We're at a historical juncture: A growing number of people are declaring what has been achieved over the past decades in Europe to be wrong. They want to return to the nation-state. Sometimes there is even a blood and soil rhetoric that for me is starkly reminiscent of the interwar years of the past century, whose demons we are still all too familiar with.

I'm proud of the fact that Marine Le Pen in France insults me and Geert Wilders in the Netherlands calls me his opponent. The way I see it is, if these people weren't attacking me, I would be doing something wrong.

Things are going well in Germany because the economy is booming and as an export-driven nation, we are profiting from the fact that we have an excellent, high-performing SME sector. But if we want things to continue to go well into the future, then we have to break up the antiquated structures in some areas and really modernize.

At the end of the day, men like Donald Trump need to be given that which they themselves dispense: clear messages. I would confront him as clearly and explicitly as possible. It is not only the right, but also the duty, of the leader of a German government to do that.

Referendums have always posed a threat when it comes to EU policy, because EU policy is complicated. They're an opportunity for those from all political camps who like to oversimplify things.

The construction of social housing and the attempt to support families seeking to buy their own homes are all projects from the 1960s and '70s. It all sounds old-fashioned, but it is actually completely modern.

Businesses will only invest in Greece if three conditions are fulfilled. First, there must be a clear commitment to the euro. No businesses will invest if they have to fear that Greece will leave the euro zone at some point. Second, the Greek government must be prepared to work together with European institutions in order to restructure the country.