A few months ago, I fell on a column that Fairfax had left lying around. When Waleed Aly wrote, “Left and right have almost never been meaningful terms,” I took a little spill. Well, as you know, you just can’t be too careful at our age; even a mild injury can produce ongoing pain. Today, after a more serious public failure to define left and right, I am in traction.

This is not, entirely, a personal ache. It is more broadly social. You just can’t go about saying that historic and articulated political differences mean nothing, never have, and expect all future discussion to go on in good health. Whether you’re a friend of Marx, a member of the Mont Pelerin Society or just someone with a vigorous interest in policy, left and right must retain their meaning.