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Yes, if they have a known vulnerability in the wild in a currently-supported product, the rest is just details.

Tangentially, I wonder: has anyone built a friendly browse/search interface for all-time CVE data [0]? This makes me curious about what the history of SQL injection vulnerability discovery looks like.

0: https://cve.mitre.org/data/downloads/index.html


This is great. People who don't trust experts and cynically think that everything is political can readily say "It's really cold! See, global warming and climate change are fake!" Here we see that the polar vortex isn't extra-strong this year, it's extra-week, and the breakdown may send chunks of it southward.

This armchair level of understanding (even if my summary is not right on the nose) is what we need when we encounter people who actually want to politicize the weather. Will we defeat ignorance, or will ignorance defeat us?


> Will we defeat ignorance, or will ignorance defeat us?

It's not ignorance that's the problem. The people orchestrating global warming denialism aren't stupid - they are just cynically self-serving.


Then stop using the word global warming, poor marketing, when it gets cools(which it will) instead of warm it starts to look and sound a con. The more enlightened skeptics are more so "human caused" climate change skeptics than anything else, with the sun as their main point of origin.


Agreed, "global warming" is poor marketing. It's also a common colloquialism among climate change deniers, no? So, if you need to explain to someone how cold weather doesn't mean "global warming is fake", maybe also steer them toward the notion of climate change. "Anthropogenic forcing" or "it's our fault" is of course another important matter.


Is it one or the other? I don't know anything about dark rooms where captains of industry who profit from fossil fuels orchestrate climate denialism. Sounds plausible. But in any event, such efforts are surely more difficult, if possible at all, with an informed citizenry.


For some reason, I have a PhD in Health Policy and clinical practice, so, I'm inclined to look at the healthcare system when thinking about this question.

IMO it's simple (and this is of course a common view): healthcare in the United States is a failed market. It's not about free market fundamentalism vs socialism, it's just that in this case, this market is totally broken. Costs are completely out of control, and accordingly, access, that is, access without incurring crippling debt, is a huge problem.

Obama tried to address both cost and access. He went up against the insurance companies, and lost. He got somewhere on access, but even that is just access to insurance; insurance that may leave you with thousands of dollars to pay out-of-pocket if you walk into the ED with a complaint. So maybe you don't go.

Socialized medicine, it seems, certainly won't fly in this country. But socialized insurance, "Medicare for all"? We, the little people, have many reasons to support a multi-decade experiment with that.

There's no ideology here. It's just insane (unless you're profiting!) given history for us to continue imagine that in this case the Invisible Hand is going to fix things.


> Socialized medicine, it seems, certainly won't fly in this country. But socialized insurance, "Medicare for all"?

The same endless propaganda and sloganeering brought to bear against socialized medicine in every medium and from every mainstream politician to make us think that it's obviously an impossibility in the US (because reasons), is used against Medicare for all. The possibility of changing US healthcare has never had a relationship with any potential improvement in health outcomes or lowering of costs - the chance for any new plan relies on how well it preserves the profits of an industry that consumes twice the proportion of GDP here as it does in any other country.

One of the reasons M4A is criticized has been that it doesn't directly lower anything except administrative overhead (which is massive, but trivial in comparison to the difference between US health care costs and the costs of the civilized world, which would have kept the US in budget surpluses year after year.) It relies on government to put pressure on prices. As the industry's only customer, it would obviously have the leverage, but with most individual politicians being funded by the industry, there's no expectation that it would suddenly have the will. M4A is criticized for not being socialized medicine (i.e. an NHS-like program) by interests who are also against socialized medicine.

The reason Obama passed ACA is because it preserved industry profits, stalled the growth in the rise of healthcare costs, and would hopefully delay the next mass challenge to the status quo. At the beginning of the 2020 election cycle, popular pressure led to virtually all of the early Democratic primary lineup to feign support for M4A, and by the end of the cycle it wasn't even in the platform as an aspirational goal, despite the VP-elect owing her entire initial media presence from her (later-reversed) support of Sanders' bill.

Getting M4A passed will likely be as difficult as getting socialized medicine passed, and would require immense and focused public pressure. We had the most popular candidate in the country run on it as a central issue twice, and during the second time, a new virus changed everyone's daily lives in the middle of the election. Still, through the media, it became a referendum on the personality of a reality show host, Russian spies, and secret pedophile networks. Rational healthcare policy has no hope.


Aviation accounts for 1.9% of global greenhouse gas emissions [0]. If we're going to take a sober look at where to focus our efforts, this:

"Global aviation’s contribution to the climate crisis was growing fast before the Covid-19 pandemic, with emissions jumping by 32% from 2013-18"

Should be:

"Global aviation’s contribution to the climate crisis was growing fast before the Covid-19 pandemic. Aviation's contribution to global CO2 emissions rose from 1.3% to 1.9% from 2013-18"

But the latter doesn't attract clicks so much. Transportation overall accounts for 28% of greenhouse gas emissions [1]. That's the story that matters.

