Idempotency of entailment 2002370 190776564 2008-02-12T02:02:11Z Gregbard 1193764 logical system using [[Project:AutoWikiBrowser|AWB]] {{Confusing|date=December 2006}} '''Idempotency of entailment''' is a property of [[logical system]]s that states that one may derive the same consequences from many instances of a hypothesis as from just one. In sequent calculi this property can be captured by a [[structural rule]] called '''contraction''' and in such systems one may say that entailment is idempotent just in case contraction is an [[admissible rule]]. Rule of Contraction: from A,C,C -> B is derived A,C -> B. Or in [[sequent calculus]] notation, :<math>\frac{\Gamma,C,C\vdash B}{\Gamma,C\vdash B}</math> [[Category:Logic]] {{philo-stub}}