try first
| apply verum!;
| apply imply₁!;
| apply imply₂!;
| apply conj₁!;
| apply conj₂!;
| apply conj₃!;
| apply disj₁!;
| apply disj₂!;
| apply disj₃!;
| apply dne!;
case hDne
α : Type u_1
inst✝² : DecidableEq α
𝓓₁ 𝓓₂ : DeductionParameter α
inst✝¹ : 𝓓₁.Normal
inst✝ : 𝓓₂.Normal
hMaxm : ∀ {p : Formula α}, p ∈ Ax(𝓓₁) → 𝓓₂ ⊢! p
p p✝ : Formula α
⊢ 𝓓₂ ⊢! ~~p✝ ⟶ p✝
no goals