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  • False Conversion
  • False Dilemma
  • False Effect
  • Far-Fetched Hypothesis
  • Faulty Comparison
  • Gambler’s Fallacy
  • Genetic Fallacy
  • Hasty Generalization
  • Having Your Cake
  • Hedging
  • Historian’s Fallacy
  • Homunculus Fallacy
  • Hypnotic Bait and Switch
  • Hypothesis Contrary to Fact
  • The Fallacies: If–Mu
  • If-By-Whiskey
  • Illicit Contraposition
  • Illicit Major
  • Illicit Minor
  • Illicit Substitution of Identicals
  • Inconsistency
  • Inflation of Conflict
  • Jumping to Conclusions
  • Just Because Fallacy*
  • Just In Case Fallacy
  • Least Plausible Hypothesis
  • Limited Depth
  • Limited Scope
  • Logic Chopping
  • Ludic Fallacy
  • Lying with Statistics
  • Magical Thinking
  • Meaningless Question
  • Misleading Vividness
  • Missing Data Fallacy*
  • Modal (Scope) Fallacy
  • Moralistic Fallacy
  • Moving the Goalposts
  • Multiple Comparisons Fallacy
  • The Fallacies: Na–Ri
  • Naturalistic Fallacy
  • Negating Antecedent and Consequent
  • Negative Conclusion from Affirmative Premises
  • Nirvana Fallacy
  • No True Scotsman
  • Non Sequitur
  • Notable Effort
  • Overwhelming Exception
  • Package-Deal Fallacy
  • Poisoning the Well
  • Political Correctness Fallacy
  • Post-Designation
  • Prejudicial Language
  • Proof by Intimidation
  • Proving Non-Existence
  • Quantifier-Shift Fallacy
  • Quantum Physics Fallacy*
  • Questionable Cause
  • Rationalization
  • Red Herring
  • Reductio ad Absurdum
  • Reductio ad Hitlerum
  • Regression Fallacy
  • Reification
  • Relative Privation
  • Retrogressive Causation
  • Rights To Ought Fallacy*
  • The Fallacies: Sc–Wi
  • Scapegoating
  • Selective Attention
  • Self-Sealing Argument
  • Shoehorning
  • Slippery Slope
  • Special Pleading
  • Spiritual Fallacy*
  • Spotlight Fallacy
  • Statement of Conversion
  • Stereotyping
  • Stolen Concept Fallacy
  • Strawman Fallacy
  • Style Over Substance
  • Subjectivist Fallacy
  • Subverted Support
  • Sunk-Cost Fallacy
  • Suppressed Correlative
  • Texas Sharpshooter Fallacy
  • Tokenism
  • Two Wrongs Make a Right
  • Unfalsifiability
  • Unwarranted Contrast
  • Use-Mention Error
  • Weak Analogy
  • Willed Ignorance
  • Wishful Thinking
  • Affirmative Conclusion from a Negative Premise

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    (also known as: illicit negative, drawing a negative conclusion from affirmative premises, fallacy of negative premises)

    This is our first fallacy in formal logic out of about a dozen presented in this book.  Formal fallacies can be confusing and complex, and are not as common in everyday situations, so please don’t feel lost when reading through the formal fallacies—do your best to understand them as I do my best to make them understandable.

    New Terminology:

    Syllogism: an argument typically consisting of three parts: a major premise, a minor premise, and a conclusion.

    Categorical Term: usually expressed grammatically as a noun or noun phrase, each categorical term designates a class of things.

    Categorical Proposition: joins together exactly two categorical terms and asserts that some relationship holds between the classes they designate.

    Categorical Syllogism: an argument consisting of exactly three categorical propositions: a major premise, a minor premise, and a conclusion, in which there appear a total of exactly three categorical terms, each of which is used exactly twice.

    Description: The conclusion of a standard form categorical syllogism is affirmative, but at least one of the premises is negative. Any valid forms of categorical syllogisms that assert a negative premise must have a negative conclusion.

    Logical Form:

    Any form of categorical syllogism with an affirmative conclusion and at least one negative premise.

    Example #1:

    No people under the age of 66 are senior citizens.

    No senior citizens are children.

    Therefore, all people under the age of 66 are children.

    Explanation: In this case, the conclusion is obviously counterfactual although both premises are true.  Why?  Because this is a categorical syllogism where we have one or more negative premises (i.e., “no people...” and “no senior citizens...”), and we are attempting to draw a positive (affirmative) conclusion (i.e., “all people...”). 

    Example #2:

    No donkeys are fish.

    Some asses are donkeys.

    Therefore, some asses are fish.

    Explanation: This is a categorical syllogism where we have a single negative premise (i.e., “no donkeys”), and we are attempting to draw a positive (affirmative) conclusion (i.e., “some asses”).

    Exception: None.

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