A national currency is both a symbol of sovereignty and the key to the pursuit of an independent economic and budget policy.” (Feldstein, 1997, p. 3.) A special feature of European monetary union will, in fact, be that it will not have a complementary political union - at least in the foreseeable future.
And that is because it fully reflects and respects the letter as well as the spirit of the European Treaty and therefore of the principles that I stressed at the beginning. The current crisis is most certainly a defining moment for monetary union.