There's certainly a point here about wealthy nations and wealthy people being responsible for a lion's share of the problem, but really, everyone knows that. This article, and indeed the linked paper [2] gloss over the relative size of the aviation problem.

[0] https://ourworldindata.org/co2-emissions-from-aviation

[1] https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emis...

[2] https://www.sciencedirect.com/science/article/pii/S095937802...


If you restrict yourself to the part of the world that can actually afford to fly, aviation looks quite a bit worse. Taking a trip from Europe to California is a good way to basically double my carbon footprint for the year.

Aviation is also fairly unique in that we don't know how to make it climate neutral. Even burning synfuel made from renewables won't be enough, because adding emissions higher in the atmosphere has a stronger warming effect. And we just don't know how to make all-electric long distance planes yet.


> Even burning synfuel made from renewables won't be enough, because adding emissions higher in the atmosphere has a stronger warming effect.

It has a temporary strong effect, that falls back into the normal one in a couple of decades. What means that synfuel based aviation would have a constant impact on the global temperature, like painting your ceiling black. We can live quite well with that.


Yes, or (in this case?) interpreting it. I think of spreadsheets as visual functional programming environments. The humble spreadsheet has an interesting kinship with the most trendy, and, for some (me!), difficult-to-grok programming paradigm.


YES! This is exactly how I see it. I feel like I'm in this weird intersection of people who've spent A LOT of time in Excel and also significant time in programming to feel this way about spreadsheets but I don't know who else to talk to..

I tried making the same point on reddit the other day

https://www.reddit.com/r/excel/comments/jpb2ud/edit_a_spread...


The soon-to-come LET function agrees :)

https://support.microsoft.com/en-us/office/let-function-3484...

Disclaimer: I work at Microsoft


That's awesome. So you basically allow implicit creation of off-spreadsheet named cells (sub-cells, in a sense, as they're only locally available). Very useful.


See also "Spreadsheets: Functional Programming for the Masses" by Simon Peyton-Jones et al.


TLS not E2E. When Zoom got called out for lying about having E2E [0], I looked into the landscape around this a bit. Facetime and Signal are E2E, but don't support recording, which would of course need to be on-device if implemented.

Does the distinction matter? I think so. There's a big difference between the provider promising to keep your data secure and to not do anything underhanded with it versus the provider simply not having access to your data.

[0] https://www.theverge.com/2020/3/31/21201234/zoom-end-to-end-...


Really, a ding here? I thought HN was where you go to discuss what's actually going on under the hood, not so much "now you need a Google account", which will surface itself in your general tech news feed. Hmm. I hope we don't go the way of Slashdot. What a sad decline that was. Where Google comes down on TLS vs E2E is a BFD.


If I'm teaching young'ns per se using a toy language, I'd reach for Scratch. It's history and Google's embrace of it seem like strong endorsements. Are there other good candidates in that space?

If I'm teaching an intro class using a general purpose language, it's Ruby or Python. My heart lies with Ruby, but having basic Python chops is such a bigger win downstream.

  for i in range(1, 101):
      if i % 15:
          print ('FizzBuzz')
      elif i % 3 == 0:
          print ('Fizz')
      elif i % 5 == 0:
          print ('Buzz')
      else:
          print (str(i))

  (1..100).each do |i|
    if i % 15 == 0
      puts 'FizzBuzz'
    elsif i % 3 == 0
      puts 'Fizz'
    elsif i % 5 == 0
      puts 'Buzz'
    else
      puts i
    end
  end


  (1..100).each do |i|
   puts case
     when i % 15 == 0
       'FizzBuzz'
     when i % 3 == 0
       'Fizz'
     when i % 5 == 0
       'Buzz'
     else
       i
     end
   end


Yes, cleaner, and no switch in Python.


(offtopic) You might be missing an '== 0' in the second line there? I've never done fizzbuzz so I honestly don't know, but the ruby version has it.


Zero and empty lists and dictionaries are treated as False in Python.


If you're uninitiated and simply want to grok where true-but-unprovable comes from, I recommend: https://www.quantamagazine.org/how-godels-incompleteness-the...

Wolchover is masterful here. The layers of abstraction keep piling up, and I had to read the last part more than a couple of times to really get it, but then you have it.


Just going to echo @dwohnitmok here in saying that this is a pretty 'meh' article. Understanding Godel's First Incompleteness Theorem is actually very accessible, I wrote about it a few years ago[1]. His second is much more involved and laymen won't have the required tools to grasp it. In my opinion, the easiest way to understand it is probably using Löb's Theorem, but that's neither here nor there. Either way, I'm of the opinion that arithmetic coding is very confusing and shouldn't be used to introduce people to Godel.

[1] https://dvt.name/2018/03/12/godels-first-incompleteness-theo...


I'm not sure this is equivalent to Gödel's theorem. Actually, I'm not sure this is a correct proof of anything at all, merely a sort-of demonstration of Richard's paradox.

First, for reference, let me quote First Incompleteness Theorem: "Any consistent formal system F within which a certain amount of elementary arithmetic can be carried out is incomplete; i.e., there are statements of the language of F which can neither be proved nor disproved in F." (from Wikipedia)

Now back to your post.

