It's not attractive at the moment to vouch for the European idea. I still do it, because I believe nothing would be better for our continent.

Turkey has in interest in finding agreement on more permissive visa requirements, it wants to be recognized as a safe country of origin and it wants to finally return to constructive EU accession negotiations. We Europeans decide all of those things together.

If we want to create new rules of globalization, then we can't just think in terms of the nation state. The nation state has long offered protection. But it suffers from the fact that many citizens increasingly fear that it can no longer protect them: The threat of transnational terrorism is growing. Freedom of movement rules in Europe facilitate social dumping. Regardless of the make-up of the next government, it must have clear ideas on how to overcome the lack of direction of recent years.

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.

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.

Donald Trump is betraying everything that made America great: tolerance, democratic institutions and respect for the individual. In that sense, Trump is the most un-American U.S. president that the country has had in a long time.

I try to speak in a manner that allows people to tell me apart from my political adversaries. And I speak in a manner that the people can understand. For me, that isn't populism.