Seeing Jones

You may say, for example, that you see your friend, Mr. Jones, walking along the street; but this is to go far beyond what you have any right to say.(…) Little packets of light, called “light quanta”, shoot out from the sun, and some of these reach a region where there are atoms of a certain kind, composing Jones’s face, and hands, and clothes. These atoms do not themselves exist, but are merely a compendious way of alluding to possible occurrences. Some of the light quanta, when they reach Jones’s atoms, upset their internal economy. This causes him to become sunburnt, and to manufacture vitamin D. Others are reflected, some enter your eye. There they cause a complicate disturbance of the rods and cones, which, in turn, sends a current along the optical nerve. When this current reaches the brain, it produces an event. The event which it produces is that which you call “seeing Jones”. As is evident from this account, the connection of “seeing Jones” with Jones is a remote, roundabout causal connection. Jones himself, meanwhile, remains wrapped in mystery. He may be thinking about his dinner, or about how his investments have gone to pieces, or about that umbrella that he lost; these thoughts are Jones, but these are not what you see.

Bertrand Russell (on the limitations of the scientific method: Inferences to what is not experienced)
in The scientific outlook (1931)