The word ‘perception’ can be used in two different ways. It can refer to our experience of seeing, hearing, touching, tasting, and smelling objects and individuals around us. It can also refer to the processes that allow us to extract information from the patterns of energy that impinge on our sense organs. Thinking about perception as a set of processes has the advantage that it includes situations where there is no subjective experience. ‘What is perception?’ explains that sometimes our perceptual systems can be fooled and we experience illusions. Is this because of past experience and our knowledge of the world, or is it that we are not extracting the information in the patterns of energy reaching our senses?