For many people, politics in Brussels and Strasbourg might as well be happening on another planet.

The membership survey was a great moment for inner-party democracy. We can't go back, nor do we want to. Our members are pouring their hearts into this campaign. But people don't join the Social Democrats party just to put up posters. They join because they want to help steer the party.

Now Europe are experiencing a wave of eroding solidarity, first of certain societies and then entire governments. At the same time, we have two giant new challenges to meet: the migration movement and terror. And then Great Britain is thinking about leaving the EU. That should suffice as a description.

If we want to strengthen the EU, then we urgently need a two-pronged approach. First, we can save a lot of money if we finally move to harness synergy effects in military spending. The parallel structures in the individual armies still remain far too costly, and we could save a lot by making joint purchases. Second, we cannot only think in terms of conventional military logic, but instead have to be far better prepared to thwart cyberattacks. Most importantly, we can no longer allow the EU to become bogged down in petty details.

Britain, Europe's second largest economy, a member of the G-7 and the UN Security Council, wants to leave the EU. That weakens us and it weakens Britain.

When a man ends up in the White House who boasts about not having a clue and who says that specialist knowledge is elite nonsense, then a critical point has been reached. Then you will have an obviously irresponsible man sitting in a position that requires the utmost degree of responsibility.

We have committed ourselves to pursue joint policies, but then national governments say, "We aren't bound by that." That is a dramatic situation, because solidarity is a basic principle that cannot be had on an à la carte basis. If we have rules that nobody adheres to, then the community will break apart.