apply IsDeduct.axiom_
case h1.a.a.a
P Q : Formula
v : VarName
h1 : ¬isFreeIn v Q
⊢ IsDeduct {forall_ v (P.imp_ Q)} ((forall_ v (Q.not_.imp_ P.not_)).imp_ ((forall_ v Q.not_).imp_ (forall_ v P.not_)))
case h1.a.a.a.a
P Q : Formula
v : VarName
h1 : ¬isFreeIn v Q
⊢ IsAxiom ((forall_ v (Q.not_.imp_ P.not_)).imp_ ((forall_ v Q.not_).imp_ (forall_ v P.not_)))