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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.

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

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. 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. 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.

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. 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. 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. Simplifying:  When restating the opposition's view, the writer mistakenly ignores information which is relevant to the conclusion reached by the opposition. Presuppositions:  The writer presupposes some information that supports his/her claim;  the writer does not confirm the assumed material. Hiding Information/Half Truth:  The writer, consciously or unconsciously, establishes conclusions without stating all of the facts relevant to the situation.
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.

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

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. Two Wrongs Make a Right:  The writer defends an action on the grounds that someone else has done something similar. 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. Circular Reasoning:  The writer defends the claim by using the conclusion as one of the premises to support the conclusion. 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. 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.
 


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LEO: Literacy Education Online

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Last update: 20 August 1998

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