States pursue their own interest, and are always at risk of being attacked by other countries, wrote Thomas Hobbes in the 17^th century. With the rise of populist impulsive leaders, the world does indeed seem like an increasingly unstable place. We asked Harvard professor of International Relations Stephen Walt about why threat matters more than power, how Trump’s foreign policy is challenging international alliances, and how we created rules to make cooperation easier but have not found a way to prevent conflict where the road is paved with unfriendly intentions. Sitting firmly in the realist school, as he puts it, Walt is concerned with explaining how the world is, rather than how it should be. – Paula Erizanu

PE: What were your first thoughts when you read about the US agreement with North Korea, and Trump’s recent declarations accusing Western allies for abusing the US through tariffs at G7?