{α : Type u_1} →
  {r : SetRel α α} →
    (motive : RelSeries r → Sort u_3) →
      ((x : α) → motive (RelSeries.singleton r x)) →
        ((p : RelSeries r) → (x : α) → (hx : (p.last, x) ∈ r) → motive p → motive (p.snoc x hx)) →
          (p : RelSeries r) → motive p