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.

Southern Europe has not done enough to enhance its competitiveness, while northern Europe has not done enough to boost demand. Debt burdens remain crushing, and Europe's economy remains unable to grow.

While holding the eurozone together will be costly and difficult and painful for the politicians, breaking it up will be even more costly and more difficult.

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 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.

The 24% unemployment reached at the depths of the Great Depression was no picnic.

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