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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.

69 votes
5 answers
9k views

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

According to Solomon Feferman, in his slide presentation "Three Problems for Mathematics", Hilbert wrote (in regards to Gödel's second incompleteness theorem): ...the end goal [is] to establish as …
1 vote
1 answer
360 views

How are Koepke's ordinal computability and E-recursion related?

In Koepke's paper, "Turing Computations On Ordinals", one has the following (well-known) result: A set $x$ is ordinal computable from a finite set of ordinal parameters if and only if it is an elemen …
5 votes
1 answer
475 views

Extensions of the Ackermann interpretation to nonstandard theories of arithmetic

In their paper, " On Interpretations of Arithmetic and Set Theory" (Notre Dame Journal of Formal Logic, Vol. 8, No. 4 (2007), pp. 497-510) in section 7, "Fragments of Arithmetic and Set Theory", Kaye …
0 votes
1 answer
878 views

Forcing the existence of a weakly inaccessible cardinal in some strong set theory

Does the fact that, assuming the consistency of $ZFC$, no proof that the consistency of "$ZFC$ implies the consistency of '$ZFC$ + There exists a weakly inaccessible cardinal'" can be formulated in $Z …
-4 votes
1 answer
596 views

What is an oracle, really? [closed]

Regarding oracles, might this be a reasonable description of their inner workings (this from Hartley Rogers, Jr.'s text, Theory of Recursive Functions and Effective Computability)? Why should I ask s …
0 votes
1 answer
307 views

Can finite sets be non-c.e. depending on how they are presented?

I ask the question because of the following statement found in Mark Burgin's paper, "Algorithmic complexity of recursive and inductive algorithms", Theoretical Computer Science 317 (2004) 31-60 (pg. 3 …
2 votes
2 answers
554 views

Are ITTM's necessary to compute Turing's "computable numbers" and what does that mean for or...

In his celebrated paper, "On Computable Numbers, With An Application To the Entscheidungsproblem", Turing defines a "computable number" as follows: The "computable" numbers may be described briefly a …
1 vote
2 answers
831 views

Is there an analogue of the Lost Melody Theorem in ordinary recursion theory and if not, why...

In their arXiv preprint, "Infinite Time Turing Machines" (arXiv:math/9808093v1 [math.LO] 21 Aug 1998) Hamkins and Lewis state the Lost Melody Theorem for ITTM's as follows: Lost Melody Theorem 4.9 [p …
2 votes
1 answer
452 views

Is the statement "All numbers are counting numbers" independent of $PA$?

In his paper, "Completed versus Incomplete Infinity in Arithmetic" (which can be found here), the late Edward Nelson defines the notion of 'counting number' as follows: 0 is a counting number if $y$ …
0 votes
3 answers
1k views

Regarding Gentzen's note regarding 'Godel-points' (i.e., "Where is the Godel-point hiding?")

Consider the following note written by Gerhard Gentzen in early 1932, on the onset of his work on a consistency proof for arithmetic: The axioms of arithmetic are obviously correct, and the princi …
6 votes
3 answers
3k views

The Lucas argument vs the theorem-provers -- who wins and why?

In his paper, "Minds, Machines and Gödel", J.R. Lucas writes the following: Gödel's theorem [First Incompleteness Theorem, that is—my comment] must apply to cybernetic machines, because it is of t …
-4 votes
2 answers
454 views

Is the notion of measurable cardinal definable from the perspective of set-theoretical poten...

Consider the definition of measurable cardinal (this definition was found in Neil Barton's paper, "Large cardinals and the iterative conception of set"): Definition 8. A cardinal $\kappa$ is measura …
2 votes
0 answers
323 views

The universe and multiverse views of set theory from the perspective of $ZFC^2$

(Note: the 'Second-order $ZFC$' ($ZFC^2$) I am talking about is the theory [in the second order language of set theory consisting of a single non-logical symbol $\in$ ] consisting of the axioms Exte …
5 votes
0 answers
940 views

Why are real-valued measurable cardinals never explicitly mentioned in Gödel's "What is Cant...

It is a matter of mathematical folklore that Gödel "entertained the idea of so called stronger axioms of infinity deciding $CH$...." (this quote from Radek Honzik's paper, "Large cardinals and the Co …
-4 votes
2 answers
870 views

Can only the constructible sets be proven to exist in $ZF$ without benefit of extra assumpti... [closed]

I am interested in asking the following question: What sets can be proven to exist in $ZF$ without the benefit of extra assumptions? (Thanks to Toshiyasu Arai for inspiring me to ask this variation o …

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