After Ireland's rejection of the European Union's Lisbon Treaty, only uncertainty is certain for the 27-member bloc, reported dpa.
"It's impossible to say what will happen now," Piotr Kaczynski, expert on EU reform at the Centre for European Policy Studies in Brussels, told Deutsche Presse-Agentur dpa.
"There are billions of scenarios being mentioned, from the very dark 'Ireland has to leave the EU' to the other extreme that nothing has happened, the Irish people have spoken, the treaty is dead, let's move on," he said.
The vote makes it virtually impossible for the EU treaty, which is aimed at making the union more efficient and giving it a higher international profile, to come into force by the end of the year, since it needs to be ratified by all 27 member states.
According to Andrea Bonanni, a seasoned EU correspondent from Italy, leaders could be faced with the dilemma of deciding on whether to get rid of the treaty, or get rid of Ireland.
It is not the first time that the EU has seen treaties slapped down by referenda. The Lisbon treaty was created after French and Dutch voters rejected a planned EU constitution in 2005.
And Ireland itself rejected the EU's current set of rules, the Nice treaty, in a low-turnout referendum in 2001. On that occasion, the Irish government called a repeat referendum a year later and chalked up a solid yes on a higher turnout.
But experts say that Friday's turnout, which was on a par with the 50 per cent turnout achieved by the second Nice referendum, will make it very hard for the Irish government to pull off that trick again.
"With the turnout there has been it would be very difficult to hold a second vote, but it's difficult to see what else they can do," Hugo Brady, an expert on EU reform at the Centre for European Reform in London, said.
They also agree that it would be difficult to draw up a successor to Lisbon, since it is itself the successor to a failed treaty.
That being the case, the Irish rejection leaves the EU groping for possible ways to carry on the reform process.
"One option would be to go ahead with separate deals on various issues, such as energy or foreign policy. Another would be for small groups of member states to carry on integration among themselves, and another is that Ireland could be forced into 'second-tier' membership," Brady said.
The Irish vote will have some immediate impacts. Without Lisbon, for example, there will be no new president of the council of EU member states and no reinforced role for the European Parliament.
But the Nice treaty already contains provisions on many of the Lisbon text's more controversial clauses, such as the reduction in size of the bloc's central bureaucracy, the European Commission, and the long-term goal of forming a common defence policy - making it possible for such policies to go ahead even without Lisbon.
"There is room to do things (with the current rules): this is all about confidence. Treaties are not nearly as important as the political will to implement them," Brady pointed out.
Indeed, even as the results of the Irish referendum began filtering in to Brussels, the EU institutions were as busy as ever with other business, commenting on issues from the execution of a 17-year-old in Iran to an agreement on international road transport.
And to some extent experts say that, regardless of the Irish bombshell, business will carry on as usual.
"The vote won't have an impact on commission proceedings: there is no stalemate in the legislative process," Kaczynski said.
Nevertheless, the referendum is sure to overshadow not just a summit of EU leaders in Brussels on Thursday, but the entire French presidency of the EU, which is set to start on July 1.
And with EU members still apparently agreed that the bloc needs a new set of rules to function, the only certainty is that the Irish no is going to open up a long and uncertain debate.
"Governments never do anything in a hurry, and the EU never does quick, dramatic political gestures. It's like in a game when someone kicks over the table, scattering the pieces: all you can do is pick the table up and try to put the pieces back," Brady said.