Obviously, f' is not in T and it is not computable. But neither is T. It is incomputable merely by being the list of computable functions, which we cannot construct because of halting problem and stuff like that.

And your definition of f' relies on having T. So we don't in fact have seen "statement f'". So, the direct connection between Gödel's theorem and your construct is not obvious to me, because first is about constructable, but unprovable statements, and second seems to be a faulty (i.e. mathematically uninterpretable) construct itself.


> I'm not sure this is equivalent to Gödel's theorem.

It is. In fact, I've seen it proven this way several times (mostly in CS-y papers), but it's definitely not common. My post is in fact based (almost beat-by-beat) on this UC Davis lecture: https://www.youtube.com/watch?v=9JeIG_CsgvI


Your plain and confident statement "it is" doesn't really address any of my concerns, and I just explained why, as it seems, it actually isn't.

P.S.

I did some random googling, and while I'm not sure, all this story seems to be based off of Paul Finsler's work, which he himself thought to be the priority for an incompleteness theorem (Collected Works Vol. IV., p. 9), but didn't seem so to Gödel (and, seemingly, the majority of those who had to say something about it).

If this indeed is the same thing, it would explain to me why this "proof", which doesn't seem to me like a proof at all is so widespread. But, again, I'm not sure I'm reading into it correctly, and operating under assumption that if somebody could provide something more weighty than "it is" statement, I could be persuaded otherwise.


> Your plain and confident statement "it is" doesn't really address any of my concerns...

Your concerns aren't really valid (for example, the computability of T is irrelevant). These are questions I already answered before on both HN and in the Disqus comments. Further, metalogic was my area of focus in school, so I'm quite familiar with intricacies here, and don't really feel it's useful to get too deep into the weeds. But don't take my word for it; Dr. Gusfield's paper (that the lecture is based on) can be found here: https://csiflabs.cs.ucdavis.edu/~gusfield/godelproofreviseda...

The ideas in this proof have been well-tread by Scott Aaronson, Peter Smith, and Michael Sipser. My curt "it is" is also meant to nip in the bud -- correct -- claims that it's not exactly what Godel proved (the OG variant is actually slightly stronger). Why I'd want to nip these in the bud is that in school, you technically learn the weaker variant (albeit starting with a Henkin construction of Godel's Completeness Theorem). Sort of like this[1]. But the difference between the two is so nuanced, it's not even really worth bringing up unless we're in a graduate seminar.

[1] https://hal.archives-ouvertes.fr/hal-00274564/document


Per the end of your article, have you started writing about the 2nd theorem yet?


I did (https://dvt.name/2018/04/11/godels-second-incompleteness-the...) -- but like I mentioned, it's not very accessible and I don't think it's a particularly good explanation, either (although I've yet to find one I really like, to be honest).


The article plays a little fast and loose with language

> For example, Gödel himself helped establish that the continuum hypothesis, which concerns the sizes of infinity, is undecidable, as is the halting problem

The continuum hypothesis is definitely not "undecidable" in the same way that the halting problem is undecidable. Though there are deep connections behind the two, the two notions of "undecidability" (logical independence in the former and Turing machine computability in the latter) are very different.

Also,

> He also showed that no candidate set of axioms can ever prove its own consistency.

This is powerful as a limiting result, but it has little direct impact for philosophy, because you wouldn't trust the consistency result of a system you suspect might be inconsistent to begin with because inconsistent systems can prove anything. So saying "my axioms prove themselves consistent" shouldn't have increased your trust in those axioms to begin with in the absence of the incompleteness theorems.

I'm not really a fan of "true-but-unprovable" as short-hand the incompleteness theorems, because that hinges a lot on what kind of logic system you're in and how that logic system defines "truth" (taken at face value, how do we know that Godel's incompleteness theorem is "true?").

I prefer rather to pose two questions to reflect on that I think illuminate Godel's incompleteness theorems some more. Most modern logical systems (e.g. first-order logic and its various extensions and variants) equate unproveability with logical independence. So with that in mind, here's two questions.

First, Conway's Game of Life:

Conway's Game of Life seem like they should be subject to Godel's incompleteness theorems. It is after all powerful enough to be Turing-complete.

Yet its rules seem clearly complete (they unambiguously specify how to implement the Game of Life enough that different implementation of the Game of Life agree with each other).

So what part of Game of Life is incomplete? What new rule (i.e. axiom) can you add to Conway's Game of Life that is independent of its current rules? Given that, what does it mean when I say that "its rules seem clearly complete?" Is there a way of capturing that notion? And if there isn't, why haven't different implementations of the game diverged? If you don't think that the Game of Life should be subject to Godel's Incompleteness Theorems why? Given that it's Turing complete it seems obviously as powerful as any other system.

Second, again, in most logical systems, another way of stating that consistency is unproveable is that consistency of a system S is independent of the axioms of that system. However, that means that the addition of a new axiom asserting that S is either consistent or inconsistent are both consistent with S. In particular, the new system S' that consists of the axioms of S with the new axiom "S is inconsistent" is consistent if S is consistent.

