Across the continent, political divisions are deepening. For all of these reasons, the specter of a euro zone collapse has not been dispatched.

As for the single market, the E.U.'s landmark achievement, there is no question that a euro zone breakup would severely disrupt its operation in the short run.

The consequences of a collapse would not be pretty. Whichever country precipitated it - Germany by threatening to abandon the euro, or Greece or Spain by actually doing so - would trigger economic chaos and incur its neighbours' wrath.

The 1992 crisis proved that the existing system was unstable. Not moving forward to the euro would have set up Europe for even more disruptive crises.

Political union means transferring the prerogatives of national legislatures to the European parliament, which would then decide how to structure Europe's fiscal, banking, and monetary union.

I hope Greece is going to remain in the Euro zone.