Alias: Amphibology

Taxonomy: Logical Fallacy > Informal Fallacy > Ambiguity > Amphiboly

Subfallacy: Scope Fallacy


…[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.1



Linguistically, an amphiboly is a type of ambiguity that results from ambiguous grammar, as opposed to one that results from the ambiguity of words or phrases—that is, equivocation. Logically, the fallacy of amphiboly occurs when a bad argument trades upon grammatical ambiguity to create an illusion of cogency.

There are at least three distinct types of amphiboly:

  1. Misplaced modifiers:

    In the Marx brothers movie Animal Crackers, Groucho Marx's character Captain Spaulding has just returned from an African safari when he speaks the following lines:

    One morning I shot an elephant in my pajamas. How he got into my pajamas I'll never know.2

    Grammatically, the adjectival phrase "in my pajamas" ought to modify "an elephant", which it immediately follows. However, common sense suggests that it modifies "I". Then, the amphiboly is exploited for humor in the punch line.

  2. Ambiguous reference of pronouns:

    Captain Spaulding goes on in the same scene to speak the following lines:

    We took some pictures of the native girls, but they weren't developed. But we're going back again in a couple of weeks.2

    Which were undeveloped: the pictures or the native girls? The pronoun "they" is ambiguous between the two, though presumably intended to refer to the antecedent noun phrase "some pictures of the native girls", but its position leaves open the possibility that it refers to the phrase "native girls". The punch line then plays on this latter possibility.

  3. Ambiguity of scope:

    See the subfallacy Scope Fallacy, above, for an explanation of ambiguous scope.


Amphiboly is one of the thirteen fallacies identified by Aristotle in On Sophistical Refutations3, as well as one of the six that depend on language. The word "sophistical" in the title of the treatise refers to the sophists, who were teachers of rhetoric in Aristotle's time. According to Aristotle and his teacher Plato4, the sophists were often guilty of making ambiguous arguments, including amphibolous ones. Many of these arguments exploited types of ambiguity peculiar to the Greek language, so that they are almost impossible to translate into English, but here's the best that Aristotle gives: "I wish that you the enemy may capture." Who is wished to capture whom? Do I wish that you capture the enemy or that the enemy capture you?


Amphibolies are linguistic boobytraps which, as seen in the above examples, are frequently exploited for laughs. However, seldom do they occur in fallacious arguments. When they do, as in the kind of examples associated with the ancient sophists that Aristotle gives, the effect is primarily one of confusion rather than conviction. Unscrupulous debaters may use amphibolies to befuddle their opponents instead of convincing them.

Analysis of the Example:

This is an example of amphiboly as a phenomenon of language: specifically, an example of the first type of amphiboly discussed in the Exposition, above. It is ambiguous as to what part of the sentence the phrase "when in actual service in time of war or public danger" modifies, as is discussed in the example, itself. The amphiboly is not part of an argument, so a fortiori it is not part of a fallacious argument. However, it is a logical boobytrap since, as pointed out in the example, which way the sentence is interpreted could make a legal difference.


  1. Robert E. Rodes, Jr. & Howard Pospesel, Premises and Conclusions: Symbolic Logic for Legal Analysis (Prentice-Hall, 1997), p. 11.
  2. George S. Kaufman & Morrie Ryskind, Animal Crackers (1930).
  3. Aristotle, On Sophistical Refutations.
  4. See, in particular: "Euthydemus".