Godel would like to talk to you about his “Incompleteness Theorem”
They are not claiming all possible theorems are formalizable. They are claiming to try to formalize all already proven theorems in the mathematics canon.
To the extent the theorems in question are impossible to formalize this means the original proof must be in error.
Theorems by definition must be formalizable. A theorem is not simply a true proposition, it's a provable proposition and a proof is necessarily a formal/syntactic property of a proposition.
That said, I agree with the sentiment that dismissing the entire article on the basis of the incompleteness theorems is shallow and the article is not about formalizing "all" of mathematics in the strict sense. It's mostly about introducing formal tools to the everyday mathematics.
Yes that's fair. To be accurate the formal definition of a theorem entails that provability. I was being too loose in essentially using "theorem" to refer to any proposition.
A bit like a multiverse of mathematics.
Perhaps you'd like to explain how you think the Incompleteness theorems affect this project?
That makes it sound like all possible mathematics past and future in all conceivable worlds. And we already know there are undecidable or unprovable statements, higher-order logics that cannot be fully formalized, concepts about axioms themselves that cannot be axiomatized, etc.
So it cannot mean "all of mathematics", strictly speaking. Just the areas in existing mathematics that have (or can have) formal proofs.
Feels like every time formalization is mentioned on hn somebody mentions incompleteness as though mathematicians in the field have never heard of it. It’s kind of annoying at this point. It’s like if every time we talked about a computer algorithm someone popped in to say “Have you heard of ‘On Computable Numbers’? Alan Turing would like a word.”
People in the field know about these things probably better than we do. They are aware of the consequences of completeness/incompleteness, decidability, computability etc. In fact Goedel’s completness and 2 incompleteness theorems have been formalized in lean as part of mathlib4 https://formalizedformallogic.org/Book/first_order/goedel1.h...
『Leanを用いたGödelの第一・第二不完全性定理の形式化』
..Oh I found a newer (more complete :) version of the proofs under the same domain.
https://formalizedformallogic.org/Catalogue/Arithmetic/G___d...
Looks like the /Book route is from an archived repo (https://github.com/FormalizedFormalLogic/book) and the content was moved to the Foundation's Catalogue. https://formalizedformallogic.org/Catalogue/
From the posted link, How to Formalize All of Mathematics, in the introduction:
> vision of how we can all work toward a world in which all, or almost all, mathematical definitions, theorems, and proofs are equipped with a formal representation
That "or almost all" feels like a wink to acknowledge the commonly misunderstood limitations of formal logic and systems. Your frustration is understandable, someone even wrote a whole book about it.
Franzén, Torkel. Gödel's Theorem: An Incomplete Guide to Its Use and Abuse
As the silliest example of this: the Calculus of Inductive Constructions (the core calculus implemented in Lean) has a published proof of its soundness (that you cannot derive False in it). That proof can (probably, thanks to Gödel) not be formalized in Lean or any formal system of axioms weaker than Lean.
If what you were trying to do was define what it means for something to be a correct proof, then you must equally admit that there can't be a correct proof of the fact that Lean can't prove False. And if you find that world a happy world to live in while we delegate all concerns about truth to Lean, then I have an infinite hierarchy of monotonically growing bridges to sell you.
Any proof which is correct can be formalized. That is what is means for a proof to be correct.
I’m not sure why you are restricting the scope of our discussion to what _Lean_ can(not) formalize. Even if we do choose to do that for some reason, Lean is not a formal system of fixed axioms; it supports optional additional axioms.
https://ia801804.us.archive.org/35/items/A-Z_Library_G-K_Jos... (PDF)
The ability to conjure math is practically as endless as time
At some point the outcome is just generation of new visual art in the form of syntax
We can't physically observe the past or future so we can only theorize and simulate; IMO that's the physical phenomena that belies Incompleteness Theorem; from Earth in the relative year of 2026 my view of the universe is fundamentally incomplete. As such all language describing too far either is incomplete always.
It makes any kind of longtermism, religious or agnostic framework espoused by kids of rich academics, empty. We all gonna stick around 10 more generations just to make sure?
Whole lot of educated people are just peddling euphemism for religious conviction they steeped in as kids but hid behind atheist semantics like "Intelligent Design."