Search Results
| Search type | Search syntax |
|---|---|
| Tags | [tag] |
| Exact | "words here" |
| Author |
user:1234 user:me (yours) |
| Score |
score:3 (3+) score:0 (none) |
| Answers |
answers:3 (3+) answers:0 (none) isaccepted:yes hasaccepted:no inquestion:1234 |
| Views | views:250 |
| Code | code:"if (foo != bar)" |
| Sections |
title:apples body:"apples oranges" |
| URL | url:"*.example.com" |
| Saves | in:saves |
| Status |
closed:yes duplicate:no migrated:no wiki:no |
| Types |
is:question is:answer |
| Exclude |
-[tag] -apples |
| For more details on advanced search visit our help page | |
Results tagged with lo.logic
Search options not deleted
user 57888
first-order and higher-order logic, model theory, set theory, proof theory, computability theory, formal languages, definability, interplay of syntax and semantics, constructive logic, intuitionism, philosophical logic, modal logic, completeness, Gödel incompleteness, decidability, undecidability, theories of truth, truth revision, consistency.
14
votes
Accepted
How can any theory prove well-foundedness of ordinals above $\omega_1^{\text{CK}}$?
Just slightly expanding the comment of Emil Jeřábek: on one hand, in ZFC we can define some objects we call ordinals and prove transfinite induction of each of them. This is not what we mean by the or …
- 1,229
14
votes
Why is an internal proof of consistency satisfactory for some systems?
The original context of Gödel's Theorem was slightly different. Famously, Hilbert had asked for a purely combinatorial proof of consistency for strong set theories. Notice that this seems like a very …
- 1,229
7
votes
End Extension models of $I\Delta_0$
Actually it's not even true that any model of $I\Delta_0$ admits an end extension to a model of this theory.
Even worse, we don't know whether such an end extension exists even if you allow the small …
- 1,229
7
votes
When is it okay to intersect infinite families of proper classes?
Here is an example of a family of classes of rings which you couldn't intersect: The class $A_n$ consists of all rings of power greater than n and the rings of cardinality $k≤n$ such that $ϕ_k$, where …
- 1,229