As the world economy continues to struggle, people are taking to the streets by the thousands to protest painful cuts in public spending designed to reduce government debt and deficits. This fiscal fury is understandable.

The euro crisis combines, in our view, a sovereign debt crisis and a banking crisis, with mutually adverse feedback between the two. But design flaws in the system magnified their impact and feedback.

The forces of financial and economic fragmentation have widened the divide between countries at the core and the "periphery" of the euro zone. Can this process of fragmentation be reversed?

It is hard to hold the course in the middle of a storm, but European policymakers need to if they want European integration to succeed.