What gives? Do we have some weird "superposition" of consistency and inconsistency?

Hints (don't read them until you've given these questions some thought!):

1. Consider questions of the form "eventually" or "never." Can those be turned into axioms? If you decide instead to tackle the question of applicability of the incompleteness theorems, what is the domain of discourse when I say "clearly complete?" What exactly is under consideration?

2. Consider carefully what Godel's arithmetization of proofs gives you. What does Godel's scheme actually give you when it says it's "found" a contradiction? Does this comport with what you would normally agree with? An equivalent way of phrasing this hint, is what is the actual statement in Godel's arithmetization scheme created when we informally say "S is inconsistent?"

At the end of the day, the philosophical implications of Godel's incompleteness theorems hinge on whether you believe that it is possible to unambiguously specify what the entirety of the natural numbers are and whether they exist as a separate entity (i.e. does "infinity" exist in a real sense? Is there a truly absolute standard model of the natural numbers?).


Who cares about the philosophical implications of the theorems? Philosophers! The linked article is about how the theorems destroyed Whitehead et al's aspirations to find One Algebra To Rule Them All.

The literature on Gödel and philosophy is gargantuan, for some reason. Wasn't it summed up well by Wittgenstein? Paraphrasing: "Who cares about your contradictions?" Well said. Also not the topic Wolchover's article.

Math people can make the same move: "Who cares about your philosophizing?"


> The linked article is about how the theorems destroyed Whitehead et al's aspirations to find One Algebra To Rule Them All.

Sort of. Whitehead's contributions to universal algebra are still relevant and universal algebra is still a thriving field of study for mathematical logic. Although perhaps you mean "algebra" in a more informal sense?

Again, the conclusion of the article is a bit strong.

> Gödel’s proof killed the search for a consistent, complete mathematical system.

The consistency half doesn't make sense. (EDIT: I get it now, see the last sentence of this paragraph) There was never a search for a consistent mathematical system in the sense that Godel destroyed because again a system that can prove its own consistency has no positive value in evaluating the consistency of that system (Godel's big contribution here is contributing a strong negative result, if it could prove its own consistency you're pretty screwed). EDIT: On reflection I see that the sentence probably means to tie consistency to completeness rather than as a stand-alone quality. That makes more sense.

As for mathematicians, their reactions to Godel's incompleteness theorems overall are probably similar to "Who cares about your incompleteness theorems?" (there's a reason Russell and Whitehead are known primarily for being philosophers first and mathematicians second and why often times there is distinction between logicians like Godel and other mathematicians). Most mathematicians don't think about the foundations of mathematics because it is (perhaps surprisingly) largely irrelevant to the day-to-day work of mathematicians. Indeed the vast majority of mathematics is very resilient to changes in its underlying foundations.

To interpret Godel's incompleteness theorems requires a healthy dose of at least mathematical logic that can start veering quite close to mathematical philosophy.

An example from the article:

> However, although G is undecidable, it’s clearly true. G says, “The formula with Gödel number sub(n, n, 17) cannot be proved,” and that’s exactly what we’ve found to be the case!

Well no, that's not true in certain senses. Indeed in a larger axiomatic system subsuming the current system that corresponds to G, it is completely consistent to state that G is provable and that its statement is provable (see my example of S'), i.e. there are Godel numbers that correspond to both a proof of G and to a proof of its content. To interpret that statement that way requires certain philosophical commitments to the correspondence between a Godel number and truth, which not everyone would accept (do you accept the truth of the new axiom introduced by S'? Why then do you accept the truth of the statement "S is consistent?" and vice versa).

"In striving for a complete mathematical system, you can never catch your own tail." This on the other hand I think is a very good informal description of what's on with Godel's incompleteness theorems. Focus on the incompleteness not on truth.

That's why I'm not a fan of using the word "truth" when talking about Godel's incompleteness theorems. I am in fact deeply sympathetic to your desire to separate philosophy from Godel's incompleteness theorems.

I prefer to clearly delineate between its logical properties in mathematical logic and its philosophical implications and using the word "truth" by necessity muddles the two.

FINAL EDIT: I am being perhaps a bit too harsh on the article. I think it does a fine job of describing the arithmetization of the incompleteness theorems. But if someone else reading this also decides to create an informal guide to Godel's incompleteness theorems, please please please don't use the word "truth" and "true" or at least separate it out into its own section on philosophy.


> that's not true in certain senses

I think it's not true in a very clear sense: you can construct semantic models of the axioms of arithmetic in which it is false. In other words, you can construct semantic models of the axioms of arithmetic (more precisely, of the axioms of arithmetic using first-order logic, which is what the article is about) in which there is a "number" that is the Godel number of a proof of the Godel sentence G! Godel's Theorem just ensures that in any such model, the "number" that is the Godel number of such a proof will not be a "standard" natural number, i.e., one that you can obtain from zero via the application of the successor operation.

