“The idea that intelligence could be quantified, like blood pressure or shoe size, was barely a century old when I took the test that would decide my place in the world. But the notion that intelligence could determine one’s station in life was already much older. It runs like a red thread through Western thought, from the philosophy of Plato to the policies of UK prime minister Theresa May. To say that someone is or is not intelligent has never been merely a comment on their mental faculties. It is always also a judgment on what they are permitted to do. Intelligence, in other words, is political.”