Axioms of TruthLogik wrote: ↑Sat Mar 30, 2019 7:47 amYou keep bumping your head against the epistemic problem of criterion.PeteOlcott wrote: ↑Fri Mar 29, 2019 9:44 pm When an expression is shown to be unprovable by diagonalization this masks
over the key detail that it is only unprovable because it is ill-formed.
∀F ∈ Formal_Systems ∀x ∈ WFF(F) (True(F, x) ↔ (F ⊢ x))
Clearly that is an algorithm in your head which can determine which expression is "well formed" and which expression is "badly formed".
What is your classification rule?
https://en.wikipedia.org/wiki/Classification_rule
(1) ∀F∀x (True(F, x) ↔ (F ⊢ x))
(2) ∀F∀x (False(F, x) ↔ (F ⊢ ~x))
(3) ∀F∀x (~True(F, x) ↔ ~(F ⊢ x))
G ↔ ~(F ⊢ G) Means that G has the same Truth value as its own unprovability in F.
When the RHS ~(F ⊢ G) is true, by Truth axiom(3) we know that x is not true in F.
This contradicts the LHS being true, making the above expression false.