∀ {α : Type u_1} [inst : Preorder α] {s : Set α} {m : α} (a : α)
  (motive : (∃ z ∈ s, (fun x1 x2 => x1 ≤ x2) m z ∧ (fun x1 x2 => x1 ≤ x2) a z) → Prop)
  (x : ∃ z ∈ s, (fun x1 x2 => x1 ≤ x2) m z ∧ (fun x1 x2 => x1 ≤ x2) a z),
  (∀ (x : α) (xs : x ∈ s) (xm : m ≤ x) (xa : a ≤ x), motive ⋯) → motive x