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.

For German Social Democracy, Europe is vital to the national interest.

Turkey is doing an enormous amount in the refugee question, but it can't continue to pay for everything by itself. That is why we have to talk to Turkey about money.

I want to end tax dumping. States that have a common currency should not be engaged in tax competition. We need a minimum tax rate and a European finance minister, who would be responsible for closing the tax loopholes and getting rid of the tax havens inside and outside the EU. It is also clear that we have to reach common standards in our economic and labor policies. We cannot continue to just talk about technical details. We have to inspire enthusiasm in Germany for Europe.

At the time, Jean-Claude [Juncker] was already an important man in Brussels. I was a young representative in the European Parliament. We talked for a long time and from that point on, our connection became increasingly deep. But our working-class origins are at least as important to our bond.

Ms. Merkel is avoiding retirement issues. She simply doesn't want to do anything, although she knows that doing nothing means that real pensions will fall. That is preprogrammed old-age poverty. When it comes to wage fairness: It was Ms. Merkel herself who blocked the establishment of a right to return to a fulltime job after going part time for a period. Yet everyone keeps saying that our platform is identical to that of the conservatives. It's crazy.

Donald Trump has made the principle of purposely breaking a taboo into a means of achieving his political objectives, which is something that he has in common with Turkish President Recep Tayyip Erdogan and Hungarian Prime Minister Viktor Orbán. Trump systematically violates international rules. But we cannot allow ourselves to forget that Trump is not the U.S.