It is their boundaries that define the area within which money serves the public as a means of exchange, a unit of account and a store of value. Seen from this perspective, the conclusion seems natural: if money is a public good at the level of the Single Market, then it is at that same level that a single currency should be established.
In the context of the Single Market, the establishment of a single currency was the way to ensure that citizens would benefit in full from all the functions of money. Far from removing money from people, monetary union has given it back to them. A second contract That the euro has economic origins does not reduce its significance as a social contract.