Proposition 1.2.5.
Bool = {⊤, ⊥}
Proof.
  • Let b ∈ Bool. Then b ∈ {⊤, ⊥}:
    We show that b = ⊤ or b = ⊥:
    Assume b ≠ ⊥. Then b = ⊤:
    We have b is true by definition.
  • Trivial.