In this video I'd like to address some common logical fallacies. By the word
"fallacy" we mean a mistake. So these are mistakes in reasoning. And there are
quite a few of them, but we're just going to restrict ourselves to some of the more
common ones. The first example here reads,
"Professor Karl Knutson has recently argued that all coffee drinking in
public places should be banned. Knutson believes that coffee is an
addiction and that all addictions are evil." What we have here is in some
ways a strawman argument ... and the idea is that if you
summarize an opposing view in such a way that it's not a fair summation, that it's
more of a caricature, then you're guilty of using a strawman argument. And you
can see here that by saying that Knutson believes that all
addictions are evil -- these are very strong words. They're very general. Maybe
Knutson doesn't believe his position quite that strongly. So in that case we
are guilty of using a strawman argument. The second one reads, "It is Knutson who
is evil. Did you know that he divorced his wife just because of her coffee
breath?" In this case what we have is what's called an ad hominem argument ...
ad hominem ... and you'll see that a lot of these mistakes have Latin names. This
one here literally in Latin it means "to the man." This mistake is where you
attack the person as opposed to the issue or the view. Sometimes that may be
legitimate, for instance if you're in a courtroom and you're trying to discredit
a witness. But most often in public discourse that's not appropriate, and you
should really try to stick to the issue. The third one reads, "But then it's
typical of a Swede to think only in absolutes," and so on. Now this one is an
example of stereotyping ... where we generalize about a particular
group of people or a particular issue. I don't think I have to explain too
much about what this is, but it is something to watch out for. Number four
reads, "If you love coffee, however, then you'll
agree with me that Knutson should be roasted for his views." This is what we
might call a non sequitur ... another Latin title.
Literally this means "it does not follow." It's also the title of a comic strip by
the way which is quite funny. So the idea here is that if we have A and we say it
leads to B, but the logic is not quite there, then we're dealing with a non
sequitur, something that does not follow from something that came before.
Number 5 reads, "Either coffee is an addiction or it is the most liberating
beverage on earth." And here we have what's called an either-or fallacy.
Either it's this or it is that. We tend to do this more
often, where we just give two alternatives or two options where there
may actually be more, and we shouldn't restrict ourselves too much. Number 6
reads, "After I turned 18 and began drinking 6 cups a day (in my teen
teenage years I limited myself to 4), my productivity soared," and so on. This is
called a post hoc argument. Post hoc is short for a
longer Latin phrase which goes "post hoc ergo (ergo means therefore) propter
hoc," and "propter" means "because" and "hoc" means "this." So literally this means "after
this therefore because of this." Sounds very complicated, but it's actually
fairly straightforward. If you have event A and you have B, and B happened some
time after event A then you might suppose that A has caused B, but that's
not necessarily the case. Just because one thing happens after another
doesn't mean that A has caused B. So that's a post hoc
fallacy. Then we have 7, which reads, "So join me in the fight for public coffee
consumption. If we don't fight for the right to drink an espresso or cappuccino
we may soon lose our privileges." This is a slippery slope
argument. The idea is fairly simple. Think of a slope and if
you start with something, if you give in, and, you know, you say "well this is
okay" then the ball starts rolling and you end up further down the
slope. So slippery slope arguments may have some validity sometimes, but on the
whole you should watch out for them. And then the last one here reads, "Fortunately
Knutson hasn't reckoned with the fact that many of us are willing to make a
stand. If enough people speak up then Knutson will know once and for all that
he is in the wrong." This last one here is a bandwagon appeal.
The idea is that if you jump on the bandwagon, if you join popular
opinion, then you may think you're right, but it's not necessarily the case that
the majority of the people (or many people who are fashionable and popular)
are necessarily correct. Okay, so those are some of the most common fallacies we
have in logic and in rhetoric, and those are ones definitely to watch out for.