In political life, it is extremely difficult to remain loyal to a friendship when constellations of power or interests are in the way.

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.

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.

If we want to defeat Islamic State, we first have to arrive at a cease-fire agreement in Syria. Once that has been achieved, an anti-IS coalition can be assembled, including Russia, Saudi Arabia and Iran. That, however, will be significantly more difficult in the wake of Turkey's downing of the Russian plane.

The claim made by Hungarian Prime Minister Viktor Orbán that the refugee question is a German problem is incorrect. It is a European problem.

If you say in advance there is going to be a main candidate and then that doesn't count later, then that's going to be a highly problematic occurrence in a democracy.

It became obvious that we had completely failed to impose rules on unbridled speculative capitalism. That destroyed financial systems, hollowed out state systems and deeply shook German social stability. Can you recall the debate about "locust" hedge funds - even if it's a terrible term. The speculator capitalists roamed the land, stealing the substance from companies and throwing away the shells. And we were powerless.