Anthropologists have found that all over the world people believe that their minds are transparent to gods, saints, ancestors or other spirits. This is also true within the Christian tradition. As Europe became more secular in the 18th and 19th centuries, the idea that minds were transparent was secularised in novels, with the novelist having a view of the inner workings of other people's minds. And now our emails, phone calls and activities are under continuous surveillance, making this ancient belief a technical reality.