Getty Opinion Europe, end your infernal muddle! Clarity, not ambiguity, will save the EU from collapse.

This is the nightmare that keeps Europe’s leaders up at night.

After years of muddling through — neither allowed to default nor to get back on its feet through austerity and haircuts — Greece leaves the euro. Russia promptly steps in, in exchange for Greece ending its support for EU sanctions. The Eastern European states become anxious, and a newly elected Kaczynski government in Poland further questions EU integration, turning the renegotiation on British membership into an impossible endeavor. The British public recognizes this by voting Britain out of the EU. The European idea and the European continent is in pieces.

This scenario shows something that is too rarely acknowledged: Europe’s problems are interlinked — one domino falling may bring the rest down with it. On the surface the thread linking all these seemingly disparate crises is that they have landed on Angela Merkel’s desk.

That is unsurprising: They are there because they are ultimately about Europe’s credibility, or rather its absence. When Europe is divided or drifting, people look for something solid to hang onto. Berlin has become a political anchor not just because of its economic strength but because Merkel has been able to engineer that rare political commodity: European unity.

Merkel, whose modus operandi is “leading from the middle,” now has a chance to change the nature of that unity. European decision-makers have long seen “creative ambiguity” as one of the secrets of their success. From Jean Monnet to Merkel, European leaders have used ambiguity to transcend divisions and keep the European show on the road. Should Turkey join the EU or not? Will European defense rival or complement NATO? Will Europe be a free trade area or a federal state? These questions have never been definitively answered.

As Europe’s power has receded, its careful fudges have been tested. Turkey no longer believes it will join the EU. The Greek crisis became critical when markets questioned whether the EU would stand behind Athens’ debt. Putin felt he could afford to annex Crimea because the West would not respond decisively. And Britain’s Euroskeptics were emboldened by the ambiguous attitude of their government to the EU. Shallow unity behind empty phrases is a fine strategy in good times — but when times are tough they are a recipe for disaster.

So is it possible for Europe to restore its credibility and avoid the nightmare scenario?

This will be a key question for the 100-plus European politicians and policymakers who gather this week for the European Council on Foreign Relations’ Annual Council. The first step is retreating from implausible promises and consolidating behind defensible positions. The goal should be “sustainable unity” rather than hiding the differences between member states.

Stopping the first domino, Greece, will require real courage. Neither the Greek economy nor its people can tolerate creative ambiguity any longer. The EU has to give Athens a clear way out (a default) or a clear offer to stay in (a debt cancellation/extensive haircut).

Second, we need to be more honest with ourselves about our plans for Russia. So far the EU has held together — just — behind the sanctions that were imposed after the downing of Malaysia Airlines Flight 17 and empty phrases about the “Minsk process.” These talks are pursuing a 50-year policy of “neo-containment.” But how can you “contain” your biggest energy provider? And is it realistic to expect the EU’s reluctant sanctioners — Austria, Italy, Greece and Cyprus — to uphold a purely punitive approach towards Moscow? At the same time, the EU cannot legitimize Russia’s annexation of Crimea or tolerate its continued incursions into Ukrainian territory in the East. A twin approach to Russia could be a solution — be tough on Russian transgressions, if needed through stronger sanctions — but let Russia play a role on the Eurasian continent, through negotiations and working with the Eurasian Union.

Third, Britain’s EU membership can only be preserved with clarity on both sides, starting with the British side. For five years, Prime Minister David Cameron has been ambiguous on whether he would be the leader of the “in” or the “out” campaign. At the G7 meeting in Germany, Cameron finally made it clear that he sees his role as keeping Britain in the European Union. Now that he has nailed his colors to the mast, other EU leaders can trust him more to fight to stay in rather than demanding concessions to appease his Euroskeptic backbenchers.

Other EU members can now use this new opening to turn the British desire for reform into a quest to improve the EU for everyone, rather than focus on British exceptionalism. Everyone will benefit if reforms can be found to rebuild credibility for the principle of free movement by helping the losers in different member states; by reassuring the eurozone and euro-outs that their interests will be served fairly by EU institutions; and by giving citizens a greater sense of control over their fate. And if the British public vote to stay, their government will be freed to be a constructive member of an outward-looking Europe rather than the semi-detached irritant it has been in recent years.

The EU faces many challenges — but these could be an opportunity. Diminishing credibility and rampant creative ambiguity have brought Europe to the brink. By clarifying what it stands for, what it wants to achieve and how it’s going to achieve it, Europe can stop the dominoes from falling.

Mark Leonard is co-founder and director of the European Council on Foreign Relations.