument is going to be relatively easy.
But if you are dealing with an audience that doesn't share any of your
assumptions it's going to be impossible. And, in areas where there's a lot of
disagreement it's going to be hard to get your argument going because your premises
are going to be questioned and denied or rejected by the people in the audience.
So, what these tricks do, is they give you ways to get the argument going.
But they're not going to work in every case.
And we'll have to look at that, as we're looking at these three different ways to
solve the skeptical regress problem in the next three lectures.