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

case a
P : Formula
u v : VarName
⊢ IsDeduct ∅ ((forall_ u (forall_ v P)).imp_ (forall_ v (forall_ u P)))