fact: Definition fun_rel' phi := ∀ ∀ ∀ phi[$2 .: $1 .: Nat.add 3 >> var] → phi[$2 .: $0 .: Nat.add 3 >> var] → $1 ≡' $0.
imports: Undecidability.FOL.Utils.FullSyntax Undecidability.FOL.Sets.Signatures Undecidability.FOL.Sets.ZF List