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