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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. Disjunction elimination - Wikipedia

    en.wikipedia.org/wiki/Disjunction_elimination

    In propositional logic, disjunction elimination [1] [2] (sometimes named proof by cases, case analysis, or or elimination) is the valid argument form and rule of inference that allows one to eliminate a disjunctive statement from a logical proof.

  4. Rule of inference - Wikipedia

    en.wikipedia.org/wiki/Rule_of_inference

    For example, the rule of inference called modus ponens takes two premises, one in the form "If p then q" and another in the form "p", and returns the conclusion "q". The rule is valid with respect to the semantics of classical logic (as well as the semantics of many other non-classical logics ), in the sense that if the premises are true (under ...

  5. Double negation - Wikipedia

    en.wikipedia.org/wiki/Double_negation

    The rule allows one to introduce or eliminate a negation from a formal proof. The rule is based on the equivalence of, for example, It is false that it is not raining. and It is raining. The double negation introduction rule is: P P. and the double negation elimination rule is:

  6. Modus ponens - Wikipedia

    en.wikipedia.org/wiki/Modus_ponens

    In propositional logic, modus ponens (/ ˈ m oʊ d ə s ˈ p oʊ n ɛ n z /; MP), also known as modus ponendo ponens (from Latin 'mode that by affirming affirms'), [1] implication elimination, or affirming the antecedent, [2] is a deductive argument form and rule of inference. [3] It can be summarized as "P implies Q. P is true. Therefore, Q ...

  7. Natural deduction - Wikipedia

    en.wikipedia.org/wiki/Natural_deduction

    There are ten primitive rules of proof, which are the rule assumption, plus four pairs of introduction and elimination rules for the binary connectives, and the rule reductio ad adbsurdum. [17] Disjunctive Syllogism can be used as an easier alternative to the proper ∨-elimination, [ 17 ] and MTT and DN are commonly given rules, [ 22 ...

  8. Conjunction elimination - Wikipedia

    en.wikipedia.org/wiki/Conjunction_elimination

    The rule makes it possible to shorten longer proofs by deriving one of the conjuncts of a conjunction on a line by itself. An example in English: It's raining and it's pouring. Therefore it's raining. The rule consists of two separate sub-rules, which can be expressed in formal language as: and

  9. Existential instantiation - Wikipedia

    en.wikipedia.org/wiki/Existential_instantiation

    The rule has the restrictions that the constant c introduced by the rule must be a new term that has not occurred earlier in the proof, and it also must not occur in the conclusion of the proof. It is also necessary that every instance of x {\displaystyle x} which is bound to ∃ x {\displaystyle \exists x} must be uniformly replaced by c .