Where are we now in this process?
The outlines of the missing ingredient, namely a common treasury, are beginning to emerge.
They are to be found in the European Financial Stability Facility (EFSF) - agreed on by twenty-seven member states of the EU in May 2010 - and its successor, after 2013, the European Stability Mechanism (ESM).
But the EFSF is not adequately capitalised and its functions are not adequately defined.
It is supposed to provide a safety net for the eurozone as a whole, but in practice it has been tailored to finance the rescue packages for three small countries: Greece, Portugal, and Ireland; it is not large enough to support bigger countries like Spain or Italy.
Nor was it originally meant to deal with the problems of the banking system, although its scope has subsequently been extended to include banks as well as sovereign states.
Its biggest shortcoming is that it is purely a fund-raising mechanism; the authority to spend the money is left with the governments of the member countries.
This renders the EFSF useless in responding to a crisis; it has to await instructions from the member countries.