# [FOM] Godel's Theorems

Kalin, Martin Kalin at cti.depaul.edu
Thu May 1 18:12:27 EDT 2003

```I think W. views *) as an instance of a more
general problem, the "conceptual confusion" that he
thinks permeates fom. He takes a hard line on
what math is:

"Mathematics consists entirely of calculations.
In mathematics, everything is algorithm and nothing is meaning (Bedeutung),
even when it doesn't look like that because we  seem to be using words to talk
about mathematical things. Even these words are used to construct an
algorithm."

For W., math deals with calculations (he's close to Kronecker here)
and "physics" (natural science broadly understood) deals with
semantics, in particular with the truth-value of propositions.

Marty Kalin
Professor, CTI
DePaul University
243 S. Wabash
Chicago, IL 60604
http://condor.depaul.edu/~mkalin

-----Original Message-----
From: Robbie Lindauer [mailto:robblin at thetip.org]
Sent: Thursday, May 01, 2003 4:31 PM
To: tbays at nd.edu
Cc: fom
Subject: Re: [FOM] Godel's Theorems

I think the Wittgenstein objection to *) is not that it isn't provable
or that it's not a mathematical statement, just that the word "proves"
here has been given a new meaning ("diagonalization") and that if you
allow that you can change the kinds of things that you call proof, then
you can prove anything.

As LW says, his point is not to disprove any particular mathematical
proposition, only to invite people to realize that the mathematical
paradise isn't what we think it is.

When a mathematician says "prove" s/he means that "if you use these
axioms and transformation rules, you 'get' these results".

LW would add a caveat (I think):

"There is no clarification for the word 'get' here.  We can decide to
play be the rules the way it is usually done but that doesn't get us
what was desired out of 'prove'."

Best,

robbie lindauer

>> *) there is a true sentence in the language of PA which is not
>> provable in PA.
>>
>> 1. Conventional wisdom is that this is now a fully established
>> theorem of mathematics (or ordinary mathematics as currently
>> practiced by the overwhelming majority of mathematicians). Is there
>> agreement on this?
>>
>> 2. For those who do not agree, do they believe that *) is not a
>> mathematical statement capable of mathematical proof? E.g., this
>> could be on the grounds that they do not accept the usual
>> mathematical definition of "true sentence in the language of PA".

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