The design of the European Monetary Union has been influenced by various, and sometimes contradictory, economic ideas and doctrines. Among these, Optimal Currency Area theory and Fiscal Federalism, but even more importantly the macroeconomic and monetary framework adopted in Germany under the influence of ordo-liberalism, and the New Classical views about the functioning of market economies, with a clear distrust of political interferences and a strong aversion toward inflation. The European treaties have embedded specific economic doctrines into institutional and precise policy rules. The Great Recession and the subsequent sovereign debt crisis in the Euro Area have shaken these certainties and led to new thinking of macroeconomic and monetary matters.