Repugnancy: clear, irreconcilable inconsistency between laws triggers displacement when coexistence is impossible. Repugnancy denotes inconsistency between enactments and is established where there is a clear, direct and irreconcilable inconsistency producing a collision that makes obedience to one law impossible without disobeying the other; repugnancy may also arise where a superior legislature demonstrates an intention to occupy a field exhaustively, and in the Concurrent List context the doctrine of pith and substance is applied to determine whether both laws substantially relate to the same subject.