We've looked at some examples of 
unjustified ad hominem arguments, and 
we've looked at some examples of 
unjustified appeals to authority. 
Now, all of those arguments, the 
unjustified ones, are examples of 
fallacies of relevance. 
And because they're fallacies, they're 
bad arguments. 
Now, remember I said, at the beginning of 
the lecture on fallacies of relevance, 
that a fallacy of relevance could still 
have some other good qualities of an 
argument. 
So, for instance a fallacy of relevance 
could be valid. 
It could be an argument where there is no 
possible way for the conclusion to be 
false if the premise is true. 
Now I'd like to give you an example of a 
fallacy of relevance that is nonetheless 
valid. 
Consider something very strange that I 
just saw the other day. 
Speaker: You know why I'm so nervous? 
Because I've got a nervous system, I 
assure you I have a nervous system. 
Speaker: Now suppose, after seeing what I 
just saw, I made the following argument, 
which is an appeal to authority. 
I say. 
Walter offered his assurance that he has 
a nervous system. 
And from that premise I draw the 
conclusion that Walter has a nervous 
system. 
That looks like an appeal to authority. 
He offered his assurance that he has a 
nervous system So you must have a nervous 
system, right? Well if that argument is 
an appeal to authority, it's unjustified. 
And the reason why it's unjustified is 
that even thought Walter thinks that he 
has a nervous system, his merely thinking 
it Doesn't gaurantee that he's right, 
does it? Trick question. 
Trick question. 
Because nothing, in fact, can offer it's 
assurance that it has a nervous system, 
unless it really does have a nervous 
system. 
Consider, for instance, Walter's 
mechanical toy parrot, Sebastian. 
Whenever Sebastian hears Walter say 
something at a certain volume, Sebastian 
repeats back whatever it is that Walter 
said. 
So, when Walter says, I have a nervous 
system, in Sebastian's presence, 
Sebastian repeats back I have a nervous 
system. 
Now even though Sebastian repeats back, I 
have a nervous system. 
Sebastian isn't offering its assurance 
that it has a nervous system. 
It's just a mechanical toy parrot. 
So it's making sounds to the effect that, 
it has a nervous system, but it's not 
offering its assurance, about anything. 
A mechanical toy parrot doesn't have any 
assurance to offer. 
It's also true, that a mechanical toy 
parrot, doesn't have a nervous system. 
So, this argument here, while it might be 
valid, is nonetheless, i fallacy of 
relevance. 
It's an unjustified appeal to authority. 
Nonetheless, perhaps unbeknownst to the 
person who makes the argument, it is 
valid. 
There is no possible way for the premise 
to be true if the conclusion is false. 
Now I realize this may be hard to 
believe, 
but recently, over recent generations 
that is, pigs have been evolving to 
acquire opposable thumbs. 
And given the general level of porcine 
intelligence, this could mean a complete 
reshaping of the planet. 
Speaker: Trust me, I am not lying about 
this. 
This is for real. 
Speaker: Hmm. 
Well, Ron said he wasn't lying. 
So I guess pigs are developing opposable 
thumbs. 
Speaker: Now the reasoning that you just 
saw Anthony do might have looked simple, 
but actually it involved 2 steps. Let's 
analyze those steps. 
First, he heard me say that I was not 
lying when I said that pigs are evolving 
opposable thumbs. 
So from the premise that I said I was not 
lying, 
when I said pigs were evolving oposable 
thumbs, Anthony concluded that indeed I 
was not lying when I said pigs are 
evolving oposable thumbs. 
I noticed that first step in reasoning is 
an appeal to authority. 
Anthony is appealing to my authority, 
when I said that I was not lying, because 
I said I was not lying, Anthony concludes 
that I was not lying. 
But now consider the second step of his 
reasoning. 
From the premise that I was not lying 
when I said pigs are evolving opposable 
thumbs, Anthony drew the conclusion that 
pigs really are evolving opposable 
thumbs. 
But that, is another appeal to authority. 
From the fact that I was not lying when I 
said pigs are evolving opposable thumbs 
all that follows is that I really believe 
that pigs are evolving opposable thumbs. 
It doesn't yet follow that pigs really 
are evolving opposable thumbs. 
Am I someone who knows what I'm talking 
about when I talk about porcine 
evolution? If not, then this second step 
in reasoning is not justified, it's an 
unjustified appeal to authority. 
Simply because I believe that pigs are 
evolving oposable thumbs doesn't mean 
that they really are. 
So in the apparently simple reasoning 
that we just saw Anthony perform, there 
were really 2 steps, and each one of 
those steps was itself an unjustified 
appeal to authority. 
See, appeals to authority can be very 
tricky. 
They can go past without our even 
noticing.