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  2. Tautology (logic) - Wikipedia

    en.wikipedia.org/wiki/Tautology_(logic)

    The method of truth tables illustrated above is provably correct – the truth table for a tautology will end in a column with only T, while the truth table for a sentence that is not a tautology will contain a row whose final column is F, and the valuation corresponding to that row is a valuation that does not satisfy the sentence being tested.

  3. Truth table - Wikipedia

    en.wikipedia.org/wiki/Truth_table

    t. e. A truth table is a mathematical table used in logic —specifically in connection with Boolean algebra, Boolean functions, and propositional calculus —which sets out the functional values of logical expressions on each of their functional arguments, that is, for each combination of values taken by their logical variables. [ 1 ]

  4. Tautological consequence - Wikipedia

    en.wikipedia.org/wiki/Tautological_consequence

    Tautological consequence can also be defined as ∧ ∧ ... ∧ → is a substitution instance of a tautology, with the same effect. [2]It follows from the definition that if a proposition p is a contradiction then p tautologically implies every proposition, because there is no truth valuation that causes p to be true and so the definition of tautological implication is trivially satisfied.

  5. Law of thought - Wikipedia

    en.wikipedia.org/wiki/Law_of_thought

    "The principles of Contradiction and Excluded ... 1.6 is a tautology (true no matter what the truth-value ... of Principia not only in the truth table development but ...

  6. Tautology (rule of inference) - Wikipedia

    en.wikipedia.org/wiki/Tautology_(rule_of_inference)

    In propositional logic, tautology is either of two commonly used rules of replacement. [1][2][3] The rules are used to eliminate redundancy in disjunctions and conjunctions when they occur in logical proofs. They are: The principle of idempotency of disjunction: and the principle of idempotency of conjunction: Where " " is a metalogical symbol ...

  7. Logical truth - Wikipedia

    en.wikipedia.org/wiki/Logical_truth

    In other words, a logical truth is a statement which is not only true, but one which is true under all interpretations of its logical components (other than its logical constants). Thus, logical truths such as "if p, then p" can be considered tautologies. Logical truths are thought to be the simplest case of statements which are analytically ...

  8. De Morgan's laws - Wikipedia

    en.wikipedia.org/wiki/De_Morgan's_laws

    and expressed as truth-functional tautologies or theorems of propositional logic: (), ().where and are propositions expressed in some formal system.. The generalized De Morgan's laws provide an equivalence for negating a conjunction or disjunction involving multiple terms.

  9. Method of analytic tableaux - Wikipedia

    en.wikipedia.org/wiki/Method_of_analytic_tableaux

    A graphical representation of a partially built propositional tableau. In proof theory, the semantic tableau [1] (/ t æ ˈ b l oʊ, ˈ t æ b l oʊ /; plural: tableaux), also called an analytic tableau, [2] truth tree, [1] or simply tree, [2] is a decision procedure for sentential and related logics, and a proof procedure for formulae of first-order logic. [1]