x = y → true T → x = y → true ∀ (a : T), x = a → a = y ∀ (a : T), a = x → true T → T → x = y → true T → T → x = y → P y (∀ (x : T), P x ↔ Q x) → Q x Prop → (∀ (x : T), P x ↔ Q x) → Prop → Q x ∀ (a : Prop), (∀ (x : T), P x ↔ Q x) → a ∨ Q x (∀ (x : T), P x ↔ Q x) → Q x ∀ (a : T), T → (∀ (x : T), P x ↔ Q x) → Q a ∀ (a a_1 : T), a = a_1 → P a_1 ∀ (a a_1 a_2 : T), a = a_1 → a_1 = a_2 → P a_2 ∀ (a a_1 : T), a = a_1 → (∀ (w : T), P w ↔ Q w) → Q a_1