So another way of viewing this whole issue of "truth" is that it is always relative to some semantic model. If your chosen semantic model of the axioms of arithmetic is the "standard" natural numbers, and only those numbers, then the Godel sentence G for that system will be true--there will indeed be no number in your model that is the Godel number of a proof of G. But if you pick instead a non-standard model that includes "numbers" other than the standard natural numbers, but still satisfies the axioms, then the Godel sentence G can be false in that model, since there can exist a "number" (just not a standard one) in that model that is the Godel number of a proof of G.


What you are saying is true (as you allude to with first-order logic) in any context in which Godel's completeness (not incompleteness) theorem holds. Not all logics have versions of Godel's completeness theorem (e.g. second order logic with full semantics). You can argue that philosophically in systems where Godel's completeness theorem fails that the article's statement is valid. But yes that's why it's only true in "certain senses."

More generally the philosophical question of truth revolves around whether there is a single, true set of standard natural numbers that corresponds to reality, and therefore all nonstandard natural numbers are "artificial" in some sense, or whether even standard natural numbers exist only in a relative sense.


You seem like somebody who I could ask some (2) questions on the topic.

1. First of, I'm still not sure what to make of Gödel's theorems philosophically. In the "pop-culture", so to speak, there seems to be a notion that Gödel's theorems are, in essence, some grand, weighty statement about fundamental "inaccessibility of truth". That since Peano's arithmetic exemplifies very simple (compared to our general needs) mathematical system, no matter how we further develop math, one day there will be a useful, meaningful statement which cannot be proved or disproved.

What's perhaps even worse, some people, even some with names I feel uncomfortable to argue against (Penrose, for example, seems to be of this opinion) try to use it as a transition to the idea that "human mind is more than a computer", which I always implicitly assumed to be just a manifestation of anthropocentric hubris. The key to their reasoning is the observation, that some expressions unprovable within some formal system are "obviously true" (and they often kinda are, and they are provable within a higher-order formal system). So, the story goes, since the Turing machine couldn't see it (because of Gödel's), but we see it, we are more than a Turing machine.

And since that informal version of Gödel's findings was familiar to me long before I was acquainted with a formal version of it, I'm kinda used to the idea that "it must be right".

However, when I'm looking at the formal explanation of Gödel's theorems, or even perhaps more interesting "applied" findings, based on them (like Goodstein's theorem), they all seem to be surprisingly "boring" and non-consequential clever tricks based on self-referencing. I mean, it's sure a very interesting finding about formal systems as such, but if we take a step back into the realms of common sense: isn't it rather quite intuitive, that a system cannot be proven to be consistent by the means of the same system? So it must be of no surprise that any formal system powerful enough to be able to express statements about consistency of itself must be "incomplete".

So, my question is, am I missing something? Is there any truth to that pop-cultural image of Gödel's theorems? Because to me it seems like there actually isn't, just more of an "urban myth".

2. Continuum hypothesis. As I understand it, it is a matter of axiom, if 2^Aleph₀ ?= Aleph₁ and |R| could be as well Aleph₅ or whatever. Of course, we have most natural axiomatic system (with axiom of determinacy) where the former is true. But are there, like it was with Euclid's fifth postulate, any alternative, but still "interesting" constructs? Is there any use whatsoever in the assertion that continuum hypothesis is false?


I'll give brief statements with lots of hand-waving since I'm low on time. These are long questions.

1. In short, this is a deeply philosophical question. My personal inclination follows yours that the incompleteness theorems are overhyped. I don't buy Penrose's argument. Like most other formal limiting results philosophically I view those results as representing fundamental limits of both human and machine reasoning. While a single unproveable but "obviously true" result generally point to an inadequacy of the formal system, if every formal system suffers from some inadequacy that is indicative of a limitation in the fundamental human faculties of comprehension rather than a limitation of formal systems per se (the assumption e.g. that our formal systems must use finitistic methods is one born of human limitations and, depending on one's thoughts about the universe, potentially fundamental physical ones).

There are philosophically defensible positions that try to claim the incompleteness theorems have implications for truth in the real world, but I go back and forth on whether I believe them and more to the point they are far more subtle than the usual pop culture presentations of Godel's incompleteness theorems.

2. The mathematical Platonists I've come across believe that the continuum hypothesis is in fact false. (As an aside it's interesting that you find the axiom of determinacy natural as it contradicts the axiom of choice.) This mainly hinges on your opinion of the reality of large cardinals (which perhaps count as your "interesting" constructs), which many Platonists for a variety of reasons believe to be real.


Very interesting remarks... never looked at it in this way. Thx!

Care to write a short but more explicit wrap up of how you see your two questions yourself?


Don't read this without thinking about the questions first!

I tried to be short... there's a considerable amount of handwaving. I'll present two components to each of my answers. One that stays within mathematical logic and then one that expands a bit into philosophy.

