apply IsDeduct.mp_ ((Q.imp_ R).imp_ R)
case h1
Q R : Formula
⊢ IsDeduct (∅ ∪ {Q}) (R.not_.imp_ (Q.imp_ R).not_)
case h1.a
Q R : Formula
⊢ IsDeduct (∅ ∪ {Q}) (((Q.imp_ R).imp_ R).imp_ (R.not_.imp_ (Q.imp_ R).not_))

case h1.a
Q R : Formula
⊢ IsDeduct (∅ ∪ {Q}) ((Q.imp_ R).imp_ R)