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1. • CommentRowNumber1.
   • CommentAuthornLab edit announcer
   • CommentTimeAug 21st 2019
   • PermaLink
   Author: nLab edit announcer
   Format: MarkdownItexLink to S5 and S4(m) Ammar Husain <a href="https://ncatlab.org/nlab/revision/diff/the+logic+S5%28m%29/6">diff</a>, <a href="https://ncatlab.org/nlab/revision/the+logic+S5%28m%29/6">v6</a>, <a href="https://ncatlab.org/nlab/show/the+logic+S5%28m%29">current</a>

   Link to S5 and S4(m)

   Ammar Husain

   diff, v6, current

2. • CommentRowNumber2.
   • CommentAuthornLab edit announcer
   • CommentTimeJul 21st 2022
   • PermaLink
   Author: nLab edit announcer
   Format: MarkdownItex[[Tim Porter]] wrote the following question on a now-removed query box: +-- {: .query} [[Tim Porter]] It would be good to have some discussion on this axiom. (Donald Rumsfeld's known unknowns has been worked to death, (although sometimes quite well done as [here](http://wn.com/modal_logic)), so please... something worth saying :-)). This might stray over to a new entry as I would hope to see what there is to say especially looking to models of 'why' an agent 'knows' something. My query is whether that aspect has been explored and if so where. My feeling is that in S5 (and elsewhere) the reasons may give a groupoid-like structure (see below about the Kripke semantics) for the geometric semantics. =-- Anonymous <a href="https://ncatlab.org/nlab/revision/diff/the+logic+S5%28m%29/7">diff</a>, <a href="https://ncatlab.org/nlab/revision/the+logic+S5%28m%29/7">v7</a>, <a href="https://ncatlab.org/nlab/show/the+logic+S5%28m%29">current</a>

   Tim Porter wrote the following question on a now-removed query box:

   +– {: .query} Tim Porter It would be good to have some discussion on this axiom. (Donald Rumsfeld’s known unknowns has been worked to death, (although sometimes quite well done as here), so please… something worth saying :-)). This might stray over to a new entry as I would hope to see what there is to say especially looking to models of ’why’ an agent ’knows’ something. My query is whether that aspect has been explored and if so where. My feeling is that in S5 (and elsewhere) the reasons may give a groupoid-like structure (see below about the Kripke semantics) for the geometric semantics. =–

   Anonymous

   diff, v7, current

3. • CommentRowNumber3.
   • CommentAuthorUrs
   • CommentTimeJul 16th 2023
   • (edited Jul 16th 2023)
   • PermaLink
   Author: Urs
   Format: MarkdownItexhappened again onto this entry and tried to fix it up a little more: * replaced the Idea-section with a more informative sentence * finally fixed the typesetting error (a spurious dollar sign) in the "proof" which was causing followup misrenderings * changed the page name from "the logic S5(m)" to a more canonical title The entry is still not in good shape, but I leave it as is for the moment. <a href="https://ncatlab.org/nlab/revision/diff/S5%28m%29+modal+logic/8">diff</a>, <a href="https://ncatlab.org/nlab/revision/S5%28m%29+modal+logic/8">v8</a>, <a href="https://ncatlab.org/nlab/show/S5%28m%29+modal+logic">current</a>

   happened again onto this entry and tried to fix it up a little more:

   • replaced the Idea-section with a more informative sentence

   • finally fixed the typesetting error (a spurious dollar sign) in the “proof” which was causing followup misrenderings

   • changed the page name from “the logic S5(m)” to a more canonical title

   The entry is still not in good shape, but I leave it as is for the moment.

   diff, v8, current