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Science Forum Index » Logic Forum » What should I say to the post-grads about Godel?...
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| Nam D. Nguyen... |
 Posted: Thu Jun 19, 2008 10:22 pm |
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Marshall wrote:
Quote: On Jun 19, 6:15 am, "Nam D. Nguyen" <namducngu... at (no spam) shaw.ca> wrote:
Is the sky *still* "blue" to those who happen to have some kind
of vision disorder?
For instance, why are you so sure that they wouldn't see the sky as
"red"? In addition, what about aliens whose biological composition
is different than us: why would the sky *must necessarily* be "blue"
and not "purple" to them?
I anticipated these objections and headed them off when I said:
Of course you didn't head them off at all! In fact there were incorrect/
incoherent reasoning at critical points!
Quote:
The sky is blue. This is true independent of your subjective
experience of what blue looks like. If you were color blind, heck
even if you were born without eyes, you could still learn that
"color" is a thing that describes a particular visual quality, that
there are colors named "red" and "blue", and that the sky is blue.
How do the born-without-eyes go from there being colors named "red" and
"blue" to conclude that "the sky is blue"? What would prevent them from
concluding "the sky is red" thereby further concluding that "the sky is NOT blue"?
Even if you teach them to *associate* the word "blue" to a fixed frequency f
of light polarized by air molecules, why could they *not subjectively*
associate that frequency f with another word, like "red"?
So you see; you tried but didn't successfully head off my objection that
the knowledge of the blueness of the sky must be subjective!
Quote:
The sky must necessarily be blue to hypothetical aliens because
that is the name for the range of wavelengths of light that are
preferentially admitted by the atmosphere. Which wavelengths
those are don't change when aliens visit.
Besides the *choice* (which is *subjective*) to label a light frequency
with any *arbitrary* name ("red", "green", "blue",...), the light frequencies
themselves are *not of an objective physical property*! The Doppler Effect
will guarantee that we'll never see a fixed frequency for the sky, unless
all the atoms and photons are "frozen" and motionless at 0 Kelvin degree,
which is an impossibility!
So again, you've failed to dispel the notion that the truth and the knowledge
of the sentence "the sky is blue" is subjective. And you've failed to demonstrate
that knowledge, in general, is *not* objective.
Sometimes it's much easier to acknowledge a truth than to deny it, I'd suggest
to you!
Quote:
I am of course using inductive reasoning to conclude this; not
actual experimental results.
Or *am* I?<spooky music
Marshall
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