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Philosophical aspects of logic and set theory; truth status of mathematical axioms; Philosophy of Mathematics; philosophical aspects of mathematics in general; relation of mathematics to philosophy; etc. Consider also posting at http://philosophy.stackexchange.com/, where philosophy-of-mathematics is one of the most popular tags.

21 votes
Accepted

Question arising from Voevodsky's talk on inconsistency

Let $S$ be a first order definable Martin-Löf random set such as Chaitin's $\Omega$. If Peano Arithmetic, or ZFC, or any other theory with a computable set of axioms, proves infinitely many facts of t …
Bjørn Kjos-Hanssen's user avatar
4 votes

Gödel's ontological proof & Benzmüller's work

I know Benzmüller's work from a slightly different context, formalizing other interesting systems of modal logic. Hadn't heard of this specific project, but it seems very admirable. Formalization of …
Bjørn Kjos-Hanssen's user avatar
13 votes

Interesting meta-meta-mathematical theorems?

You could let $\alpha_0$ be the statement Con(ZFC), and $\alpha_{n+1}$ be ZFC $\not\vdash\alpha_n$, and at limit ordinals $\alpha_\lambda$ is $(\forall \beta<\lambda)($ZFC $\not\vdash \alpha_\beta)$. …
Bjørn Kjos-Hanssen's user avatar
18 votes

Why is this new result such a big deal?

They show that $\DeclareMathOperator{\WKL}{WKL}\DeclareMathOperator{\RT}{RT}\DeclareMathOperator{\RCA}{RCA} \RT^2_2$ is $\Pi^0_3$-conservative over $\RCA_0$. Thus, there is no way that $\RT^2_2$ can b …
Bjørn Kjos-Hanssen's user avatar
4 votes

Can we define an "empirically generic" real number?

It sounds like you are talking about what in computability theory and set theory are known as Cohen generic reals (the lowest level of which in computability theory is 1-generic, then 2-generic and so …
Bjørn Kjos-Hanssen's user avatar
5 votes

What was Hilbert's view of Gödel's Incompleteness Theorems?

Here's the Logicomix account of Hilbert's reaction. Perhaps a reference to Hilbert's Hotel?
Bjørn Kjos-Hanssen's user avatar