apply IsDeduct.mp_ ((forall_ v P).imp_ P)
P : Formula
v : VarName
h1 : ¬isFreeIn v P
⊢ IsProof ((forall_ v P).iff_ P)
case a
P : Formula
v : VarName
h1 : ¬isFreeIn v P
⊢ IsDeduct ∅ (((forall_ v P).imp_ P).imp_ ((forall_ v P).iff_ P))

case a
P : Formula
v : VarName
h1 : ¬isFreeIn v P
⊢ IsDeduct ∅ ((forall_ v P).imp_ P)