1. Strictly mathematical logic: Godel's incompleteness theorems can be viewed as a limiting result on the absoluteness of mathematical induction (this is not strictly true, in fact we lose even more than absoluteness of induction, see e.g. Robinson's Q, but I'll leave that aside for now). Conway's Game of Life rules are complete in the context of a single step. That is for any step n, Conway's Game of Life rules completely determine step n + 1. The assumption that given a fixed starting state, this means that Conway's Game of Life is completely determined for all steps is exactly a statement of mathematical induction. In particular, we are piggy-backing off of the induction axiom of Peano arithmetic here. That's where Godel's incompleteness theorems get you.

One way of thinking about Godel's incompleteness theorems is that they attack the assumption that because we have defined every step transition we have defined the whole process. Hence certain "global" statements about potentially unbounded processes remain up in the air. Even if we rule by fiat with an induction axiom (or axiom schema) that this must be true, some ambiguity remains. "After a certain point once this square turns white it never turns black again" or "this square will never turn white" are both statements that are independent of Conway's Game of Life rules for certain squares and starting configurations.

Now this ambiguity is not observable because while we have ambiguity for unbounded questions, as soon as we place any bound, no matter how large the n (e.g. for the next 1000000 steps this square will not turn black), there is no ambiguity. Incompleteness hinges essentially on the ability to make unbounded statements which involve the words "eventually," "always," "never," etc.

Now the philosophical implications of this are interesting. This question is why I'm skeptical of naive attempts to talk about the incompleteness theorems' consequences for physical theories of the universe. Intuitively I view physicists as trying to find the "Game of Life" rules for the universe, and that if they did, that would be as good a candidate as any for a "theory of everything." In particular these rules would be local and finite, rather than global, infinite statements of the sort I outlined above. If you're willing to accept Conway's Game of Life as being complete enough for your purposes, I would argue you should accept a similar "theory of everything" as being "complete enough."

Now there's no reason why Mother Nature must be kind enough to furnish us with such a theory, but that's a different story.

Another interesting philosophical component here is whether this implies Godel's incompleteness theorems have any meaningful physical manifestation. I don't have the time at the moment to get into that discussion, but suffice it to say I generally think that these discussions usually go off the rails really really quickly without a deep understanding of the incompleteness theorems rather than informal overviews of them. In the philosophical context of Conway's Game of Life, you'd expect to find deviations in different implementations of the the rules "after an infinite amount of steps have passed." Whether you find that a coherent statement or not has implications for the applicability of Godel's incompleteness theorems to the physical universe.

EDIT: To tie this to the hints I gave, unbounded statements involving words like "eventually" or "never" are precisely those statements that can be independent of the "axioms" of the Game of Life. When we talk about the completeness of the Game of Life we are talking about it only at a per-step level.

2. Godel's incompleteness theorems are ultimately statements about natural numbers, or at least what the current logical system in question thinks is a natural number. The interpretation that this natural number represents some logical statement is a metalogical one and unjustified within the logical system itself. We can only make this interpretation as an outside observer. So S' produces a "number" according to the algorithm we use to represent the statement of inconsistency of S. However, within S' this is just a number. It doesn't know how to turn that number into a logical contradiction that it can then produce and use to prove things. As an outside observer then we are either free to agree with S' that indeed yes what you've produced is a number and then use that number to deduce the inconsistency of S or we can disagree with S' that this number represents an inconsistency of S (informally, you can imagine that S' is "hallucinating" a number that while might be a natural number according to the axioms of S', is not a natural number according to ours as an outside observer).

If we have a notion of what the "true" natural numbers are, as opposed to natural numbers are "hallucinated," we can talk about whether S' is right about the consistency of S. The assumption that S' is not "hallucinating" natural numbers is known as omega-consistency (https://en.wikipedia.org/wiki/%CE%A9-consistent_theory). Whether "true" natural numbers exist... well that brings me to the philosophical ramifications.

If you believe that there is one true set of natural numbers then it's easy to dismiss S' as a trick, useful for proofs and exploration, but ultimately simply an interesting tool rather than reflective of reality. If you believe that there is no such thing as "one true set of natural numbers" then consistency is simply a relative statement.

EDIT: To tie this to the hints I gave, Godel's arithmetization scheme only gives you numbers. It's up to you the reader to interpret those as proofs and logical statements. Within certain bounds, you are free to disagree that in your interpretation that this number represents a valid proof (or in equivalent phrasing that this "number" is truly a number).


Thanks! I'm bookmarking this to come back to for a while :-)


May I suggest that "true" in "true-but-unprovable" means from God's eye or in a higher level system but not in current system because "unprovable"(in current system only) means it's not really true in current system? Correct me if I'm wrong in this context.


You are wrong. Godel in fact showed precisely that there are unprovable statements in any consistent set of axioms. In fact it’s equivalent. The only systems in which every statement is provable are inconsistent. Consistent here meaning that statements cannot be proven to be both true and false from axioms.


There are two other conditions/premises that, arguably, play a bigger role in Gödel's theorems:

1. The theory must be strong enough to do a certain amount of arithmetic

2. The axioms of the theory must be computably enumerable

So, you can have relatively weak theories in which the incompleteness results don't hold. A major example here is comes from Gödel's _completeness_ theorem (notice "completeness" not "INcompleteness") which says: in first-order logic a statement is true if and only if its provable.

