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

case h1.a.a.a.h2
P Q : Formula
v : VarName
h1 : ¬isFreeIn v Q
⊢ ∀ H ∈ {forall_ v (P.imp_ Q)}, ¬isFreeIn v H