🚀 go-pugleaf

In article <1992Oct30.172420.1@eagle.wesleyan.edu> skumar@eagle.wesleyan.edu
writes:
>Please correct me if I am wrong but I think that if I found a creature which
>was like a crow in all respects but it was white in color, I would call it an
>albino crow or something. I would not call it just "a crow". Does this not
mean
>that we accept "all crows are black" by definition so we need not prove it?
>
>just wondering....
>
>wonko, the sane

I put this idea to the test of experiment by asking my secretary (who is Irish)
what colour crows are in Ireland (where, as I mentioned before, crows are
"hooded" - half grey). She answered "black, kind of grey", but said nothing
about them not being proper crows.

Not that this is terribly interesting from a philosophical (or sci.logic) point
of view, but I think the discussion was becoming a bit speculative.

Steve Vickers.

In article <1992Oct30.172420.1@eagle.wesleyan.edu> skumar@eagle.wesleyan.edu writes:
>Please correct me if I am wrong but I think that if I found a creature which
>was like a crow in all respects but it was white in color, I would call it an
>albino crow or something. I would not call it just "a crow". Does this not mean
>that we accept "all crows are black" by definition so we need not prove it?
>

In England, there are some piebald crows, that is crows that are
black and white. They have a special name. They are called magpies.
They have become more common in recent years, probably because they
were made a protected species.

I missed the start of this thread, but wonder if the the problem
that people are having with

All crows are not black

is along the lines of

All that glitters is not gold

where the "All" is, in fact, a peculiar idiom of the English language
that means "Some", but with an emphasis of a kind.

The book from which I have been learning logic, namely Teach Yourself
Logic, warns that All ... not ... of this kind needs to be expressed as

No ... ...

in order to avoid this idiom.

Thus, All crows are not black, in the idiomatic form is really

Some crows are not black

Whilst, All crows are not black, in the literal sense of the words is really

No crows are black



I have found the study of Logic fascinating, but still have a long way
to go. I note that it was a compulsary subject in the Medieval Universities.
I believe that it should become a compulsary subject again, starting in
schools and continuing in everyday usage, much as other basic skills such
as reading, writing, spelling and mathematics.

----

Hubert was trying to do something but could not get the
duff equipment to work. Hubert asked for better equipment.
Hubert heard "A bad workman always blames his tools" said.
"Ah", responded Hubert quickly, "Your implied syllogism exhibits
the Fallacy of the Undistributed Middle".
"Now, may I please have some proper equipment?"

In article <Bx5DIB.8qF@cck.coventry.ac.uk>, esz001@cck.coventry.ac.uk
(Will Overington) writes:
|> I missed the start of this thread, but wonder if the the problem
|> that people are having with
|> 
|> All crows are not black
|> 
|> is along the lines of
|> 
|> All that glitters is not gold
|> 
|> where the "All" is, in fact, a peculiar idiom of the English language
|> that means "Some", but with an emphasis of a kind.
|> 
Robert Anton Wilson, in his various explications of the Non-Aristotelian
work of Korsybski, discusses in
some length the problems inherent in this statement; basically, it seems
to be the use of the verb 'to be',
which is usually incorrect. Elimination of the absolute assertion in its
pernicious forms copes with many
problems of semantics; the usual example list includes:
   the electron is a wave -> the electron, constrained thus, manifests
wave properties
   the electron is a particle -> the .... manifests particle properties
   Janet is a feminist -> Janet said she thinks women can program
computers as well as men
   A crow is black -> The crows I have seen were black
   that is a lie -> that seems like a lie to me.
Wilson comes up with a neat proposal; namely, the replacement of the
word 'all' in general usage by the word 'sombunall', being a contraction
of 'SOMe BUt Not ALL'; thus sombunall crows are black, which I think we
could all agree on?
Rich!
the above statements seem to me to be mine and no-one else's; I make no
absolute assertions in them, so don't blame me if you still confuse my
maps with your territory.
(sorry if this is obvious, but I thought it solved a few problems.)   

In article <Bx5DIB.8qF@cck.coventry.ac.uk> esz001@cck.coventry.ac.uk (Will Overington) writes:
>I missed the start of this thread, but wonder if the the problem
>that people are having with
>
>All crows are not black
>
>is along the lines of
>
>All that glitters is not gold
>
>where the "All" is, in fact, a peculiar idiom of the English language
>that means "Some", but with an emphasis of a kind.

This is an ambiguity of English (and many other languages), and
concerns the scope of adverbs.  The question here is whether the adverb
"not" governs the whole sentence: "Not(all that glisters is gold)" or
just the predicate: "All that glisters (not(is gold))".  More
precisely, "Not(for all x[glister(x) -> gold(x)])" vs. "For all
x[glister(x) -> not(gold(x))]".  (For some reason "For all
x[not(glister(x) -> gold(x))]" is not among the permitted readings, any
linguists out there care to explain this?)