You can also have strong theories whose axioms are not computably enumerable. Start with something like the Peano axioms and consider the set of all true statements in that theory. We can take any set we want as axioms, so what if we take the set of all true statements in Peano arithmetic as our axioms?

Now every valid "proof" is one line long since what was previous a theorem is now an axiom, but we've kicked the can down the road. How do we figure out whether something is an axiom in this new system or not?

This latter system is called "true arithmetic" Gödel's incompleteness theorems don't apply there, either.


Godel's completeness theorem is not in opposition to his incompleteness theorems.

Godel's incompleteness theorems and completeness theorem can hold at the same time. They talk about two separate notions of completeness (the former about incompleteness in the sense of logical independence and the latter in the sense of the correspondence between semantics and syntax). Indeed Godel's incompleteness theorem is usually presented in the context of first-order Peano arithmetic.

This is again why I don't like talking about "truth." It is not completely inaccurate to say Godel's completeness theorem says "a statement is true if and only if it's provable." It is also not completely inaccurate to say Godel's incompleteness theorems say "some true statements are not provable." But the vagaries and philosophical baggage behind the two statements mean you have to tread _very_ carefully and without _extremely_ careful qualifications you can start making philosophical statements that are extrapolations of those theorems rather than the theorems themselves. That's why I strongly believe that it's much much much more productive to talk about incompleteness and consistency rather than truth.


You're right! I confused the deductive system/language w/ the theory. Oops.

Something like Presburger Arithmetic would've been a proper example.


I'm not contradictory to your statement. Or your explanation hasn't touch my potential flaw if exists. Let me put in this way:

There is at least some "thing" that can not be proved without cause inconsistency. To avoid the inconsistency to prove the "thing" which become true we need to create a high order system in which then the "thing" is truth but also cause the same dilemma in the new bigger system that new "thing" will show up that need another high order system. So it's correct that no system can contain all truth while keeping consistent. This is the point you want to express in your statement, right? (Actually it's Godel theorem in plain English itself)

What I try to say is: if its not provable in current system so it can not be called true within current system. I could be wrong at this part but not what you tried to explain which I already agree.


This isn’t quite right, though perhaps a nit, plenty of formal systems are provably sound (only true things are provable) and complete (all true things are provable). For example, the predicate calculus you learn in Logic 101. Formal systems become provably incomplete when they are able to express arithmetic (e.g., Peano axioms).


Thanks for the link, it was a joyful read.


Hear here! I'm reminded of Freud's "Civilization and Its Discontents", wherein he expands his ideas about psychopathology to civilization as a whole. Tellingly, psychologists call what what you describe "splitting"[0], and, increasingly, that's what society is doing in the United States.

[0] https://en.wikipedia.org/wiki/Splitting_(psychology)


Maybe someone here can explain: I've come across more than a few philosophers, of the PhD/academic flavor, who are dismissive of Wittgenstein's work. I have a gist-level understanding of his work, and a hobbyist's knowledge of the history of Western thought up through, say, Foucault.

Am I seeing a biased sample or is LW out of fashion these days? If so, why?


Here's my take on it. Academic philosophy in the US is highly focused on making completely clear claims with a rigor approaching that of mathematical logic. It is more or less pursuing the program Wittgenstein sketched in his first book, the Tractatus, creating a collection of concepts and network of relationships among them in which apparent philosophical paradoxes vanish. This is the analytical tradition. It is nice because it is indeed rigorous, but it can be limiting because it severely constrains the topics you can talk about. Something as big and multifarious as, say, Heidegger's notion of Dasein does not fit into this mold. And certainly nothing written as poetically as Nietzsche would pass muster.

In his second book, Philosophical Investigations, Wittgenstein completely rejected this approach, and his earlier work. He claimed that....well, no one's really sure what he claimed, or that he really claimed anything, and that's exactly the problem academic philosophers have with him. To a first approximation, he claimed that the whole idea of language as a formal system was either wrong or a waste of time, and that language is better thought of as some kind of game.

The thinking, then, is that later Wittgenstein was not making a clear point, was not interested in making a clear point, and possibly was not even serious at all. Philosophical Investigations is an enigma, and modern academic philosophy doesn't deal in such things.


I've never felt enticed to read a book by any philosopher, but that kind of made curious!

Especially given the comment about language could be seen as some kind of game, about which I'd say he's at least then partially been shown to be right? Being understood is very much a game, as you without anticipating your counterparts expectations and knowledge are often hopefully lost. Though I don't know if that's even close to what he was referring to, so yes, a but curious.


The idea of a "language game" was merely an analogy. It wasn't meant to trivialize the subject. The point is that language is an activity that operates according to conventional rules. (This also relates to his argument against "private language", though I'm personally not as convinced by that.) If you were to give a short summary of Wittgenstein's philosophy, I think it's better to say that he claimed meaning is use. "For a large class of cases—though not for all—in which we employ the word "meaning" it can be defined thus: the meaning of a word is its use in the language." This is in opposition to traditional analytic philosophy which holds that the meaning is specified by external references and truth conditions.


