I think I have figured out why
BurntSynapse has been saying such bizarre things about Gödel's theorems. Explaining and documenting my diagnosis will make this a long post, and my attempt to explain Gödel's theorems to him will make it even longer.
Until today, I did not understand why
BurntSynapse writes things like this:
The goal of my last question was understand how the words in your explanation (or any sentence) can provide meaning without establishing some context.
Quine and Duhem used the term "auxilliary hypotheses" for the contextual resources that provide meaning, without them meaning cannot exist.
When we say "rules of syntax", we know what it refers to - the words establish meaning by virtue of conceptual webs of belief about those words & concepts. Each of them has the same property.
It's fine to refer to a "context free something", but as soon as we say a "context free syntax" we've established it as not a "context free panda bear". As soon as we say "syntax", or "panda", we are establishing limits that are subject to definition, changes in definitions, (including radical changes) and any weakness we inherited from the evolution of the term, etc. This is stipulating some context, and necessary.
Your counter example is represented by meaningful statements. Meaningfullness is an entirely different attribute of statements than whether they are right, wrong, accurate, supported, fallacious, or whether anyone understands any of their meaning, especially me.
This is why I don't think the content of those statements matter to my claim about their reliance on auxiliary hypotheses.
I'm not the Sochi skier, I'm the coach.
What's going on here, I think, is that
BurntSynapse doesn't have the slightest idea of what the words "incompleteness" and "completeness" mean when we're talking about Gödel's incompleteness and completeness theorems. Those are technical terms, with precise mathematical meanings. When someone like
BurntSynapse tries to understand Gödel's theorems or their implications without realizing the words "completeness" and "incompleteness" mean something rather different from what English dictionaries say they mean, we're liable to hear the sort of thing
BurntSynapse said above.
My prior confessions of abject ignorance of advanced (and no doubt some basic) math bear repeating it seems. To all: I'm completely unqualified to understand, much less assess the validity of proofs for just about anything more complex than 5 or 6. I'm no mathematician - at all.
I'm glad you realize that, but I don't think you've thought it through. Because you are not a mathematician, you should listen when mathematicians warn you about your mistakes, and you should not continue to assert your own uninformed opinions after mathematicians have told you you're wrong.
Three days ago, I told you your reading of Gödel's incompleteness theorems is wrong:
My read of Gödel's incompleteness theorems, (first learned from Gödel, Escher, Bach and as described therein) is that the incompleteness he describes in dialog form is analogous to the project management principles of inherently incomplete documentation, and the issue that PM standards are limited in their ability to define when to apply any particular guideline.
That's a fairly bizarre misreading of Gödel's incompleteness theorems.
Apparently I didn't say that strongly enough. Let me try again: Your reading of Gödel's incompleteness theorems is spectacularly wrong, hopelessly incorrect. Your reading of Gödel's incompleteness theorems is so stupendously wrong that it's fair to say you know less about their implications for mathematics or physics than someone who's never even heard of those theorems.
For example:
Yes, that seems accurate as an illustration of where completeness for rules governing the application of rules can never be totally documented, it must be assumed.
No, no, a thousand times no. That is spectacularly wrong, hopelessly incorrect.
I corrected you by citing Gödel's completeness theorem as a counterexample. You didn't understand that counterexample, so I cited an entire class of mundane counterexamples I thought would be familiar to anyone who's ever heard of software project management. You then went off on a tangent that made no sense to me.
You, however, thought it made sense. That means you didn't pay attention when I told you your understanding of Gödel's incompleteness theorems is "fairly bizarre". Instead of listening to correction by domain experts, you continued to rely on your own incorrect understanding of the theorems.
If we assume you continued to believe the notion of incompleteness that Gödel proved in his incompleteness theorems "is analogous to the project management principles of inherently incomplete documentation, and the issue that PM standards are limited in their ability to define when to apply any particular guideline", then it becomes much easier to understand why you have been writing stuff like this:
Underdetermination regarding which math or model to use does seem related by some thinkers to incompleteness, rejected by others & some here.
Math studies found inherent incompleteness, PM studies found inherent incompleteness, HPS studies found incompleteness.
Although the incompleteness Gödel proved in his incompleteness theorems
is related to the fact that first order axiomatizations of arithmetic fail to rule out non-standard models, I now realize you have no idea what that means.
You seem to think you can understand Gödel's theorems in terms of English dictionary definitions of words like "underdetermination", "completeness", and "incompleteness". As you have demonstrated, understanding Gödel's theorems on that level is worse than not understanding Gödel's theorems at all.
This comment suggests no distinction between the content of the theorems (about which I've consistently declared my complete ignorance) and their value to illustrate an important epistemological truth in scientific development efforts.
You do indeed appear to be completely ignorant of what Gödel's theorems say. That you regard your complete ignorance of those theorems as an adequate foundation for using them "to illustrate an important epistemological truth in scientific development efforts" is mind-boggling.
