clear pI_prop
case h.right.left
φ ψ : Formula
hyp : φ⊨ψ
X : TNode := ([φ], [~ψ], none)
ctX : ClosedTableau ([], []) X
θ : Formula
pI_prop : voc θ ⊆ jvoc X ∧ ¬satisfiable ((~θ) :: X.left) ∧ ¬satisfiable (θ :: X.right)
this : ¬satisfiable ((~θ) :: X.left)
⊢ φ⊨θ
case h.right.left
φ ψ : Formula
hyp : φ⊨ψ
X : TNode := ([φ], [~ψ], none)
ctX : ClosedTableau ([], []) X
θ : Formula
this : ¬satisfiable ((~θ) :: X.left)
⊢ φ⊨θ