There are tens of millions of people in the world who have fled their homeland because of war or persecution. But there are millions more who cross borders to be with family, to retire to a warm climate, or to earn more money. Countries have the right to restrict immigration, at least in theory. The question is whether they should have this right.
This week the BBC begins a new experiment in philosophy, The Global Philosopher, presented by Michael Sandel. The programme uses a state-of-the-art studio at the Harvard Business School in Boston, which allows people around the world to come together for a global discussion. Here producer David Edmonds sets out some philosophical puzzles connected with borders and immigration.