In a deductive system with conjunction and disjunction connectives and , respectively, a unary connective that is both a De Morgan negation (i.e., is involutive and satisfies De Morgan’s laws) and obeys the principle of explosion.
It can be inferred from this that orthonegations also satisfy the law of excluded middle:
Orthonegation arises when negation is given truth conditions in terms of incompatibility (or orthogonality) between states, so that is true at a state precisely when for every state at which is true, and are incompatible, i.e., .