Wednesday, May 9, 2012

Logical Fallacies

Fallacies of AMBIGUITY 

Definition:
incorrect reasoning through imprecise use of language 
An ambiguousword, phrase, or sentence is one that has two or more distinct meanings. The inferential relationship between the propositions included in a single argument will be sure to hold only if we are careful to employ exactly the same meaning in each of them. The fallacies of ambiguity all involve a confusion of two or more different senses.


Examples: 
she sees more of her children than her husband. 
- Really exciting novels are rare. But rare books are expesive. Therefore, really exciting novels are expensive.

Shakespeare used this more than once in his plays:

9. The Duke yet lives that Henry shall depose. (Henry VI, Part II; Act 1, Scene 4)
10. 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.
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 Last night I caught a prowler in my pyjamas.


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