∀ {α : Sort u_2} {β : Sort u_3} {s₁ : Setoid α} {s₂ : Setoid β} {motive : Quotient s₁ → Quotient s₂ → Sort u_1}
  [s : ∀ (a : α) (b : β), Subsingleton (motive ⟦a⟧ ⟦b⟧)] (q₂ : Quotient s₂) (a : α),
  Subsingleton (motive (Quot.mk (⇑s₁) a) q₂)