Somebody should tell Philosophers about the Curry-Howard-Lambek isomorphism.

Because that's all there is to the Mathematical notion of "rigorous proof".

And the 'next step' in scaling up this process is the mission undertaken by the NuPRL project [1] well on our road towards internalising systems theory as the mode of scientific discourse [2]:

  Starting with the slogan "proofs-as-programs," we now talk about "theories-as-systems."
1. http://nuprl.org/Intro/intro.html

2. https://en.wikipedia.org/wiki/Systems_theory


What makes you think that philosophers haven't heard of it? Here's the Stanford Encyclopedia of Philosophy entry on it: https://plato.stanford.edu/entries/type-theory-intuitionisti...


It's not surprising, because Wittgenstein himself was in a sense dismissive of academic philosophy. He turned against his former self, of the Tractatus, which was highly regarded among so-called "analytic" philosophers. The controversy began almost immediately: Bertrand Russell, who had previously been Wittgenstein's biggest supporter, had nothing but scorn for the Philosophical Investigations.

Wittgenstein was a kind of anti-philosopher, as was Richard Rorty. Their goal, as I see it, was not to "solve" traditional philosophical problems as such, but rather to dissolve them. They believed that many philosophical problems were misunderstandings, projections of our human languages onto reality, false anthropomorphism. Rorty also started in academic philosophy and left the field later in his career, while generating similar controversy. If they're right, then it's unclear whether philosophy as it had traditionally been practiced has a proper place in society. Academic philosophers deem their own projects to be "foundational", but Wittgenstein was a threat to that way of thinking.


1. There are no foundations - it's turtles all the way down.

2. Recursion is the foundation.

3. This is a true contradiction.


You can't be a philosopher and posit "most philosophy is non-sense" at the same time. If language is the product of ephemeral transactions between subjective people on a need to communicate basis, then does it possess the objective rigor needed to accurately investigate the true essence of the world? If philosophy can only be expressed with language, where does that leave you? Setting aside Wittgenstein while you work on your philosophy may do the trick.

I've been listening to a lot of George Carlin recently. I feel much of his late best work is linguistic absurdism. If we are to take Carlin's assertion that most of us are dumb and society is glued together by bullshit, then so would be our language. If that is the case, then Carlin's stand up is the perfect example of taking language for what it truly is and applying objective rigor and logic to it (which he explicitly claims to be doing in many of his routines), only to reveal the true essence of the world. If anything, Carlin proved that reality is just as absurd as the language we use to describe it.


I'm not up on current PhD philosopher's tastes, and I'm biased since I'm a major fan of Wittgenstein, but, assuming you don't have a biased sample, I'd say this phenomenon is explainable through some of the Frankfurt School's theorizing on specialization, the professionalism of philosophy, and the general bureaucratic turn of society.

Personally, I like to view philosophy and academic philosophy as two distinct things. The former is represented best by the famous philosophers, many of whom would never make it past a peer review, e.g. Wittgenstein himself, Kierkegaard, Schopenhauer, Heidegger, Nietzsche, Deleuze, Guattari, Bataille, Adorno, even Foucault to an extent, etc.--I think the reason for this is that all of these famous, epoch shaping philosophers have a certain mysticism or poeticism about them--their work doesn't really hold up to the standards of academies, since these are institutions with very specific mechanisms and rules. All the great philosophers have a certain creativity and ingenuity to them that defies the confines of convention and reason.

Wittgenstein is in many respects a key player in shaping our modern though on logic, yet he was also an undeniable mystic who went so far as to say certain things escape representation and codification as formalized knowledge altogether, which is not amenable to the motives of academies--producing formalized knowledge that they can sell. I say this, again, as someone who entirely lacks context but who can imagine certain structural tendencies that would disfavor a philosopher like Wittgenstein.

Academic philosophy is, in my opinion, quite a different beast that's focused on solving very specialized and particular abstract problems deemed to be foundational, meta, or novel enough to escape analysis in the fields of application they'd otherwise belong to (the foundations of mathematics, of great concern to Wittgenstein and Turning as this post illustrates, is a good example of such a topic--it's too meta to be the concern of mathematics proper, too narrow to be the concern of a philosopher in the classical or "true" sense, who is supposed to concern herself with the broad problems of existence (like Wittgenstein points out, the living (assuming to philosophize still means to theorize on what it means to live a good life don't really need to concern themselves with such issues), so it falls to specialized academics).


It sounds to me that what you are labelling as 'Academic philosophy' (solving abstract problems) is very much the general process of meta-linguistic abstraction.

https://en.wikipedia.org/wiki/Metalinguistic_abstraction


Obviously just one anecdote, but my brother has a PhD in philosophy from Oxford and now teaches philosophy (albeit at a small college, not one of the major ones). Wittgenstein is one of his three big philosophy heroes (the others being Thomas Aquinas and a medieval Islamic scholar that I can't remember the name of).

Academic fashions are weird though.


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