LEO: Logic

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Logical Fallacies

When you attempt to employ logic to support claims in your papers, your reasoning is sometimes weakened because you are presenting fallacious arguments. It is important for you to be able to identify and eliminate fallacies in your writing.

This handout will explain and give examples of typical fallacies as divided into five major categories:

The argumentation methods comprising these five categories can be used as rhetorical devices, but they must not be confused with logical thinking. Tutors can help their students to make such a distinction.

FEELINGS

Quite often, writers appeal to their audiences' feelings to attract attention to and elicit agreement with their ideas. Although this can be effective, manipulating audience feelings is not employing logic, and it does not make a writer's argument stronger. Logical thinking never involves feelings.

Appeal to Force: The writer threatens the audience, explicitly or implicitly, with negative consequences if the claim is not believed.

If you do not believe in God, you will go to hell.

Appeal to Pity: The writer begs for the approval of the claim; the audience may agree because they feel sorry for the arguer.

I cannot get a job because the public education system failed me; I have to steal to survive. It is society's fault, not mine.

Appeal to Gallery: The writer uses emotive language that will produce a desired effect on a group or "gallery" of readers. By appealing to the fears or interests of the audience, the writer hopes to gain approval.

Same-sex marriage must be prohibited, or the family structure as we know it will collapse.

Appeal to Authority: The writer cites authorities to show the validity of the claim, but the authority is not an expert in the field, the authority's view is taken out of context, or other experts of that field disagree with the authority quoted.

I think that businesses should not have to limit the amount of pollutants they release into the atmosphere because Rush Limbaugh says that there is no real evidence for industrial pollutants causing the Greenhouse Effect.

Old is Better: The writer relies on traditional wisdom to support the argument. This is a logical pitfall because the argument does not consider that new ideas could apply.

People have believed that fish is "brain food" for decades, so I don't believe the FDA when they claim that eating fish does not enhance the intellect.

New is Better: The writer claims that a new discovery has better effects or is more applicable to a given situation simply because it is new. However, being newer does not make an idea more correct.

Word processed papers are clearer and more error-free than typed papers because they make use of new technology.

DISTRACTION FROM THE ARGUMENT

This type of fallacy often happens when writers do not have strong support for their claims. Distraction is also used if the opposition's view is strong and logical; then, writers have a tendency to attack the context instead of the argument.

Attacking the Speaker: The writer reduces the credibility of the opposition by attacking them personally for who they are and not for what they say. The validity of logical reasoning does not depend on the morality of the speaker.

Oprah Winfrey's diet advice is useless; she has had problems with maintaining her weight for most of her life, bouncing back and forth between being overweight and slender.

Irrelevant Material: The writer introduces irrelevant material to distract the audience from the subject at hand. Then, s/he draws conclusions based on the unrelated material presented.

Education is important for the future of the American people and our country. So, you should choose to study at St. Cloud State University.

Shifted Burden of Proof: The writer challenges those with an opposing view to defend their arguments; this puts the writer in a position in which s/he can deny the opposition's assertions.

The author writes that animals shouldn't be killed because they can feel pain, but he doesn't prove that they can. For his argument to persuade me, he has to give me positive empirical evidence of animals' ability to feel pain.

Straw Man: The writer does not attack the argument that the opposition sets forth. The arguer may attack one of the opposition's points as if it were the whole argument, distort what the opposition is attempting to express, or exaggerate the opposition's argument to the point of satirizing it.

MISINFORMATION

Sometimes, writers present questionable or ambiguous reasons to sustain their arguments. A logical demonstration of a belief, however, must be conclusive and convincing to be effective; any doubtful premises leads the audience to believe that the conclusion is weak.

From Ignorance: The writer's argument is simply that the point has not been proven otherwise. The fact that the counterclaim has not been proven does not make a claim correct.

I believe in God because no one can prove that a god doesn't exist.

False Cause: The writer points out as the cause of an event something that is not the actual cause, or the writer has insufficient evidence for making a causal link. If the identified cause is not the real cause, nothing assures that the point of discussion is true.

Bush was "determined to knock down Saddam Hussein" because of his "nuclear bomb potential."

Note: Hussein did not have any nuclear weapons.

Questionable Premises: The writer's reasons for holding a belief are not as obvious to the audience as they are to the writer, and the writer does not back up the claim with enough support. This fallacy also occurs when the writer introduces an unsupported value judgment.

All judges are fair-minded individuals; therefore, Judge Ito is fair in his decisions.

Ambiguity of Terms/Equivocation: The writer uses two different senses of the same word in an argument, and this ambiguity allows a mistaken conclusion to be drawn by the writer.

It is immoral to kill an innocent human being. Fetuses are innocent human beings. Therefore, it is immoral to kill fetuses.

