For as long as we've studied the mind, we've believed that information flowing from our senses determines what our mind perceives. But as our understanding of neuroscience and psychology has advanced in the last few decades, a provocative and hugely powerful new view has flipped this assumption on its head. The brain is not a passive receiver, but an ever-active predictor. At the forefront of this cognitive revolution is philosopher and cognitive scientist Andy Clark, who has synthesised his ground-breaking work on the predictive brain to explore its fascinating mechanics and implications. Among the most stunning of these is the realisation that experience itself, because it is guided by prior expectation, is a kind of controlled hallucination. This even applies to our bodies, as the way we experience pain and medical symptoms is shaped by our expectations.