A logically possible proposition is one which is consistent with the axioms of a given system of logic. In other words, the logical possibility of a proposition will depend on the system of logic being considered, rather than violation of any single rule. Some systems of logic tolerate inconsistent propositions or even true contradictions, while other logical systems have truth-value gaps instead of a binary of such values. However, when talking about logical possibility it is often understood that the system in question is classical propositional logic.