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  2. List of rules of inference - Wikipedia

    en.wikipedia.org/wiki/List_of_rules_of_inference

    Examples: The column-14 operator (OR), shows Addition rule : when p =T (the hypothesis selects the first two lines of the table), we see (at column-14) that p ∨ q =T. We can see also that, with the same premise, another conclusions are valid: columns 12, 14 and 15 are T.

  3. If and only if - Wikipedia

    en.wikipedia.org/wiki/If_and_only_if

    The biconditional is true in two cases, where either both statements are true or both are false. The connective is biconditional (a statement of material equivalence), [2] and can be likened to the standard material conditional ("only if", equal to "if ... then") combined with its reverse ("if"); hence the name. The result is that the truth of ...

  4. Propositional calculus - Wikipedia

    en.wikipedia.org/wiki/Propositional_calculus

    [35] [36] In English, these connectives are expressed by the words "and" (conjunction), "or" (disjunction), "not" , "if" (material conditional), and "if and only if" (biconditional). [1] [13] Examples of such compound sentences might include: Wikipedia is a free online encyclopedia that anyone can edit, and millions already have. (conjunction)

  5. Material implication (rule of inference) - Wikipedia

    en.wikipedia.org/wiki/Material_implication_(rule...

    In propositional logic, material implication [1] [2] is a valid rule of replacement that allows a conditional statement to be replaced by a disjunction in which the antecedent is negated. The rule states that P implies Q is logically equivalent to not-or and that either form can replace the other in logical proofs.

  6. De Morgan's laws - Wikipedia

    en.wikipedia.org/wiki/De_Morgan's_laws

    De Morgan's laws represented with Venn diagrams.In each case, the resultant set is the set of all points in any shade of blue. In propositional logic and Boolean algebra, De Morgan's laws, [1] [2] [3] also known as De Morgan's theorem, [4] are a pair of transformation rules that are both valid rules of inference.

  7. Logical biconditional - Wikipedia

    en.wikipedia.org/wiki/Logical_biconditional

    Venn diagram of (true part in red) In logic and mathematics, the logical biconditional, also known as material biconditional or equivalence or bidirectional implication or biimplication or bientailment, is the logical connective used to conjoin two statements and to form the statement "if and only if" (often abbreviated as "iff " [1]), where is known as the antecedent, and the consequent.

  8. Logical connective - Wikipedia

    en.wikipedia.org/wiki/Logical_connective

    Conjunction Both A and B conjunct A and B are conjoined Disjunction Either A or B, or both disjunct A and B are disjoined Negation It is not the case that A negatum/negand A is negated Conditional If A, then B antecedent, consequent B is implied by A Biconditional A if, and only if, B equivalents A and B are equivalent

  9. Logical conjunction - Wikipedia

    en.wikipedia.org/wiki/Logical_conjunction

    Here is an example of an argument that fits the form conjunction introduction: Bob likes apples. Bob likes oranges. Therefore, Bob likes apples and Bob likes oranges. Conjunction elimination is another classically valid, simple argument form. Intuitively, it permits the inference from any conjunction of either element of that conjunction.