A sequence of [[Proposition]]s and [[Logical Operations]] that is always true, regardless of whether the Propositions were true or not. Example: - $\neg A \lor A$ is always true - $2B:$ This object is a blackberry - $\neg 2B:$ This object is not a blackberry - $2B \lor \neg 2B$ (In this case... that is not the question... because it is a tautology)