Homo sum: humani nihil a me alienum puto.” (I am a human being. I consider nothing human foreign to me.) These words by Terence, a second century BC Roman playwright, make a noble motto for our time. They define a position condemned by many, including the president of the US, as “globalism”. Yet that should mean more than economic — or, as some call it, “neoliberal” — globalisation. It should mean that humanity has global obligations and interests. To meet the former and promote the latter, the nation state is the start. But we must also think and act far beyond it.

This has been brought home to many by photographs of Earth as a brilliant blue marble suspended in space. These were the culmination of half a millennium of exploration and scientific discovery that brought Terence’s words to life. Human beings are closely related. They are a part of a complex web of life. They share a planet that is the only one in the solar system that carries life of any kind. There may be more life like us elsewhere in the universe. But so far we have not found it. We are alone.

This should on its own make us think globally. But there are other reasons to do so, both moral and practical.