Question

Is law of excluded middle necessary in this proof?

score 674 · Answer 1 · 2026-03-26 15:17:08

674

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Is law of excluded middle necessary in this proof?

Published on 26 Mar 2026 - 15:17

score 149 · Answer 2 · 2026-03-25 03:01:43

149

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Is Goodstein's theorem equivalent to $\varepsilon_0$-induction over weak base theories (e.g. PRA)?

Published on 25 Mar 2026 - 3:01

score 166 · Answer 3 · 2026-02-23 08:43:05

166

Views

How to derive ${ A \vdash C }$ from ${A \lor B \vdash C}$ in the sequent calculus LK?

Published on 23 Feb 2026 - 8:43

score 259 · Answer 4 · 2026-02-23 08:40:54

259

Views

What is the definition of "a derivation of a sequent "?

Published on 23 Feb 2026 - 8:40

score 103 · Answer 5 · 2026-03-27 00:59:49

103

Views

Concrete examples of statements not provable in PRA + $\epsilon_0$-induction that are provable in PA?

Published on 27 Mar 2026 - 0:59

score 610 · Answer 6 · 2026-03-25 04:37:21

610

Views

How can you derive a formula without premises?

Published on 25 Mar 2026 - 4:37

score 227 · Answer 7 · 2026-03-26 19:17:09

227

Views

Interpreting $\textbf{PA} + \neg\text{Con}(\textbf{PA})$ in $\textbf{PA}$

Published on 26 Mar 2026 - 19:17

score 181 · Answer 8 · 2026-02-23 08:36:55

181

Views

Does an inference rule under natural deduction operate on sequents or formulas?

Published on 23 Feb 2026 - 8:36

score 124 · Answer 9 · 2026-03-25 06:06:23

124

Views

Isn't it problematic to cite the Gödel sentence as a proposition asserting 'This sentence is unprovable' since it isn't really on point?

Published on 25 Mar 2026 - 6:06

score 349 · Answer 10 · 2026-02-23 08:37:55

349

Views

Sequents: if-introduction and discharging assumptions

Published on 23 Feb 2026 - 8:37

score 504 · Answer 11 · 2026-03-25 20:39:45

504

Views

Meta proof-searching

Published on 25 Mar 2026 - 20:39

score 156 · Answer 12 · 2026-03-26 16:08:51

156

Views

Are theorems like subroutines for math?

Published on 26 Mar 2026 - 16:08

score 747 · Answer 13 · 2016-07-25 18:44:38

747

Views

Are there any proofs that only exist by induction?

Published on 25 Jul 2016 - 18:44

score 314 · Answer 14 · 2026-02-23 10:16:53

314

Views

Natural deduction sequents: $(\lnot)$ introduction and elimination

Published on 23 Feb 2026 - 10:16

score 515 · Answer 15 · 2026-03-29 06:02:30

515

Views

How can know if a proof technique can actually prove something? Specifically, induction

Published on 29 Mar 2026 - 6:02

List Question

Is law of excluded middle necessary in this proof?

Is Goodstein's theorem equivalent to $\varepsilon_0$-induction over weak base theories (e.g. PRA)?

How to derive ${ A \vdash C }$ from ${A \lor B \vdash C}$ in the sequent calculus LK?

What is the definition of "a derivation of a sequent "?

Concrete examples of statements not provable in PRA + $\epsilon_0$-induction that are provable in PA?

How can you derive a formula without premises?

Interpreting $\textbf{PA} + \neg\text{Con}(\textbf{PA})$ in $\textbf{PA}$

Does an inference rule under natural deduction operate on sequents or formulas?

Isn't it problematic to cite the Gödel sentence as a proposition asserting 'This sentence is unprovable' since it isn't really on point?

Sequents: if-introduction and discharging assumptions

Meta proof-searching

Are theorems like subroutines for math?

Are there any proofs that only exist by induction?

Natural deduction sequents: $(\lnot)$ introduction and elimination

How can know if a proof technique can actually prove something? Specifically, induction

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