Professor Elizabeth Buchanan
Adapted from Gwen Silva & Joanne Chapman
Logical fallacies are errors in reasoning
or defects present in an argument.
These errors make the argument weak
or may even invalidate the argument.
If the argument rests entirely on the
fallacy, then it is determined that the
argument is not worth considering.
The problem with logical fallacies is that they are so
common that they actually sound right.
Since logical fallacies are very persuasive, you, as a
critical reader, must analyze them objectively.
Objectively means: based on facts rather than
feelings or opinions
Note: Like emotional appeals, not all fallacies are
purposely intended to manipulate or deceive.
1) Ad Hominem
Definition: This logical fallacy in Latin literally means ―to
This fallacy can take two forms:
1. attack the person’s personality traits or the events in his or
2. attack the character and reputation of the person because
of individuals he or she associates with (guilt by association).
Watch this video
2) Begging the Question
In this fallacy, the writer asserts to be true an idea that has not
yet been proved to be true.
To beg a question is to argue in a circle, to offer a claim that
assumes the validity of the claim.
In other words, the person making the argument is saying ―This
is true because this is true.‖
This unproven ―truth‖ then becomes the basis of the discussion
Example: ―When did you stop beating your wife?‖
3) False Cause
This fallacy happens when the writer cites something false
or a remote cause to explain a situation
It can also happen when the writer oversimplifies the cause
of a complicated issue.
Example: I failed that last test because I went to a concert the
night before. (The reason this student failed the test was
because he did not study).
False Cause: It rained
because I just washed my car
Washing my car
the rain to come
Ergo Propter Hoc
This fallacy means ―after this, therefore because of this‖ in
It is a type of cause and effect fallacy.
This fallacy suggests that because event B occurred after event
A, event A caused event F.
A connection is made based on chronology.
Many silly superstitions are based on this type of logical fallacy
Example: Yesterday I forgot to wear my special Hawkeye hat during
the annual Michigan-Iowa football game. No wonder Iowa lost.
Post Hoc Big Bang Theory
5) Either-Or Fallacy
Sometimes called false dilemma
Issues are presented with only two alternatives available,
ignoring other possibilities.
Often rejects one choice which requires one to accept the
Example: Bumper sticker in South Dakota: There are
Americans. And then there are liberals.
Pepsi and Coke
Involves ignoring the question by talking around the issue.
This fallacy is similar to Red Herring.
Example: Senator Trueheart is asked in a press conference
whether he supports the American military presence in
Afghanistan. The senator replies: ―I think it’s important to
defend democratic principles. I don’t want to see any
American boys die, but we must defend our precious
liberties that we bought so hard to attain.
(Note: he doesn’t answer the question)
7) False Analogy
An analogy points out
similarities in things
that are otherwise
different. A false
it’s comparing apples
False Analogy Example
If we can put a man on the moon, why
can’t we find the cure for the common
While both things being compared here are related to
science, there are more differences than similarities
between space and biological advancements.
Arguer distorts or oversimplifies
opponent’s argument and then attacks
the distorted argument.
Environmentalists won’t be satisfied until not a single
human being is allowed to enter a national park.
President Bush wants our country to trade with Fidel
Castro's Communist Cuba. I say there should be a
trade embargo against Cuba. The issue in our
election is Cuban trade, and if you are against it,
then you should vote for me for president.
A. ―Those of our people who are forced by
circumstances beyond their control rely on Social
Security and government support such as Aid to
Dependent Children, Food Stamps, etc.—these
victims of an anarchistic economy are now faced
with a second threat to their very existence: their
already minimal benefits are now being reduced by
B. ―A represent naïve liberals who only steal the
taxpayer’s hard-earned money—and throw it away
on the idle. This is robbery—and I oppose it.‖
A self-serving and incorrect reason to account for one’s actions.
It uses reasons that sound plausible but that are actually false,
or at least questionable.
Example: I ate the biggest piece of pie because I didn’t want you to get
Example: I could have finished my paper on time if my printer was
People often come up with excuses and weak explanations for
their own and others’ behavior that often avoid actual causes.
10) Red Herring
An argument that does not offer
reasons to support its conclusion
but diverts attention to other issues
that are irrelevant.
Similar to Evasion Fallacy.
Marijuana smoking is not all that
harmful. I would feel safer in a car
with a driver who has smoked weed
than one under the influence of liquor
Debating a gas tax increase in valuable,
but I really think there should be an
extra tax on SUVs.21
extinct when we
people in our
A RED HERRING CAN ACTUALLY PROVE A
CLAIM; HOWEVER, THE CLAIM PROVEN WILL
NOT BE THE CLAIM THAT WAS ORIGINALLY
Example: Guns are not America’s major problem,
or even high on the list of our problems. Cars,
cancer, accidents in the kitchen all kill far more
people than guns do. It’s not guns that we should
be frightened of but the effects of poverty, lack of
education, a judicial system that sends criminals
and psychopaths back out into the streets. Guns
are not a solution, but they are not the problem,
11) Slippery Slope
An argument that states the conclusion will lead to a
chain reaction of events when there is not sufficient
evidence to support such a chain.
A slippery slope is like an ice covered hill: once you start
down, you can’t stop. The result is likely to be extreme
Ex: Once we allow medical use of marijuana, we’ll legalize it for
everyone, after which we’ll legalize cocaine and heroin.
Ex: We shouldn’t grant citizenship to illegal immigrants now
living the U.S. because no one will want to obey our laws.
Slippery Slope Example
If you permit scientists to destroy human embryos for the
purpose of research, it's a slippery slope from there to
killing human fetuses in order to harvest tissue, and from
there to euthanizing disabled or terminally ill people to
harvest their organs, and from there to human cloning and
human-animal hybrids, and if making chimeras is okay,
well then Dr. Frankenstein must also be okay, and Dr.
Mengele, too, and before you know it, it's one long hapless
inevitable slide from high-minded medicine to the Nazis.
Marty Kaplan, The Huffington Post, March 9, 2009
Optional: View the following YouTube video on Slippery Slope (8:13 minutes)
12) TWO WRONGS MAKE A RIGHT
Argument used to distract attention from a wrongdoing by
claiming that similar actions went unnoticed or
Example: Why bother trying to conserve energy? China is
opening a new coal burning power plant every day. If they’re
not doing their part to prevent climate change, why should we?
Example: So what if I don’t separate the cans and newspapers out
from the garbage for recycling? I don’t have that much time.
Neither do most other people.
The following YouTube video offers a review of
several fallacies and some emotional appeals.
WITH YOUR PARTNER, CREATE AN
ANALOGY ABOUT GUN CONTROL IN
1. false analogy
3. two wrongs don’t make a right
4. red herring
6. slippery slope
Vocabulary List 8
Literature Circle 9
A particular slide catching your eye?
Clipping is a handy way to collect important slides you want to go back to later.