>The book from which I have been learning logic, namely Teach Yourself
>Logic, warns that All ... not ... of this kind needs to be expressed as
>
>No ... ...
>
>in order to avoid this idiom.

Absolutely, to avoid the ambiguity.

>I have found the study of Logic fascinating, but still have a long way
>to go. I note that it was a compulsary subject in the Medieval Universities.
>I believe that it should become a compulsary subject again, starting in
>schools and continuing in everyday usage, much as other basic skills such
>as reading, writing, spelling and mathematics.

I have very mixed feelings about this.  Freshman math at Gunn High
(where my 14 year old goes) started out this year with a couple of
weeks of propositional logic before getting into geometry etc.  My
intuitive feeling was that she got much less useful math out of the
logic than out of the geometry.  On the other hand logic is fundamental
to thought, and even if humans don't reason propositionally it is good
to at least be aware of a logical system that they could plausibly
reason in, albeit clumsily.

Based on what I've observed in people's thought processes I'm pretty
convinced that human propositional logic is considerably weaker than
intuitionistic logic.  I think it would be more useful to teach these
weaker logics in high school, both because they entail fewer axioms and
because they are more representative of human thought.  However even
grad school curricula today barely touch on these "minimal logics", and
when they do they don't make the connections with human reasoning that
I am pretty certain are there to be made.
-- 
Vaughan Pratt				There's no truth in logic, son.

skumar@eagle.wesleyan.edu writes:

>Please correct me if I am wrong but I think that if I found a creature which
>was like a crow in all respects but it was white in color, I would call it an
>albino crow or something. I would not call it just "a crow". Does this not mean
>that we accept "all crows are black" by definition so we need not prove it?

Isn't this the "grue" problem? The "grue" problem came about (if I remember
correctly) because all emeralds were green and believed by reputable scientists
that they could only be green. Then they found blue ones...

-- 
===============================================================================
Steve (really "D. E.") Stevenson           steve@hubcap.clemson.edu
Department of Computer Science,            (803)656-5880.mabell
Clemson University, Clemson, SC 29634-1906

In article <1992Nov4.184630.3575@hubcap.clemson.edu> steve@hubcap.clemson.edu ("Steve" Stevenson) writes:
>skumar@eagle.wesleyan.edu writes:
>
>>Please correct me if I am wrong but I think that if I found a creature which
>>was like a crow in all respects but it was white in color, I would call it an
>>albino crow or something. I would not call it just "a crow". Does this not mean
>>that we accept "all crows are black" by definition so we need not prove it?
>
>Isn't this the "grue" problem? The "grue" problem came about (if I remember
>correctly) because all emeralds were green and believed by reputable scientists
>that they could only be green. Then they found blue ones...
>
>-- 
>===============================================================================
>Steve (really "D. E.") Stevenson           steve@hubcap.clemson.edu
>Department of Computer Science,            (803)656-5880.mabell
>Clemson University, Clemson, SC 29634-1906

`Grue' was an invented word by Nelson Goodman; something is grue if it is
green before 1 January 2000 and blue thereafter; therefore every confirmation
of the sentence `all Xs are green' is also a confirmation of the
sentence `all Xs are grue' (before 2000).

In article <1992Nov4.170813.27890@CSD-NewsHost.Stanford.EDU> 
pratt@Sunburn.Stanford.EDU (Vaughan R. Pratt) writes:
>I have very mixed feelings about this.  Freshman math at Gunn High
>(where my 14 year old goes) started out this year with a couple of
>weeks of propositional logic before getting into geometry etc.  My
>intuitive feeling was that she got much less useful math out of the
>logic than out of the geometry.  On the other hand logic is fundamental
>to thought, and even if humans don't reason propositionally it is good
>to at least be aware of a logical system that they could plausibly
>reason in, albeit clumsily.

My logic professor brought up the story of Bertrand Russell.  I think
(correct me if I'm wrong), that he and a co-author set out to prove that
all math was based on logic, and it took them two volumes to logically
prove that 1+1=2.


-- 
Keith K. Higa                         Lewis & Clark College    
higa@lclark.edu                       Portland, OR, USA
In a hierarchy each member tends to rise to his/her level of incompetence.
                                 --The Peter Principle

In article <1992Nov4.184630.3575@hubcap.clemson.edu> steve@hubcap.clemson.edu ("Steve" Stevenson) writes:

>Isn't this the "grue" problem? The "grue" problem came about (if I remember
>correctly) because all emeralds were green and believed by reputable scientists
>that they could only be green. Then they found blue ones...

Are you joking here?  Anyway, in case anyone hasn't heard about the grue
paradox, this isn't it!