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Indirect Method for Implications

Because of ~(G0 => G1) iff (G0 /\  ~G1), it suffices to prove

G0 => G1
K union {G0 /\  ~G1}

"We have to show G0 => G1. Assume G0 /\  ~G1. Then we have ... (derivation of a contradiction)".

Add the hypothesis and the negation of the conclusion to the knowledge and derive a contradiction.

Author: Wolfgang Schreiner
Last Modification: November 30, 1999

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