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