“Indeed, the line between perceiving and hallucinating is not as crisp as we like to think. In a sense, when we look at the world, we are hallucinating all the time. One could almost regard perception as the act of choosing the one hallucination that best fits the incoming data, which is often fragmentary and fleeting. Both hallucinations and real perceptions emerge from the same set of processes. The crucial difference is that when we are perceiving, the stability of external objects and events helps anchor them. When we hallucinate, as when we dream or float in a sensory deprivation tank, objects and events wander off in any direction.”