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

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