Encyclopedia Mathematics Mathematics Godel Theorems Structural From Rs

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Mathematics Godel Theorems Structural From Rs

Gödel's incompleteness theorems, Tarski's undefinability, Church's undecidability, and Turing's halting problem form a set of exactly five, and a machine-checked library records that count.

The five limitative results as a counting fact

The classical limitative results of mathematical logic are the theorems that set hard boundaries on what formal systems can prove, define, or decide. Gödel's first incompleteness theorem (1931) shows that any consistent system strong enough for arithmetic contains statements it can neither prove nor refute. His second (1931) shows such a system cannot prove its own consistency. Tarski's undefinability of truth (1933) shows a system cannot define its own truth predicate. Church's undecidability (1936) shows no algorithm can decide all mathematical statements. Turing's halting problem (1936) shows no algorithm can determine whether a given program will finish.

These five results share a structural shape: each is a limitative statement about what a formal system or algorithm cannot do. The module recognition, a discrete record of events, treats them as labels on a five-element type. The machine-checked library of formal theorems proves the count: Fintype.card LimitativeResult = 5. This is a bare counting fact, the kind of structural reference used to plug into dimension-counting bridges elsewhere in the framework.

What the module does not do is claim that Recognition Science evades any of these five results. None of the five constructors carries a proof that the corresponding theorem fails to apply to the framework. The names are labels attached to constructors of a five-element inductive type; they have the same logical content as the labels on a Fin 5. The module is a reference card, not a escape hatch.

In Recognition Science, the framework models its own arithmetic as inheriting Gödel's first incompleteness theorem just as Peano arithmetic does. The honest assessment of how Gödel I and Tarski's undefinability interact with the framework is a separate categorical argument about target classes, documented in a paper on the closure assessment. The module itself stays at the level of enumeration: five results, one type, one count.

THEOREM LimitativeResult · IndisputableMonolith/Mathematics/GodelTheoremsStructuralFromRS.lean
inductive LimitativeResult where
  | godelFirst
  | godelSecond
  | tarskiUndefinability
  | churchUndecidability
  | turingHalting
  deriving DecidableEq, Repr, BEq, Fintype
THEOREM limitativeResult_count · IndisputableMonolith/Mathematics/GodelTheoremsStructuralFromRS.lean
theorem limitativeResult_count :
    Fintype.card LimitativeResult = 5 := by decide
THEOREM LimitativeResult · IndisputableMonolith/Mathematics/GodelTheoremsStructuralFromRS.lean
inductive LimitativeResult where
  | godelFirst
  | godelSecond
  | tarskiUndefinability
  | churchUndecidability
  | turingHalting
  deriving DecidableEq, Repr, BEq, Fintype

What this page does not claim

Recognition Science evades any of the five limitative results. The module proves Gödel's theorems themselves; it only counts them. The five results are logically equivalent to each other.

Verify this page

Every tagged claim above names its theorem. To check one yourself rather than trust this page, elaborate the source module with Lean 4 and audit its axiom basis:

$ lake env lean IndisputableMonolith/Mathematics/GodelTheoremsStructuralFromRS.lean
expected axiom basis: [propext, Classical.choice, Quot.sound] (the Lean kernel's standard three; no RS-specific axioms)

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