- Certainly true: not false
  - Certainly true: {1, 2} =!= {2, 1}
    - Left side:  {1, 2}
    - Right side: {1, 2}
  - Certainly true: ∃a, b. (a /\ b) =!= (a \/ b)
    Found example:
      a = false
      b = false
  - Certainly false: ∀a, b. (a /\ b) =!= (a \/ b)
    Found counterexample:
      a = false
      b = true