Europe’s wasted every crisis it’s faced: the sovereign debt crisis, the Syrian exodus, and the Paris terror attacks could all have been used to make the case for federated European institutions needed to put an end to this rolling catastrophe.

I have written before that those of us who believe in the United Kingdom as a union between nations ought to support a single, European state on the same principle: that nationality can be transcended by common goals and institutions.

If one is British, it’s not a big leap to be European. But nationalism only persuades nationalists. How to make an optimistic case for the EU when it has failed to settle any of its major crises?

Germany has been left alone as the de-facto leading power because Britain and France have been scrutinising themselves rather than leading in Europe. Germany’s interests have been protected at the expense of others.

Ideally, Europe ought to represent itself. But so long as national leaders act as Europe’s executive, a balance of power ought to be maintained to scrutinise proposals of continental importance.

Southern Europe has advocated on its own behalf to a disproportionally powerful Germany. Europe’s malaise has been prolonged as a result. A party on Germany’s level like Britain or France should have advocated federated solutions in Europe’s collective interest.

Right now, whether we vote remain or leave, we are not voting on a settlement but on a trajectory. Those of us who are comfortable with further integration will vote in. Those who want to cease further European integration may vote to tug us out. How to reconcile these two parties into a ‘remain’ vote?

Of the two choices only leaving definitively closes the sovereignty question. ‘Remain’ is open ended if we don’t know what the EU will look like next year, let alone a decade from now. Cameron ought to be arguing for a constitutional settlement on the rights of peripheral states, not for a parochial set of opt-outs on a nation-by-nation basis.

This would put a barrier on further integration without sacrificing the union. Opt-outs are not definitive enough: not to form a stable foundation for the Eurozone to build on, preserve Britain’s international standing. or to put anti-federalists at ease.

After ‘No’ won in Scotland, separatist sympathy grew because the Prime Minister pulled English votes for English laws out of a hat. The vote Scotland had wasn’t about what Cameron eventually offered.

If the ‘remain’ camp is going to win this referendum and close this question for good Cameron has to tell us what Europe is likely to look like in the next decade or more: split between the Eurozone core and a confederated periphery.

The core eventually has to come to an accord on its common institutions or fall apart entirely. Far better that peripheral states codify a shared vision of what rights they should share now than leave it until the last moment, when the core will have their own vision. What powers do the periphery consider to be best reserved for their own institutions?

If these powers are constitutionally codified, the unification of the core cannot come about by their subversion. Europe’s periphery should become its vessel, shaping it from the edge.

Those who want to join the core with all it entails could opt in later, and those who don’t can stay on the outside.

‘Repatriation of powers’ is a red herring, and will not settle the question of sovereignty or preserve Britain’s competitive advantages. Cameron’s negotiation should be aimed at defining what the outer ring of a two-speed Europe should look like.

* Toby MacDonnell is a Lib Dem member. He is a graduate in history from Sussex university reading Keynes and Baudrillard in preparation for postgraduate studies.