Once a year I teach a class that divides friends, confronts ideologies, and challenges us all to change our minds. I get to the seminar room early, pull the chairs out of their neat rows and split the seating into two long columns divided by an aisle, rather like the seats on an airplane. As the students start arriving, they are confronted by a single question on the screen: Is green growth possible? Yes / No. I ask them to take a seat in answer to that question: for Yes, sit in the column by the window; for No, sit in the column by the door. And standing in the aisle is not allowed.
