Only solidarity can save the euro now

When European Central Bank president Mario Draghi proclaimed that the ECB would do "whatever it takes" to ensure the future stability of the euro, borrowing costs fell for Italy and Spain, markets rallied, and the decline in the external value of the euro was checked.

It remains unclear how long-lasting the effects of Draghi's intervention will prove to be. What we can say with certainty is that Draghi's remarks and the reaction they evoked demonstrate that the fundamental problems of the euro zone are not primarily financial or economic; they are political, psychological and institutional.

International observers took such notice of Draghi's commitment to do "whatever it takes" to save the euro because so many of them have come to doubt other leading European players' commitment to do likewise.

In their own defence, euro zone ministers point to the raft of reforms introduced over the past 30 months. Unfortunately, these reforms have failed to answer unambiguously the question posed by international markets: are the euro zone's largest and most prosperous members absolutely committed to its continuation?

No one doubts that Germany and most other euro zone members would prefer the single currency to continue. Today's uncertainty concerns whether this preference may be overridden by considerations of national politics, or resentment at the slow pace of reform in certain countries.

While the euro zone's richer countries have indeed done much to help their troubled neighbours, they have done so in an obtrusively conditional, transitional and incremental fashion.