The difficulties we have found in our common sense views of vision pertain not just to the seeing of distant objects such as stars but to all cases of seeing. Even when we observe things close up, information about them is contained in the light waves that they reflect or emit. The perceiver gains access to this information as a result of his eyes being affected by light which thereby triggers a series of inner episodes in his nervous system and brain. Observation has a quite different meaning in the scientific story than it has for common sense. The directness and immediacy by which we seem to be visually in touch with the "external world" is, for the scientific story, just an illusion. What we call 'seeing something" is not a simple inspection of an external fact, but the production of a chain of inner events which then are interpreted in order to extract their informational content.