Propositional Equivalence, Tautologies, Contradictions, and Contingencies in Discrete Mathematics

In philosophy and logic, contingency is the status of propositions that are neither true under every possible valuation (i.e. tautologies) nor false under every possible valuation (i.e. contradictions). A contingent proposition is neither necessarily true nor necessarily false. Tautologies and Contradictions. Definition: A formula is said to be a Tautology if every truth assignment to its component statements results in the formula being true. A formula is said to be a Contradiction if every truth assignment to its component statements results in the formula being false.