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What Gödel Discovered

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161–170 of 271 posts

Re: What Gödel Discovered

#161
Contrary to popular opinion, [Gödel 1931] did not actually prove inferential undecidability (sometimes called "inferential incompleteness") of Russell's Principia Mathematica for the reasons explained here:

https://papers.ssrn.com/abstract=3603021

The article linked above gives a correct proof of inferential incompleteness.

Re: What Gödel Discovered

#162
post #9

Cf. Douglas Hofstadter's Metamagical Themas : > In March of 1977, I met the great AI pioneer Marvin Minsky for the first time. It was an unforgettable experience. One of the most memorable remarks he made to me was this one: "Gödel should just have thought up Lisp; it would have made the proof of his theorem much easier." I knew exactly what Minsky meant by that, I could see a grain of truth in it, and moreover I kne…

I can't decide whether Gödel's method and Lisp are yet another Strange Loop [1]. Fortunately, I am still in the beginning.

[1] https://www.goodreads.com/book/show/123471.I_Am_a_Strange_Lo...

Re: What Gödel Discovered

#163
post #124

Lispers learned marketing, bravo! The only issue is the missing credit to the Quanta article https://www.quantamagazine.org/how-godels-incompleteness-the... .

That's pretty rude of you. I didn't read that essay, but I did reference about 4 essays / books that I did read :). Went through the quanta article -- it seems reasonably different (doesn't go deep on how proof, subst, work, etc) -- I suspect the similarities stem from both of us reading Nagel and Newman's book.

Ok, then I apologize, it seemed very similar and recent.

Re: What Gödel Discovered

#164

Earlier quoted context omitted.

"I will just mention my main two quibbles" -- Poking through your history, why do you quibble on the word truth so often? Do we not agree there are statements that are true? Do we not agree there are provable true statements ? If there are unprovable statements in any consistent set of axioms, might we also conclude there also be an unprovable but true statements?

It's because it's a huge can of worms that leads to really grandiose claims that aren't supported by Godel's statements, of the sort the article is already beginning to make. It also shifts the conversation into becoming fundamentally a philosophical question rather than a logical or mathematical one, which is okay, but considerably changes the table stakes of what background knowledge we need. > If there are unprova…

dwohnitmok, I think you make a good point about Completeness missing out on the action in OP's post, which is nevertheless a good post and better than popular treatments. In fact, I remember thinking in class, "What, there is Completeness theorems as well as Incompleteness?" This is due to a similar phenomenon as we see with quantum mechanics in popular writing, where mostly the sensational, which aren't really sensational, is written.

In any case, my contribution here is something else: The most interesting part of the natural numbers object and its role in incomplete logical systems is to me the more humble notion of... unique prime factorisation.

If that had failed, so too would the Godel numbering system. I am not a number theorist, but this to me would be an interesting spin off from OP's post. The divisibility lattice is a good starting point, but apart from such basic constructions, the actual proof of unique prime factorisation to me is more historic than informative, and steps such as Bezout's Identity are just as "mythical" to me as Godel's Incompleteness Theorem, if we are using bad word choices. Conversely, numbers are just permutations on prime generators, but crucially, usually we start with addition before we start with multiplication.

Re: What Gödel Discovered

#165

Earlier quoted context omitted.

This brought a big smile to read, thank you :)

There is an extraordinarily minor typo: “PM-LIsp” I point it out only because your work here is so good that it feels wrong not to smooth out any small splinters. Thank you for making this!

[deleted]

Re: What Gödel Discovered

#166

Earlier quoted context omitted.

There is an extraordinarily minor typo: “PM-LIsp” I point it out only because your work here is so good that it feels wrong not to smooth out any small splinters. Thank you for making this!

Oi, thanks for the kind words and the catch! Updated (should take a few minutes to show up)

I think I maybe noticed another typo... The last two axioms don't have matching parentheses? It looks like one more is opened than closed if I counted right.

Re: What Gödel Discovered

#167

Earlier quoted context omitted.

> often by exaggerating their consequences. So you assert, many think differently. Edit: To clarify, are you asserting that they do /not/ extend into philosophy? What exaggerations are you specifically referring to?

Godel's theorems have philosophical ramifications, but then again so do basically all theorems given the right framing. It is nonetheless true that Godel's theorems are a particular focal point of discussion around mathematical philosophy (but again one which has surprisingly few ramifications for mathematics as a whole) and a very fruitful one at that. I'm not dismissing the idea of having a philosophical discussion…

Thank you for your clarity. This discussion chain may have kicked of an existential crisis. I think you might have exposed me to a Lovecraftian horror. The article and your discussion have been, if not mind altering, very much mind expanding.

I can't say I've followed all of the nuance in your (argument?) comments. I do know I'm going to be chewing on this for a while. I've come to grips with horror of saccades, fascinating to learn about new ways my mind, uh, decides what is true.

In any case, I appreciate your long thoughtful responses. May not mean much to you, but for at least one reader, it means a lot to me.

Re: What Gödel Discovered

#168
post #135

Very interesting. I'm wondering if this has implications in physics ? Since "the book of nature is written in mathematical language", does this mean that attempts to find a unified theory of everything are doomed ? I'm thinking not necessarily, since we wouldn't need to prove all possible physical phenomena, only those that actually happen, but how do we know if they are among the one that can be proven ?

The implications are really on the concept of language. It proves that there is no language that can be complete; as such, we cannot express a complete system, even if it existed. So a unified theory of everything might well exist, but you wouldn’t be able to describe it. Which is a nice philosophical riddle.

Re: What Gödel Discovered

#170

This article spectacularly misses a big chunk of the point of Lisp, by applying Gödel-numbering to the printed representation of the syntax, rather than to the object that it denotes.

This is exactly what came to my mind as I was reading this article. Would it make a difference if it was applied to syntax objects?
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