max_i_m ([info]max_i_m) wrote,
@ 2009-06-01 21:25:00
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It depends on what the meaning of the word 'is' is.
“made from potato flour in the sense that one cannot say that it is not made from potato flour"

The Lord Justice Hath Ruled: Pringles Are Potato Chips.

As a mainstream mathematician, I'm pleased to see a court ruling utilizing proof by contradiction. The article goes on to state:


"The Supreme Court of Judicature had little patience with Procter & Gamble’s lawyerly attempts to break out of the potato chip category. The company argued that to be “made of potato” Pringles would have to be all potato, or nearly so. If so, Lord Justice Jacob noted, “a marmalade made using both oranges and grapefruit would be made of neither — a nonsense conclusion.”

He was even more dismissive of Procter & Gamble’s argument that to be taxable a product must contain enough potato to have the quality of “potatoness.” This “Aristotelian question” of whether a product has the “essence of potato,” he insisted, simply cannot be answered."



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[info]poslushnik
2009-06-02 02:36 am UTC (link)
> As a mainstream mathematician, I'm pleased to see a court ruling utilizing proof by contradiction.

Is there some weird sect of mathematicians who do not believe in proofs by contradiction?

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[info]max_i_m
2009-06-02 02:45 am UTC (link)
http://en.wikipedia.org/wiki/Double_negative_elimination

Double negative elimination is a theorem of classical logic, but not intuitionistic logic. Because of the constructive flavor of intuitionistic logic, a statement such as "It's not the case that it's not raining" is weaker than "It's raining". The latter requires a proof of rain, whereas the former merely requires a proof that rain would not be contradictory. (This distinction also arises in natural language in the form of litotes.)

See also

http://en.wikipedia.org/wiki/Intuitionistic_logic

Disclamer: I know nothing about logic, classical or otherwise (well, ok I read Logic as Algebra at some point).

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[info]poslushnik
2009-06-02 02:51 am UTC (link)
Ah, I've heard about something like that, except under some other name.

I'm curious how careful they are not to use proof by contradiction while proving things :)

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