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Logical fallacy summary
Latest revision as of 10:46, 2 October 2011
A logical fallacy is a statement that is made appearing or claiming to be truthful or accurate, but due to an error in the structure of the claim, is not necessarily truthful nor accurate.
Unfortunately, logical fallacies are rampant in mainstream media. Being aware of the various types of fallacies and how they are structured, can help you identify misleading statements and recognize what is and isn't legitimate information.
Fallacies of Distraction
These fallacies depend upon distracting or confusing the person.
- two choices are given when in fact there are three or more options.
- If you're not with us, then you're with the terrorists
- because something is not known to be true, it is assumed to be false
- Have you ever seen a zombie?
- 'There is no such thing as a black swan because none has ever been observed.'
- a series of increasingly unacceptable consequences is drawn
- If we allow cannabis to be decriminalized, they'll be legalizing heroin next!
- two unrelated points are conjoined as a single proposition
Appeals to Motives in Place of Support
These fallacies prey upon peoples' emotions.
Appeal to Force
- the reader is persuaded to agree by force
Appeal to Pity
- the reader is persuaded to agree by sympathy
"How can you say that ball was out of bounds? It was so close, and I'm down ten games to two"
"You always win these arguments. Can you just let me win once?"
- the reader is warned of unacceptable consequences. This is pretty much a constant logical fallacy upon which most religion is based.
This can include concepts such as "they'll move on to much bigger targets than just the twin towers at 9/11 if they're not stopped" to persuade viewers.
- value or moral goodness is attached to believing the author
- a proposition is argued to be true because it is widely held to be true
- If God wasn't real, why would the vast majority of people believe in God?
Changing the Subject
These fallacies also distract the person by bringing up something not necessarily related to the subject at hand.
Attacking the Person (Ad Hominem)
- the person's character is attacked, the person's circumstances are noted, the person does not practise what is preached
Appeal to Authority
- the authority is not an expert in the field, experts in the field disagree, the authority was joking, drunk, or in some other way not being serious
- the authority in question is not named
Style Over Substance
- the manner in which an argument (or arguer) is presented is felt to affect the truth of the conclusion
- once a question has been answered or an argument made, the criteria for answering is suddenly changed
A claim is made that is not fully-justified.
- the sample is too small to support an inductive generalization about a population
- the sample is unrepresentative of the sample as a whole
- the two objects or events being compared are relevantly dissimilar
- the conclusion of a strong inductive argument is denied despite the evidence to the contrary
Hugo has had twelve car accidents in the last six months, yet he insists that it is just a coincidence and not his fault. (Inductively, the evidence is overwhelming that it is his fault.)
Fallacy of Exclusion
- evidence which would change the outcome of an inductive argument is excluded from consideration
Fallacies Involving Statistical Syllogisms
A Syllogism is a claim that is based on the combination of two prior claims. Using statistics, one can easily manipulate data to make erroneous claims.
- a generalization is applied when circumstances suggest that there should be an exception
- an exception is applied in circumstances where a generalization should apply
A dubious/erroneous cause-and-effect relationship is claimed.
Post Hoc Ergo Propter Hoc
- because one thing follows another, it is held to be caused by the other
- one thing is held to cause another when in fact they are both the joint effects of an underlying cause
- one thing is held to cause another, and it does, but it is insignificant compared to other causes of the effect
- the direction between cause and effect is reversed
- the cause identified is only a part of the entire cause of the effect
Missing the Point, Distraction
Someone goes off topic, partially as a distraction and partially to cover up the fact that they're injecting something not directly related to the subject at hand, using it as phony "evidence."
Begging the Question
- the truth of the conclusion is assumed by the premises
- an argument in defense of one conclusion instead proves a different conclusion
- the introduction of additional, often unrelated information or commentary as a means of avoiding the principal argument
- the author attacks an argument different from (and weaker than) the opposition's best argument
Fallacies of Ambiguity
These are methods of presenting claims which, due to the nature of their delivery, are misleading or erroneous.
- the same term is used with two different meanings
- the structure of a sentence allows two different interpretations
- the emphasis on a word or phrase suggests a meaning contrary to what the sentence actually says
These are false claims.
- because the attributes of the parts of a whole have a certain property, it is argued that the whole has that property
- because the whole has a certain property, it is argued that the parts have that property
These are unsupported and presumptuous conclusions.
Affirming the Consequent
- any argument of the form: If A, then B. B; therefore A
- All Italians eat spaghetti, so anyone who eats spaghetti is Italian.
Argument By Question
- a false assumption is introduced in the form of an interrogative
- Have you stopped beating your wife?
- (this assumption can't be denied by answering simply "yes" or "no".)
Denying the Antecedent
- any argument of the form: If A then B, Not A, thus Not B
- asserting that contrary or contradictory statements are both true
Errors in deductive reasoning. Improve use of major and minor premises when trying to make a conclusion.
Fallacy of Four Terms
- a syllogism has four terms
- two separate categories are said to be connected because they share a common property
- the predicate of the conclusion talks about all of something, but the premises only mention some cases of the term in the predicate
- the subject of the conclusion talks about all of something, but the premises only mention some cases of the term in the subject
Fallacy of Exclusive Premises
- a syllogism has two negative premises
Fallacy of Drawing an Affirmative Conclusion From a Negative Premise
- as the name implies
- a particular conclusion is drawn from universal premises
Fallacies of Explanation
These are clearly subjective and dubious methods of making claims.
- The phenomenon being explained doesn't exist
- Evidence for the phenomenon being explained is biased
- The theory which explains cannot be tested
- The theory which explains can only explain one thing
- The theory which explains does not appeal to underlying causes
Fallacies of Definition
Using improper technique or evidence in justifying a claim.
- The definition includes items which should not be included
- The definition does not include all the items which should be included
Failure to Elucidate
- The definition is more difficult to understand than the word or concept being defined
- The definition includes the term being defined as a part of the definition
- The definition is self-contradictory
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