Re: Is It True What They Say About Tarski?

Christian Whitaker (
Fri, 22 May 1998 19:04:51 PDT

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>Date: Fri, 22 May 1998 15:58:11 -0400 (EDT)
>From: Daniel Fabulich <>
>Subject: Re: Is It True What They Say About Tarski?
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>On Fri, 22 May 1998, Christian Whitaker wrote:
>> If a
>> sighted man says "le ciel est bleu" to a colorblind man and a blind
>> one will disagree or consider it a difference of opinion, and the
>> one will have to accept it as hearsay.

On Friday May 22 Daniel Fabulich wrote
>True, but if "blue" is strictly defined (which is the sort of thing you
>can do when you're talking about meta languages) then the sky TRULY is
>isn't blue. That it becomes black at night doesn't negate the proof;
>then, it truly is or isn't black.

I suppose one could solve the vagueness of blue by assigning it a strict
definition. Blue is light with a wavelength of 550 nm. Given such a
definition, the truth value of the statement 'le ciel est bleu' must be
no, as the value will be something other than precisely 550 nm, and will
fluctuate across the horizon and from second to second as light is
marginally refracted by water vapor and other chemicals inthe
atmosphere. The only way to get a true Trotskian statement on sky color
is to limit sky to a particular point in the sky to a particular point
in time and find the precise wavelength. In practice this will not be
very useful, because nobody says things like, 'le ciel est bleu at a
point 67 degrees and 35 minutes above and 23 degrees and 12 minutes to
the left of my reference point at exactly 3:57 PM.', even in a
I like Bart Kosko's notion that Trotskian statements should be
assigned a fuzzy truth value. An absolutely true statement is not
likely to be found outside of tautology (formal logic), so it is
sensible to assign 'le ciel est bleu' a .99 truth value on a clear day
at noon, and a .4 value in general, signifying that the sky is blue some
of the time (The sky is black would probably have a slightly higher
truth value, as the sky is black at night even if it is overcast,
although you might wish to factor in the presence of stars.) This
method also allows you to provide adjustments based on situation and
location, so you could assign that statement a .25 value within the
cloudy confines of Seattle. Some people dislike the lack of absolute
precision, but I think it preferable to the neurotic potential of the
endless search for "true" statements. Using this method, every
statement is true, although many are only true to a 0 degree.

-Christian Whitaker

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