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.

The dangerous glorification of the nation state, and the baiting of minorities that goes along with it, releases an anti-democratic energy.

Political leaders need to formulate long-term EU goals that show: Yes, we want to stay together.

When it comes to climate protection, the whole world will have to pay the price. But if Donald Trump intends to conclude a trade agreement with the EU, he will have to abide by our climate standards. In any case, waiving climate protection does not make American products more competitive.

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.

The question of societal fairness is always pertinent.

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.