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Amphiboly

Alias: Amphibology

Type: Ambiguity

Example:

…[C]onsider the Fifth Amendment to the United States Constitution:
No person shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a grand jury, except in cases arising in the land or naval forces, or in the militia, when in actual service in time of war or public danger…

It is not clear whether the expression "when in actual service in time of war or public danger" attaches just to "in the militia" or to all of "in the land or naval forces, or in the militia". This unclarity makes a big difference, especially to someone "in the land or naval forces" who has been accused of committing a crime during peacetime.

Source: Robert E. Rodes, Jr. & Howard Pospesel, Premises and Conclusions: Symbolic Logic for Legal Analysis (Prentice-Hall, 1997), p. 11.

Exposition:

Linguistically, an amphiboly is an ambiguity which results from ambiguous grammar, as opposed to one that results from the ambiguity of words or phrases—that is, Equivocation. The fallacy of Amphiboly occurs when a bad argument trades upon grammatical ambiguity to create an illusion of cogency. Amphibolies are often linguistic boobytraps, but less frequently do they occur in fallacious arguments.

There are at least the following distinct types of amphiboly:

  • Ambiguous reference of pronouns

    Example

    The anthropologists went to a remote area and took photographs of some native women, but they weren't developed.

    Source: Marilyn vos Savant, The Power of Logical Thinking (St. Martin's Press, 1996), p. 76.

    In this example, the pronoun "they" is ambiguous between the photographs and the native women, though presumably it was intended to refer to the former.

  • Misplaced modifiers

    Example

    One morning I shot an elephant in my pajamas. How he got into my pajamas I'll never know.

    Source: Morrie Ryskind, spoken by Groucho Marx in the movie Animal Crackers.

    In the set-up of this joke, it's ambiguous whether the modifying phrase "in my pajamas" modifies "I" or "an elephant", though common sense suggests the former. Then, the amphiboly is exploited for humor in the punch line.

  • Ambiguity of scope
    See the subfallacy: Scope Fallacy

Funny Fallacy:

Helicopter powered by human flies

Source: Jay Leno (compiler), More Headlines: Real but Ridiculous Samplings from America's Newspapers (Warner Books, 1990), p. 56.

This headline has a misplaced modifier. Presumably, the headline writer meant: "Human-powered helicopter flies". Subfallacy: Scope Fallacy

Sources:

Acknowledgement: The road sign photograph comes from RoadTrip America's collection of funny signs.


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