Practice question · Sort into groups
Sort each rule by whether it introduces or eliminates a connective.
Groups: Introduction rule · Elimination rule
- From a conditional and its antecedent, infer the consequent
- From P, infer the disjunction of P with anything
- From P and Q, infer their conjunction
- From a conjunction, infer one conjunct
Hints
- Ask whether the connective appears in the conclusion or in the premise.
- If the rule builds a sentence with that connective, it introduces it.
Show the answer
Introduction rule: From P and Q, infer their conjunction, From P, infer the disjunction of P with anything
Elimination rule: From a conjunction, infer one conjunct, From a conditional and its antecedent, infer the consequent
Why
Introduction rules put a connective into the conclusion; elimination rules take one out of a premise. The symmetry is deliberate and is what makes the system easy to remember.
Practise Natural Deduction: The Rules
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More questions on Natural Deduction: The Rules
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