Monetary union will not just abolish the exchange rate instrument domestically. It will of necessity also call for a single domestic and external monetary policy, and thus a common stance in a key policy area. For the euro area, however, achieving and maintaining a common stance of this kind will undoubtedly be more difficult than for a traditional national currency area.
Whereas the currency will be supranational, it will generally remain the individual governments that will be taking the decisions on economic and social policy. That is all the more reason why the euro needs dominant patterns of preference which are common to all participants. That likewise implies the affirmation of major fundamental positions.