From a historical point of view, arbitration ex aequo et bono has existed since ancient Greece. Nowadays, it is widely recognized in national laws and arbitration rules. It certainly has a claim of universality in the world of arbitration.
Arbitration ex aequo et bono is a species of the genus arbitration and not a separate principle. The author proposes that arbitration ex aequo et bono be classified foremost as a form of arbitration with a specific decision-making criterion. Such criterion is characterized by the possibility to derogate the positive law. The difference in denominations (ex aequo et bono, amiable composition, equity, etc.) does not indicate a substantial difference in the nature of the principle.