Note: In the first sentence, the writer uses "human being" in the sense of a morally considerable being. In the second, the writer could be using the term "human being" to make the less controversial claim that a fetus is a genetically human creature.

Simplifying: When restating the opposition's view, the writer mistakenly ignores information which is relevant to the conclusion reached by the opposition.

Freud argued that women have penis envy because they want to be men.

Presuppositions: The writer presupposes some information that supports his/her claim; the writer does not confirm the assumed material.

All students who study on this campus want more computers available for their use, so computer fees should be raised 50% to cover the costs of the expansion.

Hiding Information/Half Truth: The writer, consciously or unconsciously, establishes conclusions without stating all of the facts relevant to the situation.

The Geo Metro is a superior car because it averages 43 miles per gallon.

Note: The writer neglects to mention that this figure was derived in tests where the car was driven with 30 mile per hour tailwinds.

GENERALIZATION

Some writers stereotype and generalize their ideas to make a powerful statement. To construct effective logical arguments, writers must avoid generalizations; once an exception to a generalization is found, the argument that the generalization supports is discredited.

Popularity: The writer bases the argument on the belief that if an idea is held by a large group of people, it is true.

Millions of people are Marxists, so Marxist economic and political theories are correct.

Exception: The writer applies a general rule to a case where the rule is inapplicable.

A year is 365 days long, so I celebrate my birthday every 365 days.

Particular Experiences: The writer makes a rule out of particular experiences to support the claim. As soon as an exception to the derived rule is found, the rule fails to support the argument.

All Greek food causes illness; when I traveled through Greece, I got food poisoning.

Property in the Whole: The writer makes a claim based on the belief that a whole always possesses the characteristics of its parts, which is often untrue. Although this belief is sometimes acceptable, it is not universally applicable, so the appropriateness of using this idea must be determined on a case by case basis.

Since many of the students at St. Cloud State University get A's, St. Cloud State must be a top-rated school.

Property in the Parts: Often, a writer who makes the above fallacy will also commit this one. The writer erroneously assumes that because a whole has a particular property, the parts forming the whole have the same property.

IBM is a reputable organization, so all of its employees must be reputable.

False Alternative: The writer only presents some of the alternatives for solving a problem when more possibilities exist because the writer assumes that the list of alternatives created is exhaustive.

IRRELEVANT CONNECTIONS

Some writers' arguments fail not because of the information given, but because of the type of connections established between the parts of the argument. If the logical structures are not valid, the argument will fail, even if all of the premises are true and correct.

Consecutive Relation: The writer assumes that because two events occur consecutively or concurrently, they are causally related.

I believe in supernatural beings because every time I drive past the cemetery where my grandmother is buried, a light on my dashboard flashes. Her spirit causes this because it never happens otherwise.

Slippery Slope: The writer bases the claim on the assumption that if a particular event occurs, so will other undesirable events. However, there are no reasons to believe that the subsequent events will occur. This fallacy is usually caused by fear.

If we put limits on the right to bear arms, soon all of our Constitutionally-given rights will be taken away.

Two Wrongs Make a Right: The writer defends an action on the grounds that someone else has done something similar.

Residents of St. Cloud should not have to recycle plastics because those who live in Waite Park are not required to.

Wrong Analogy: The writer reasons by analogy, using a similar, known situation as the basis for the argument. Extended analogies tend to lose their direct connection with the actual topic of discussion, leading to erroneous conclusions.

Having a television rating system is like being in prison. Both infringe on one's rights.

Circular Reasoning: The writer defends the claim by using the conclusion as one of the premises to support the conclusion.

God exists because the Bible says so. The Bible is a reliable source because it is the word of God.

Affirmation of the Consequent: The writer uses an If...then statement in the argument's reasoning. Then, the writer confirms the then part of the statement and derives the If part, thereby committing a serious logical flaw.

If one is 16 years old or older, one can drive an automobile in Wisconsin. I saw your niece driving through Wausau yesterday. She must be at least 16.

Denial of the Antecedent: Again, the writer employs an If...then statement, but in this case, the writer denies the If part so that the negation of the then part can be concluded. However, just because the If part does not happen, it does not follow that the then part will not happen. The then part could result for some other reason.

Sources

Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life. 7th ed. Belmont, CA: Wadsworth, 1971.

Pitt, Jack. Logic for Argument. New York: Random House, 1968.

Woodhouse, Mark B. A Preface to Philosophy. 5th ed. Belmont, CA: Wadsworth, 1994.

This page was created by Maggie Escalas, Julie Feia, and Carrie Jean Schroeder, St. Cloud State University, St. Cloud, MN; it may be copied for educational purposes only. If you copy this document, please include our copyright notice and the names of the writers; if you revise it, please add your name(s) to the list of writers.

Last update: 20 August 1998

URL: http://leo.stcloudstate.edu/acadwrite/logic.html

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