Arguments against math claims I don't make, cannot make, have not made, and repeatedly declared that I've not made them - these arguments seem emotionally motivated and quite misguided. If one wishes to show that the principle of incompleteness appearing in multiple fields by multiple means absolutely cannot be considered a plausible clue for directing research, then it seems one should try to make that case.
You're free to regard "the principle of incompleteness appearing in multiple fields by multiple means" as "a plausible clue for directing research", but claiming Gödel's theorems as support for that approach is clueless.
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The technical meaning of "completeness" and "incompleteness" in Gödel's theorems[/size]
Gödel's theorems are a bit confusing because the technical notion of completeness used in his completeness theorem is not the same as the technical notion of completeness used in his incompleteness theorems. In Gödel's completeness theorem, the intuitive meaning of "completeness" is that it's possible to write down an algorithm for proving all valid theorems; in modern terms, Gödel's completeness theorem says it's possible to write a certain computer program (which is only moderately difficult to write). In Gödel's incompleteness theorems, the "incompleteness" means there's a formula such that neither it nor its negation is provable.
To simplify my explanation of Gödel's theorems and to make them more accessible to computer-literate readers, I'm going to rely upon the modern theory of formal languages and automata.
A
formal language is a particular set of strings formed from the characters in some finite alphabet. The set of all sentences (well-formed, closed formulas) of first order logic is a formal language. The set of all sentences of first order Peano arithmetic is another formal language.
An
automaton is the mathematical idealization of a computing device.
Turing machines are the kind of automata that's most relevant to Gödel's theorems, but there are many other interesting kinds of automata, including finite state machines and pushdown automata.
Automata are related to formal languages in the following way: When given a string s that might or might not belong to some formal language L, an automaton M can do one of three things:
- It can accept the string s.
- It can reject the string s.
- It can do something else (go into an infinite loop, get stuck, blow a fuse, ...)
An automaton M is said to
recognize a formal language L if and only if M accepts every string in L and does not accept any strings that are not in L. (Note well that M does not have to reject strings not in L; it just has to avoid accepting them.)
An automaton M is said to
decide a formal language L if and only if M accepts every string in L and rejects every string not in L. If M decides L, then M also recognizes L, but the converse is not necessarily true.
Using those modern definitions, we can state modern versions of Gödel's theorems and related results. To state those theorems, we'll need the highly technical definition of what it means for a formula to be
true in an
interpretation. I'm going to omit those definitions, but I will mention that Alfred Tarski defined this notion of "true" using essentially the same techniques that are used today to define the
denotational semantics of some programming languages.
ETA: A sentence is valid if and only if it's true in all interpretations.
Gödel's completeness theorem. There exists an automaton M that recognizes the language consisting of all valid first order sentences.
Church's theorem. No automaton decides the language consisting of all valid first order sentences.
Undecidability of arithmetic. No automaton decides the language consisting of all first order sentences of arithmetic that are true in the standard interpretation.
On 21 November 2013,
I defined two formal languages that are proper subsets of the set of all first order sentences of arithmetic that are true in the standard interpretation. One of those formal languages is Q, which consists of the ten axioms of Q together with their logical consequences. The other formal language is P (for first order Peano arithmetic), which consists of the ten axioms of Q together with the infinitely many instances of the first order induction schema, plus all logical consequences of those axioms.
Gödel's first incompleteness theorem. If
- A is any set of axioms for which some automaton decides A, and
- T is the set of logical consequences of A, and
- T contains Q as a subset, and
- T is consistent,
then there exists a true sentence of first order arithmetic that is not an element of T and whose negation is also not an element of T.
ETA:
Corollary. No automaton recognizes the language consisting of all first order sentences of arithmetic that are true in the standard interpretation.
For the following version of Gödel's second incompleteness theorem, we need a highly technical definition of Consis(M), which is a sentence of first order arithmetic that says a certain theory is consistent (contains no self-contradictions). That highly technical definition amounts to a computer program that, given the description of an automaton M that decides the set A of axioms for the theory T in question, produces a particular consistency sentence for T as its output. In my statement of the theorem, the consistency sentence produced from M is written as Consis(M).
Gödel's second incompleteness theorem. If
- A is any set of axioms for which some automaton M decides A, and
- T is the set of logical consequences of A, and
- T contains P as a subset, and
- T is consistent,
then Consis(M) is not an element of T.
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What this has to do with BurntSynapse[/size]
With those definitions and theorems in mind, I invite
BurntSynapse to take another look at my counterexamples to his claim that "completeness for rules governing the application of rules can never be totally documented, it must be assumed."
If history is any guide, and it has been heretofore, I'm sure
BurntSynapse will find this entire post irrelevant to his claim.
And this post of mine may very well be irrelevant to BurntSynapse's claim. If so, then
BurntSynapse was using the word "completeness" to mean something very different from what that word means in Gödel's theorems, and my mistake lay in assuming
BurntSynapse possessed any understanding of what that word means in the context of Gödel's theorems.