The idea that one should be a camera/microphone recording everything around oneself and saving it for the posterity of future generations. For this purpose listening carefully to people's vernacular and generally observing: how they talk, behave, drink, love, hate; how they dress, what records they listen, what they watch on TV and at cinema, what books they read (if they read at all), and so on and so on. Being an outside observer there; maintaining an illusion of being impartial, of not participating, just watching. Even though this is not exactly true -- probably Bohr and Heisenberg were right with their Copenhagen Interpretation: that even an observer of a scientific test will inevitably have an effect on how the test will turn out, even though having a fallacious illusion of not being a participant there. You see, people tend to act when a camera is present; it's hard to act "natural" when one is aware of being watched. There is no reality-TV.
"Esse est percipi" ("Being is being perceived") - George Berkeley (1685-1753)
The Buggles: 'I Am A Camera' (7" single, 1981)
John Van Druten: I Am A Camera (a 1951 play based on Christopher's Isherwood's Goodbye to Berlin; filmed 1972 as Cabaret, starring Liza Minnelli)