Fallacy of Amphiboly

Ambiguity Fallacy Due to Grammar Defects

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Fallacy of Ambiguity

Explanation of the Fallacy of Amphiboly

The word amphiboly comes from the Greek ampho, which means "double" or "on both sides." This root, obviously enough, is closely related to the English world ambiguity.

Instead of using the same word with multiple meanings, as with the Fallacy of Equivocation, the Fallacy of Amphiboly involves the use of sentences which can be interpreted in multiple ways with equal justification due to some defect in the grammar, sentence structure, and punctuation or both.

Examples and Discussion of the Fallacy of Amphiboly

Often, the reason why this fallacy appears is due to poor or erroneous grammar, as with this example:

1. Last night I caught a prowler in my pajamas.

Was the person in pajamas when they caught the prowler or was the prowler trying to steal the pajamas? Strictly speaking, #1 isn't a fallacy because it isn't an argument; it only becomes a fallacy if someone tries to create an argument based it:

2. Last night I caught a prowler in my pyjamas. Therefore, it is important to keep your pyjamas locked up securely where no one else can get them.

The fallacy becomes more obvious when absurd conclusions are derived from the ambiguity. Usually, these errors aren't found in actual arguments. Instead, they are found in propositions or statements:

3. The anthropologists went to a remote area and took photographs of some native women, but they weren't developed. (from Marilyn vos Savant)

It is unclear whether or not the modifying phrase "were not developed" refers to the photographs or the women.

You're more likely to encounter this being used deliberately for humorous effect, for example in these alleged "Church Bulletin Blunders" from an email which periodically gets sent around:

4. Don't let worry kill you off - let the Church help.

5. Eight new choir robes are currently needed, due to the addition of several new members and to the deterioration of some older ones.

6. For those of you who have children and don't know it, we have a nursery downstairs.

7. Barbara remains in the hospital and needs blood donors for more transfusions. She is also having trouble sleeping and requests tapes of Pastor Jack's sermons.​

Amphiboly and Arguments

There aren't many instances where someone would deliberately introduce such ambiguity in their arguments. This can occur, though, when someone else's ambiguous statement is misinterpreted, and the arguer proceeds to draw incorrect conclusions based on that misinterpretation.

What causes such a misinterpretation to become a Fallacy of Amphiboly is that the ambiguity arises out of some grammatical or punctuation issue rather than vague terminology.

8. John told Henry that he had made a mistake. It follows that John has at least the courage to admit his own mistakes. (from Hurley)

Such misinterpretations may sound too obvious to take seriously, but they are taken seriously when the consequences are serious — like for example contracts and wills. If such documents have any grammar or punctuation issues which lead to an interpretation that benefits someone, it's a good bet that they will pursue it.

The most common case of this, however, is when it is used so that different audiences can get out of it whatever they are looking for - a tactic not unusual in politics:

9. I am opposed to taxes which slow economic growth.

What exactly is this political candidate trying to say?

Is she opposed to all taxes because they will slow economic growth? Or is she instead only to those taxes that have the effect of slowing economic growth? Some people will see one, and some will see the other, depending on their prejudices and agendas. Thus, we have a case of amphiboly here.

Amphiboly and Oracles

One other place where amphiboly appears is with oracles and psychic predictions. Oracles or oracular figures are notorious for giving ambiguous predictions which can be interpreted after events to have been true. The more vague and ambiguous a prediction is, the more likely it will be to come true, thus validating the power of the psychic or oracle.

Shakespeare used this more than once in his plays:

10. The Duke yet lives that Henry shall depose. (Henry VI, Part II; Act 1, Scene 4)

11. Be bloody, bold, and resolute; laugh to scorn the power of man, for none of woman born shall harm Macbeth. (Macbeth; Act 4, Scene 1)

Both of these predictions are ambiguous. In the first, it is unclear if there lives a duke whom Henry shall depose, or if there lives a duke who shall depose Henry. This ambiguity is caused by unclear grammar. The second example is the result of ambiguous terminology: Macbeth's enemy Macduff had been born by Caesarian section - "ripped untimely from his mother's womb" - and thus was not "of woman born" in the normal sense.

Such confusion is not limited to fiction: a common example of this ambiguity comes from Herodotus' writings about King Croesus of Lydia. Croesus feared the growing power of the Persian empire and asked many oracles what he should do and if he should march against King Cyrus. The Oracle of Delphi is reported to have answered:

11. ...that if he led an army against the Persians, he would destroy a great empire.

Considering this to be nice news, Croesus lead his armies into battle. He lost. If you look closely at the prediction, you'll notice that it is not clear which empire would be destroyed. Herodotus remarks that if Croesus had been smart, he would have sent back a question asking which empire the oracle meant.

When given an ambiguous prediction, people tend to believe whichever interpretation is most favorable to what they want anyway. Pessimistic people will believe the most pessimistic meaning, while optimistic people will believe the most favorable meaning.