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nLab > Latest Changes: type of propositions

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  1.  
    • CommentRowNumber1.
    • CommentAuthorMike Shulman
    • CommentTimeDec 1st 2016

    Is there any point to having both type of propositions and Prop? The analogous page-name Type is a redirect to type of types.

    • CommentRowNumber2.
    • CommentAuthorUrs
    • CommentTimeDec 1st 2016

    Not sure why this happened. I have merged the two entries now.

  3. added a section on the definition of types of propositions

    Anonymous

    diff, v9, current

  4. added rules for the type of all propositions

    Anonymous

    diff, v13, current

    • CommentRowNumber5.
    • CommentAuthorGuest
    • CommentTimeOct 17th 2022

    Should be possible to define the type of propositions via the universal property of the subobject classifier, something like

    ΓctxΓ⊢Ωtype\frac{\Gamma \; \mathrm{ctx}}{\Gamma \vdash \Omega \; \mathrm{type}} ΓctxΓ⊢true:Ω\frac{\Gamma \; \mathrm{ctx}}{\Gamma \vdash \mathrm{true}:\Omega} Γ⊢AtypeΓ⊢BtypeΓ⊢i:A↪BΓ⊢χ B:B→Ω\frac{\Gamma \vdash A \; \mathrm{type} \quad \Gamma \vdash B \; \mathrm{type} \quad \Gamma \vdash i:A \hookrightarrow B}{\Gamma \vdash \chi_B:B \to \Omega}

    et cetera

    • CommentRowNumber6.
    • CommentAuthorChristian Sattler
    • CommentTimeOct 17th 2022
    • (edited Oct 17th 2022)

    That’s effectively being done already when you say every proposition is classified by Ω\Omega. To derive your proposed rule, consider the proposition in context Γ.(b:B)\Gamma.(b : B) of preimages of bb under ii.

    Side note: we don’t currently have models of the type of all propositions (as currently defined, with a meta-equality El(A Ω)≡A\mathsf{El}(A_\Omega) \equiv A) in HoTT.

  7. added section on the type of all decidable propositions, or the type of booleans

    Anonymous

    diff, v17, current

  8. Added rules for the type of all propositions as a Russell universe.

    Anonymouse

    diff, v21, current

    • CommentRowNumber9.
    • CommentAuthorUrs
    • CommentTimeAug 2nd 2023

    Incidentally, I see that this entry is lacking any reference to subtype.

    • CommentRowNumber10.
    • CommentAuthorUrs
    • CommentTimeAug 2nd 2023

    added a sentence to the Idea-section which cross-links back to subtype.

    diff, v22, current

1 to 10 of 10

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