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Logic and rhetoric

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Marriage is a fine institution, but I'm not ready for an institution.
—Mae West, The 2,548 Best Things Anybody Ever Said

Equivocation (or doublespeak) is a logical fallacy that relies on the different meanings a word can have in different contexts.

It is a favorite fallacy of creationist and woo hucksters alike. It can be used both to seemingly belittle a concept or idea, or to raise one up to false pretenses. It can be used to disguise bullshit like in quantum woo where people like Deepak Chopra use equivocation to make their ideas sound like they have some basis in reality.

Equivocation is an informal fallacy and a fallacy of ambiguity, although its parent fallacy, the four-term fallacy, is a formal fallacy.


[edit] Form

P1: X is Y (meaning 1).
P2: Y (meaning 2) is Z.
C1: X is Z.

With letters representing words, this may seem obviously false, but when words are introduced, the fallacy becomes much less apparent.

[edit] Examples

[edit] Obviously false

P1: Noisy children are real headaches.
P2: An aspirin makes real headaches go away.
C1: An aspirin will make noisy children go away.

P1: Nothing is better than eternal happiness.
P2: A ham sandwich is better than nothing.
C1: A ham sandwich is better than eternal happiness.

P1: All bark is grown on trees.
P2: All dogs bark.
C1: All dogs are trees.

P1: 1 is a number.
P2: 2 is a number.
C1: 1 is 2.

In this case, the word "is" in the two premises is used differently in meaning than "is equivalent to" in the conclusion

[edit] Less obvious

  • "You have faith in science, and I have faith in God."
    This exploits the fact that "faith" is often used to mean "confidence," that is having a solid reason to be confident of something due to its past performance—this argument is an effort to equate science with religion, when in reality science does not require faith (meaning belief without evidence).

[edit] See also

[edit] External links

[edit] Footnotes

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