The extensional set of boolean truth values.
(<=> (Boolean-Value ?True-Or-False) (Or (= ?True-Or-False True) (= ?True-Or-False False)))
(Or (= ?True-Or-False True) (= ?True-Or-False False))
(<=> (Boolean-Value ?True-Or-False) (Or (= ?True-Or-False True) (= ?True-Or-False False)))