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UGC NET PAPER 1 · UNIT 06 · MODULE 2: WESTERN LOGIC: ARGUMENT FORMS, FALLACIES AND LANGUAGE · TOPIC 5

Fallacies

Formal versus informal fallacies, then the three informal families with their Latin names and examples: relevance, presumption and ambiguity.

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  • Topic 5 of 19

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  1. 5.1What a Fallacy Is: Formal and InformalA fallacy is an error in reasoning that makes an argument unsound or invalid.
    • fallacy
    • Formal fallacies
    • form (structure)
    • Informal fallacies
    • content, language or context
  2. 5.2Fallacies of relevance (premises are irrelevant to the conclusion)Fallacy Latin name Meaning Example Appeal to force Argumentum ad baculum Threat is used in place of proof Accept my view or lose your job Appeal to pity Ad misericordiam…
  3. 5.3Fallacies of presumption (assume something unproved)Covers Complex (loaded) question, False cause ( non causa pro causa ), Accident, Converse accident (hasty generalisation), False dilemma and more.
    • Complex (loaded) question
    • post hoc ergo propter hoc
    • Accident
    • False dilemma
    • Slippery slope
  4. 5.4Fallacies of ambiguity (language is used in shifting senses)Fallacy Cause Equivocation A word is used in two different senses in the same argument Amphiboly Ambiguity from loose or faulty grammar and sentence construction Accent…
    • Equivocation
    • Amphiboly
    • Accent
    • Composition
    • Division

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5.1What a Fallacy Is: Formal and Informal#

In brief

A fallacy is an error in reasoning that makes an argument unsound or invalid.

  • fallacy
  • Formal fallacies
  • form (structure)
  • Informal fallacies
  • content, language or context

A fallacy is an error in reasoning that makes an argument unsound or invalid. Two broad classes exist.

  • Formal fallacies arise from the form (structure) of the argument and can be detected without knowing the subject matter. Examples: undistributed middle, illicit major, illicit minor, exclusive premises, four terms, affirming the consequent, denying the antecedent, existential fallacy.

  • Informal fallacies arise from the content, language or context of the argument. They are grouped as fallacies of relevance, ambiguity and presumption.

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5.2Fallacies of relevance (premises are irrelevant to the conclusion)#

In brief

Fallacy Latin name Meaning Example Appeal to force Argumentum ad baculum Threat is used in place of proof Accept my view or lose your job Appeal to pity Ad misericordiam…

Fallacy Latin name Meaning Example
Appeal to force Argumentum ad baculum Threat is used in place of proof Accept my view or lose your job
Appeal to pity Ad misericordiam Sympathy replaces evidence Pass me, I will lose my scholarship
Appeal to the people Ad populum Popularity or crowd emotion is used Everyone believes it, so it is true
Argument against the person Ad hominem Attacks the speaker, not the argument (abusive, circumstantial, tu quoque) He is a liar, so his theory is wrong
Appeal to improper authority Ad verecundiam Cites an authority outside their field A film star's view on nuclear physics
Appeal to ignorance Ad ignorantiam Claims truth because falsity is unproved (or vice versa) No one has disproved ghosts, so they exist
Irrelevant conclusion Ignoratio elenchi Proves something other than the point at issue Argues about crime to justify a tax
Red herring Diverts attention with an irrelevant issue
Straw man Misrepresents the opponent's view so it can be easily refuted
Tu quoque "You do it too" (a form of ad hominem circumstantial)
Genetic fallacy Judges a claim by its origin It came from a politician, so it is false

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5.3Fallacies of presumption (assume something unproved)#

In brief

Covers Complex (loaded) question, False cause ( non causa pro causa ), Accident, Converse accident (hasty generalisation), False dilemma and more.

  • Complex (loaded) question
  • post hoc ergo propter hoc
  • Accident
  • False dilemma
  • Slippery slope

  • Begging the question (petitio principii): the conclusion is assumed in the premises; circular reasoning.

  • Complex (loaded) question: a question presupposing a point not yet granted ("Have you stopped cheating?").

  • False cause (non causa pro causa): treating a non-cause as a cause. Its best-known type is post hoc ergo propter hoc (after this, therefore because of this).

  • Accident: applying a general rule to a special case where it does not apply.

  • Converse accident (hasty generalisation): moving from an exceptional or unrepresentative case to a general rule.

  • False dilemma: presenting only two alternatives when more exist.

  • Slippery slope: claiming one step will inevitably lead to a chain of bad consequences.

  • Naturalistic fallacy (G. E. Moore): deriving "good" from a natural property such as "pleasant" or "natural".

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5.4Fallacies of ambiguity (language is used in shifting senses)#

In brief

Fallacy Cause Equivocation A word is used in two different senses in the same argument Amphiboly Ambiguity from loose or faulty grammar and sentence construction Accent…

  • Equivocation
  • Amphiboly
  • Accent
  • Composition
  • Division
  • Trap
Fallacy Cause
Equivocation A word is used in two different senses in the same argument
Amphiboly Ambiguity from loose or faulty grammar and sentence construction
Accent Shifting emphasis or stress changes the meaning
Composition What is true of the parts is inferred to be true of the whole
Division What is true of the whole is inferred to be true of each part

Trap: composition and division are opposites. "Each brick is light, so the wall is light" is composition. "The team is excellent, so each player is excellent" is division.

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Test yourself on Fallacies

Practise with free MCQs and answer keys, then return here to fix what you got wrong.

↑ Module 2: Western Logic: Argument Forms, Fallacies and Language · All 19 topics in Logical Reasoning · Unit overview and sample MCQs

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