The strange world of sight

now, 100 years later, because it seems so implausible. Yet it tells us something very important – that perceptions are not identical with what we perceive, and may be very different. The most accurate historical account of perception is that of the 19th-century German scientist Hermann von Helmholtz. However, it was ridiculed at the time. Von Helmholtz thought that perceptions are unconscious inferences we make based on a combination of clues provided by the eyes and other senses, and knowledge of the world. This idea of unconscious inference for perception preceded, by several years, the psychoanalyst Freud's notion of the unconscious, which was also initially treated with derision because it undermined the notion of human as pre-eminently rational beings who could be held responsible for their actions and awarded blame or praise accordingly.