Today we're going to talk about Fallacies of Vacuity.
An argument suffers from a fallacy of vacuity when the argument doesn't make
any progress, doesn't go anywhere. There are two general ways this can
happen. One way an argument could suffer from a
fallacy of vacuity is when it begs the question.
That is to say, when, in order to believe the premises of the argument, or to
believe that the premises imply the conclusion, we already need to believe
the conclusion. Without already believing the conclusion,
we're not going to believe that it's a successful argument.
That's begging the question. That's one way an argument could suffer
from a fallacy of acuity. Another way an argument could suffer from
a fallacy of acuity is when the conclusion doesn't say anything
substantive. When a conclusion just says, for
instance, well, either it's raining or it's not, something completely
uninformative like that, something that doesn't provide you with any information
that you wouldn't have known independently of the argument.
Those are the 2 general ways in which an argument can suffer from fallacy of
acuity. We'll first talk about begging the
question. Let me start off by giving you a really
simple example of begging the question. It's an example that's so obvious, that
probably none of you would be guilty of this fallacy.
Suppose you're in a strange city, and you're walking around, trying to find
a particular street. And so you go up to a stranger in that
city, a normal seeming stranger. And you ask them for the directions to
this street that you're trying to find. And they say, oh, that street.
that street is three blocks north of here.
And now you think, well, the stranger said that that street is three blocks
north of here. That street is three blocks north of
here. Maybe you believe that because the
stranger said it. And then from those two premises you
conclude So the stranger told the truth. Now let's look at that argument.
That argument has something puzzling about it.
Premise 1, premise 1, the stranger said, the street is 3 blocks north.
[SOUND] Premise (2) The street is 3 blocks north,
[SOUND] where premise two is something you believe, because that's what the
stranger told you. And from those two premises, you draw the
conclusion, the stranger was telling the truth.
Now, notice something funny about this argument?
This argument actually is valid. There's no possible way for the two
premises of the argument to be true, if the conclusion, number three, is false.
If both premises are true then the conclusion has to be true.
So the argument is valid. Furthermore, we can imagine a situation
where the argument is sound, because both of the premises are true.
Right? If you really are walking around a strange city,
and the stranger tells you that the street you're looking for is 3 blocks
north. And, in fact, that street is 3 blocks
north. Then, both of the premises of the
argument are true. And so the argument, in that event, would
be sound. Nonetheless,
the conclusion of this argument is not one that you ought to believe on the
basis of these premises. Now look, you could have all sorts of
good reasons for believing this conclusion, for believing that the
stranger told the truth. For instance, maybe a friend of yours
could vouch for the strangers reliability.
Maybe the stranger has an excellent track record of telling the truth, and people
could tell you about this track record, alright? There could be all sorts of
reasons to believe that the stranger told the truth.
But the point I'm making right now is that these two premises can't be a good
reason to believe that the stranger told the truth, if your reason for believing
the second premise is just that the stranger said that the street was three
blocks north of here. Now why is that? Why can't these two
premises be a good reason for you to believe that the stranger told the truth?
In the situation in which your reason for believing the second premise is just the
truth of the first premise. Here's why.
Suppose the stranger tells you that the street is three blocks north of there.
Well, why should you believe that the street is really three blocks north of
there? Well, you should believe it, just in case
you have a good reason to believe already that the stranger told the truth.
In other words, if you don't already have a good reason to believe that the
stranger told the truth, then you're not going to have a reason to believe the
second premise of this argument on the basis of the fact that the stranger said
that the street was three blocks north of there.
Right? The stranger might have said it, but so what? If you don't have any reason
to believe that the stranger told the truth.
So, if you have a good reason to believe the second premise of this argument, that
the street really is three blocks north of there,
and your good reason has to do with the fact that the stranger said that the
street was three blocks north of there, then that shows that you already have
some reason to believe that the stranger told the truth.
So, if you go and draw the conclussion, the stranger told the truth, that
conclusion, is something that you must of already had a reason to believe.
So this argument can't give you anymore reason to believe it than you already
had. So that's why this argument can't give
you a reason to believe its conclusion even in the case, where the argument is
sound. It might be sound but it's still
ineffective. And this particular kind of
ineffectiveness is one example of what I'll call begging the question.
The argument doesn't make any progress because in order to draw the conclusion
You already have to be justified in believing the conclusion.
In short, you don't learn anything from the argument, you can only draw the
conclusion if you had a good reason for believing the conclusion already.
Now as I said, that example of begging the question is so obvious,
I doubt any of you would be guilty of it or would fall for it.
But let's consider an example of begging the question that's close to something I
actually heard on American television just a couple of months ago.
A friend of American Presidential candidate Mitt Romney said in an
interview that Mitt Romney was going to win the American presidential election.
And his reasoning was that since Mitt Romney never fails in any of his
projects, and since one of his biggest projects ever was to win the American
presidential election, Romney was going to win the American presidential
election. Now consider that argument, that argument
actully was offered by some prominent person on American television.
Premise one. [SOUND] Mitt Romney [SOUND] never fails
[SOUND] in his projects. [SOUND] Premise 2, [SOUND] Romney's
running for President. Conclusion,
[SOUND]
Romney will win [SOUND] the presidency. Now, once again, notice this argument is
valid. If both of the premises are true, then
the conclusion has to be true. Right, if it is indeed one of Romney's
projects to win the presidency, and if indeed he never fails in his projects,
then he will win the presidency. So the argument is valid.
But, is it guilty of a fallacy of acuity? Well, in this particular case, yes.
It begs the question and the reason it begs the question is because whatever
reason you have for believing the first premise of the argument, Romney never
fails in his projects. Whatever reason you have for believing
that must include some reason you have for believing the conclusion that Romney
will win the Presidency. Unless you already have a reason for
believing that Romney will win the Presidency, you can't have a good reason
for believing the first premise of the argument, that Romney never fails in his
projects. So, even though this argument is valid if
there's no possible way for the premeses to be true and the conclusion is false,
nonetheless, the argument does beg the question and so is guilty of a fallacy of
acuity. We've considered a couple examples of
begging the question, but consider yet one more.
Suppose I tell you That God laid down all of his divine commandments in this
pamphlet right here. And you ask me why I believe that.
And I say, well, because the pamphlet. Says that God laid down all of his divine
commandments in this pamphlet right here. And of course, God would not have laid
down his divine commandments in a pamphlet that wasn't wholly true.
So, this pamphlet right here must be wholly true and so must be true, that God
laid down all of his divine commandments in this pamphlet right here.
Now that's an example of begging the question, that is simultaneously an
appeal to authority. That particular argument suffers from
both of the two fallacies that we've described in this lecture and the last.
It is an unjustified appeal to authority, and it begs the question, and I want you
to consider in the exercises that follow which arguments suffer from that same
combination of faults.