logical fallacies

Mr. Hartnett
Christian Ethics
The points below are addressed principally to those engaged in a classroom debate or
discussion.
The points would also prove helpful to anyone who will present a speech before an
audience; however, the material is generally applicable to papers as well, especially
those that seek to argue for a particular position.
Logical Fallacies: A logical fallacy is an error in reasoning. Logical fallacies should be
avoided in ethical debates and discussions.
Key Terms
· Argument: A conclusion together with the premises that support it.
· Premise: A reason offered as support for another claim.
· Conclusion: A claim supported by a premise.
· Valid: An argument whose premises genuinely support its
conclusion.
· Unsound: An argument that has at least one false premise.
· Fallacy: An argument that relies upon faulty reasoning.
· Booby-trap: An argument that, while not a fallacy itself, might lead
an inattentive reader to commit an error.
Red Herring: A fallacy that introduces an irrelevant issue to divert attention from the
subject under discussion.
Example: “Why do I need to follow the school dress code when the school can’t even fix
the computers in the computer lab?”
Analysis: Broken computers in the computer lab are a problem, but it has nothing to do
with a student following the dress code. It is a red herring.
Ad Hominem: A fallacy that attacks the person rather than dealing with the real issue
in dispute.
Example: “John may have some good arguments in favor of a flat tax but let’s not forget
his parents drive expensive cars and live in a big house.”
Analysis: Instead of dealing with the substance of John’s arguments, the speaker attacks
John’s wealth, which has nothing to do with the merits of his argument.

Either – Or: A fallacy that forces listeners to choose between two alternatives when
more than two options exist. It is usually a false dilemma.
Example: “Either we raise taxes to pay for social security, or millions of senior citizens
will lose their only source of income.”
Analysis: Raising taxes is only one option to pay for social security. There are also
plenty of other options as well.
Band Wagon: A fallacy that assumes that because something is popular, it is therefore
good, correct, or desirable.
Example: You walk into a Toyota car dealership, and the salesman says, “More people
drive Toyotas than Hondas; therefore, Toyota must make a better car.”
Analysis: Just because more people drive Toyotas than Hondas does not mean Toyotas
are better. It may be that Toyota has a better marketing campaign.
Slippery Slope: A fallacy that assumes that taking the first step will lead to
subsequent steps that cannot be prevented.
Example: “Once the government passes a law restricting violence on TV, it will be the
first step towards complete censorship in this country. Before you know it, the
government will have full control over the media, and there will be no outlet for free
expression left.
Analysis: It is not fair to assume later steps will occur without evidence.
Non Sequitur: A fallacy that occurs when one claim doesn’t follow from the other.
Example: “John should become a sports writer. He loves to play catch with the
baseball in his backyard.”
Analysis: what is presented as evidence or reason is irrelevant or adds very little support
to the conclusion
The argument from Dubious Authority: A fallacy that occurs when a speaker
supports an argument with an authority whose expertise lies outside the issue.
Example: A sports athlete testifies in a commercial about the outstanding quality and
reliability of Chevy trucks.
Analysis: What does a sports athlete know about engineering and building a truck? He
is out of his element.
Post Hoc Ergo Propter Hoc: A fallacy that assumes a cause and effect relationship
exists just because one event follows or coincides with another.

Example: Between 1990 and 2000, gun ownership increased in the United
States. During that same period, crime decreased in the United States. Therefore,
increased gun ownership causes a decrease in crime.
Analysis: While increased gun ownership may cause a decrease in crime, there is no
direct evidence that one causes the other. Correlation does not mean causation. There
are thousands of other factors that may have played a far more critical role in decreasing
crime. Perhaps the economy was doing better than average or maybe state governments
across the country were doing a better job of preventing crime with new police tactics.
Begging the Question: A fallacy that occurs when the conclusion’s truth is assumed
in the premise.
Example: We know God exists since the Bible says God exists. And we know what the
Bible says is true because God wrote it.
Analysis: the argument's premise assumes the truth of the conclusion instead of
supporting it.
Genetic Fallacy: rejecting an argument based on its origins rather than on its own
merits. A related form accepts or rejects ideas based on others who endorse or reject
those same arguments.
Example: You think labor unions are good? Do you know who else liked labor unions?
Karl Marx, that’s who.
Analysis: The argument rejects labor unions because Marx supported them
Straw Man: A fallacy that occurs when a speaker attacks an argument, which is
different from and usually weaker than the opponent’s best argument.
Example: The government should outlaw guns. The opposition opposes this measure
because they fear the deer population will grow out of control. However, the opposition
needs to realize that there are more important issues than the deer population. Guns
are destroying our cities.
Analysis: The opposition might be slightly concerned with an out of control deer
population but is hardly their best or most important argument against banning guns.
Vagueness (booby-trap not fallacy): A lack of clarity or precision in language.
Words or groups of words are vague when their meanings are inexact or unclear to
which things the word or words apply.
Example: Your horoscope today: Small talk sometimes makes the world go 'round. A
casual conversation at work or at a dinner party can spark something much greater than
the sum of its parts. Go ahead and talk to multiple people about many things.

Analysis: What does it mean for a conversation to “spark something much greater than
the sum of its parts”? It could tell just about anything, making the prediction true but
relatively empty
Equivocation: A subcategory of vagueness consists of using a term or expression in an
argument in one sense in one place and another sense in another.
Example: Any law can be repealed by the proper legal authority. The law of gravity is a
law. Therefore, the law of gravity can be repealed by the appropriate legal authority.
Analysis: The word “law” is being used in two different senses.