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@FormalizedFormalLogic

Formalized Formal Logic

Formalize Formal Logic in Lean4

Formalized Formal Logic

Formalize formal logic (mathematical logic) in Lean Theorem Prover.

Our main repository is Foundation. See Catalogue (In progress) and Doc for more results and details.

  • Propositional Logic
    • Completeness for Classical Logic
    • Kripke Semantics for Intuitionistic Logics and Superintuitionistic Logics.
  • Intuitionistic and Classical First-Order Logic
    • Arithmetic and Set Theory
    • Completeness Theorem
    • Cut-elimination of First-Order Sequent Calculus (Gentzen's Hauptsatz)
    • Gödel's First and Second Incompleteness Theorems
    • Solovay's Arithmetical Completeness Theorem
  • Basic Modal Logic (with modal operators $\Box, \Diamond$)
    • Kripke Semantics and Completeness
    • Modal Cube
    • Modal Companion
    • Provability Logic
  • Interpretability Logic

Developers

  • Palalansoukî (Shogo Saito, @iehality, ✉️:[email protected])
    • Overall design and maintenance.
    • First-order logic.
    • Intuitionistic first-order logic.
    • Proof automation.
    • Provability logic.
  • SnO2WMaN (Mashu Noguchi, @SnO2WMaN, ✉️:[email protected])
    • Modal logic.
    • Propositional logic (including intermediate logic).
    • Provability logic.
    • Interpretability Logic.
    • Miscellaneous repository maintenance (e.g. GitHub Actions)

Financial Supports

Any financial supports would be grateful for us. If you found this project valuable, to sustain our OSS development, please consider support us.

Open Collective

Open Collective

We would like to thanks the following backers.

Open Collective Backers

Previous Backers

Individuals and organizations that have supported us in the past.

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  1. Foundation Foundation Public

    Formalization of Mathematical Logic

    Lean 195 11

  2. Catalogue Catalogue Public

    Catalogue of FFL

    Lean

Repositories

Showing 10 of 10 repositories
  • Foundation Public

    Formalization of Mathematical Logic

    FormalizedFormalLogic/Foundation’s past year of commit activity
    Lean 195 Apache-2.0 11 45 22 Updated Jan 8, 2026
  • Catalogue Public

    Catalogue of FFL

    FormalizedFormalLogic/Catalogue’s past year of commit activity
    Lean 0 Apache-2.0 0 6 2 Updated Jan 8, 2026
  • .github Public

    Formalized Formal Logic

    FormalizedFormalLogic/.github’s past year of commit activity
    0 0 0 0 Updated Jan 8, 2026
  • GodExistence Public

    Gödel's Ontological Argument

    FormalizedFormalLogic/GodExistence’s past year of commit activity
    Lean 1 0 0 0 Updated Jan 1, 2026
  • Book Public archive

    Summary

    FormalizedFormalLogic/Book’s past year of commit activity
    Markdown 5 CC-BY-4.0 1 2 2 Updated Jul 1, 2025
  • Incompleteness Public archive

    Formalize Incompleness Theorem Related Results

    FormalizedFormalLogic/Incompleteness’s past year of commit activity
    Lean 8 Apache-2.0 0 0 1 Updated Mar 8, 2025
  • Arithmetization Public archive

    Formalization of Arithmetization of Mathematics/Metamathematics

    FormalizedFormalLogic/Arithmetization’s past year of commit activity
    Lean 13 Apache-2.0 2 0 0 Updated Mar 8, 2025
  • LogicsKite Public archive

    Kites of Logics

    FormalizedFormalLogic/LogicsKite’s past year of commit activity
    Lean 1 0 1 0 Updated Mar 8, 2025
  • Summary Public archive

    Documentation of this project

    FormalizedFormalLogic/Summary’s past year of commit activity
    Lean 0 0 10 0 Updated Feb 2, 2025
  • LabelledSystem Public

    Label-based Caliculi for Modal Logic

    FormalizedFormalLogic/LabelledSystem’s past year of commit activity
    Lean 1 Apache-2.0 0 0 0 Updated Dec 19, 2024