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formal proof

A step-by-step derivation of a conclusion from premises using stated rules.

A formal proof (derivation) is a numbered sequence of sentences in which each line is a premise, an assumption, or follows from earlier available lines by one of the proof system's rules, cited by name and line number. The last line, outside every subproof, is what is proved.

Examples

  • A three-line proof: 1 P → Q (premise), 2 P (premise), 3 Q (→E 1, 2).

See also

natural deduction rule of inference subproof
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