{X : SSet} →
  {A : X.Subcomplex} →
    {motive : A.Pairing → Sort u_1} →
      ((I II : Set A.N) →
          (inter : I ∩ II = ∅) →
            (union : I ∪ II = Set.univ) →
              (p : ↑II ≃ ↑I) → motive { I := I, II := II, inter := inter, union := union, p := p }) →
        (t : A.Pairing) → motive t