Amphiboly is the fallacy of ambiguous construction. It occurs whenever the whole meaning of a statement can be taken in more than one way, and is usually the fault of careless grammar.
The Duchess has a fine ship, but she has barnacles on her bottom.
(This is a duchess who requires especially careful handling.)
The fallacy is capable of infinite variation. Many excellent examples of amphiboly make use of the confused pronoun: does the ‘she’ refer to the ship or to the Duchess? Similar confusion may occur with animals.
I met the ambassador riding his horse. He was snorting and steaming, so I gave him a lump of sugar.
(Would that all diplomats were so cheaply entertained.)
Misuse of the word ‘which’, or its omission for brevity, both produce many classic examples. (‘On the claim form I have filled in details about the injury to my spine which I now enclose.’) There are innumerable versions of the advertisement:
FOR SALE: Car by elderly lady with new body and spare tyre.
The mistake usually consists in the failure to appreciate that an alternative reading is possible. Sometimes the punctuation is misplaced; sometimes there is not enough of it to eliminate the ambiguity. Press headlines, with their need for both punch and brevity, are favourite long grasses from which the occasional delightful amphiboly will bounce into view. Legendary World War II masterpieces include:
MACARTHUR FLIES BACK TO FRONT
(With more variations still if the second word is taken to be a noun.)
FRENCH PUSH BOTTLES UP GERMANS!
(Hand-to-hand combat, yes. But this is ridiculous.)
Use of the amphiboly with intent to deceive is a favourite resort of oracles and fortune-tellers. A timely amphiboly enables the prophet to hedge his bets, having it both ways. After the outcome one can always take refuge in the meaning which was fulfilled. Croesus asked the oracle what would happen if he attacked Persia. The reply ‘A mighty empire will be humbled’ was prophetic indeed. But it was his own.
To become a skilled perpetrator of amphibolies you must acquire a certain nonchalance toward punctuation, especially commas. You must learn to toss off lines such as ‘I heard cathedral bells tripping through the alleyways’, as if it mattered not a whit whether you or the bells were doing the tripping. You should acquire a vocabulary of nouns which can be verbs and a grammatical style which easily accommodates misplaced pronouns and confusions over subject and predicate. The astrology columns in popular newspapers provide excellent source material.
The above article is from the book How To Win Every Argument by Madsen Pirie. The article is only for educational and informative purposes to explain and understand formal logic and logical fallacies. It is a great book, definitely worth a read!