The observer, when he seems to himself to be observing a stone, is really, if physics is to be believed, observing the effects of the stone upon himself.
— Bertrand Russell

There are over five and a half billion cell phones in the world, nearly all equipped with cameras: an orgy of recording of life as it passes. Our age has seen an explosion of this peculiarly human activity — recording activity — on a scale scarcely comprehensible even by those who've lived through it. What changes has this revolution wrought, not only in how we see the world, but how we live in it?

Not so many years ago, taking a photograph was a painstaking business; film was expensive, and there were no do-overs. The ordinary person might take a few rolls, say 96 or 144 or 288 exposures over the course of a holiday, composing each one with the greatest patience and care; they were very easy to spoil, since the camera could be opened again only when the film had absolutely for sure been rewound all the way. Then each roll was lovingly stored in its own little canister, away from extremes of temperature, and once home, they were dropped off at a processor, or sent by snail mail in special mailers; many anxious days would pass before the results came back, the occasion of hard-won rage or bliss scarcely imaginable today.

Nowadays one takes hundreds of images in an afternoon without a moment's thought. The suspense over whether or not a photograph "came out" lasts for seconds, not weeks, and if it didn't come out we can often try again, five times, a dozen times.

No other earthly creature tries to keep something of its own vanishing moments — that we know of, I mean. Who knows what Unamuno's crab might not get up to, in his spare time. That is one great difference that separates us from other animals. Later developments indicate another, newer and more complex difference: we are increasingly conscious of the nature and purposes as well as the ultimate futility of the attempt.