Stephen Downes Guide to the Logical Fallacies

        Copyright Stephen Downes, 1995-2000


Taken from

  1. Fallacies of Distraction

  2. Appeals to Motives in Place of Support

  3. Changing the Subject

  4. Inductive Fallacies

  5. Fallacies Involving Statistical Syllogisms

  6. Causal Fallacies

  7. Missing the Point

  8. Fallacies of Ambiguity

  9. Category Errors

  10. Non Sequitur

  11. Syllogistic Errors

  12. Fallacies of Explanation

  13. Fallacies of Definition


Fallacies of Distraction


      False Dilemma: two choices are given when in fact there are three options

      From Ignorance: because something is not known to be true, it is assumed to be false

      Slippery Slope: a series of increasingly unacceptable consequences is drawn

      Complex Question: two unrelated points are conjoined as a single proposition


Appeals to Motives in Place of Support


      Appeal to Force: the reader is persuaded to agree by force

      Appeal to Pity: the reader is persuaded to agree by sympathy

      Consequences: the reader is warned of unacceptable consequences

      Prejudicial Language: value or moral goodness is attached to believing the author

      Popularity: a proposition is argued to be true because it is widely held to be true


Changing the Subject


      Attacking the Person:

1.      The person's character is attacked

2.      The person's circumstances are noted

3.      The person does not practice what is preached

      Appeal to Authority:

1.      The authority is not an expert in the field

2.      Experts in the field disagree

3.      The authority was joking, drunk, or in some other way not being serious

      Anonymous Authority: 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


Inductive Fallacies


      Hasty Generalization: the sample is too small to support an inductive generalization about a population

      Unrepresentative Sample: the sample is unrepresentative of the sample as a whole

      False Analogy: the two objects or events being compared are relevantly dissimilar

      Slothful Induction: the conclusion of a strong inductive argument is denied despite the evidence to the contrary

      Fallacy of Exclusion: evidence which would change the outcome of an inductive argument is excluded from consideration


Fallacies Involving Statistical Syllogisms


      Accident: a generalization is applied when circumstances suggest that there should be an exception

      Converse Accident : an exception is applied in circumstances where a generalization should apply


Causal Fallacies


      Post Hoc: because one thing follows another, it is held to cause the other

      Joint effect: one thing is held to cause another when in fact they are both the joint effects of an underlying cause

      Insignificant: one thing is held to cause another, and it does, but it is insignificant compared to other causes of the effect

      Wrong Direction: the direction between cause and effect is reversed

      Complex Cause: the cause identified is only a part of the entire cause of the effect


Missing the Point


      Begging the Question: the truth of the conclusion is assumed by the premises

      Irrelevant Conclusion: an argument in defense of one conclusion instead proves a different conclusion

      Straw Man: the author attacks an argument different from (and weaker than) the opposition's best argument


Fallacies of Ambiguity


      Equivocation: the same term is used with two different meanings

      Amphiboly: the structure of a sentence allows two different interpretations

      Accent: the emphasis on a word or phrase suggests a meaning contrary to what the sentence actually says


Category Errors


      Composition: because the attributes of the parts of a whole have a certain property, it is argued that the whole has that property

      Division: because the whole has a certain property, it is argued that the parts have that property


Non Sequitur


      Affirming the Consequent: any argument of the form: If A then B, B, therefore A

      Denying the Antecedent: any argument of the form: If A then B, Not A, thus Not B

      Inconsistency: asserting that contrary or contradictory statements are both true


Syllogistic Errors


      Fallacy of Four Terms: a syllogism has four terms

      Undistributed Middle: two separate categories are said to be connected because they share a common property

      Illicit Major: the predicate of the conclusion talks about all of something, but the premises only mention some cases of the term in the predicate

      Illicit Minor: 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 

      Existential Fallacy: a particular conclusion is drawn from universal premises


Fallacies of Explanation


      Subverted Support: The phenomenon being explained doesn't exist

      Non-support: Evidence for the phenomenon being explained is biased

      Untestability The theory which explains cannot be tested

      Limited Scope The theory which explains can only explain one thing

      Limited Depth The theory which explains does not appeal to underlying causes


Fallacies of Definition


      Too Broad The definition includes items which should not be included

      Too Narrow 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

      Circular Definition The definition includes the term being defined as a part of the definition

      Conflicting Conditions The definition is self-contradictory



   For Educators

       Stephen Downes Guide to the Logical Fallacies

        Copyright Stephen Downes, 1995-2000


Taken from