 The system FDE is a well-known system of relevance logic (see the entry on  relevance logic)  and it shares with other relevance logics the property of being a paraconsistent logic, see the entry on  paraconsistent logic.  Paraconsistent logics fail to satisfy the unrestricted ex contradictione rule, which is usually presented in a multiple-antecedent framework by the sequent:  \[ A, \osim A \vdash B.\] 