Bishop Berkeley espoused the school of thought called Idealism, which went along the lines of: "To be, is to be perceived". One fyne day he dreamt the following conundrum up: "If a tree falls in the forest and no one hears it, does it make a sound?" The implication is that if no one perceives the event, not only does the tree not make a sound, but the tree does not even exist.
This is of course a load of old rubbish. The good Bishop can't do me for defamation since he ceased being perceived in 1753. Had he lived in today's more cynical world, he may well have come up with more relevent thought-experiments to illustrate the philosophy of Idealism, thus:
If a tree falls in a forest:
...and no one is there to hear it, do the other trees make fun of it?
...and it hits a mime, would he make a noise?
...and it hits a census taker, does that count?
...and hits Tony Blair, does anyone care?
...and lands on a lawyer and you can't hear the tree or the screams, will you at least hear the applause?
...and a TV camera doesn't see it, has the tree really fallen?
...will Greenpeace hold a press conference?
For Information practitioners:
...and nobody hears it, is information transmitted?
For Theoretical Physicists:
...and no one sees it, does its wave function become non-localised?