I read Scuzz's last post about quantum theory where he used the thought-experiment of "if a tree falls in a wood and no one is around to hear, does it make a sound?" to discuss a really important issue. What struck me is how this sparked a problem thousands of years ago and again 17th and 18th centuries and how it's almost beautiful that it's been brought up again but this time as a possibility that we might actually be able to solve this problem scientifically.
In philosophy this has been of such a great debate between rival 'schools' of thought: the Realists and the Idealists. The best proponent for the Idealists I can think of is Berkeley: a the common theme running through his works is that the world as we know it is only what we can perceive (experience). We can only ever be directly aware of our perceptions, nothing else. We can not directly experience a tree, a table or an apple without using our senses. If you remove our ability to sense, the ability to prove the outside world is impossible.
In answer to the question, "does it make a sound?" the answer is no - sound as we know is an experience and if there is no one around to experience it then there is no sound. It literally means that we cannot prove that it exists or it fell. However, it does not conclusively prove that it doesn't exist or it didn't fall. We might say that it exists as a 'possibility': that it is neither impossible nor impossible, it could happen.
Interestingly, with quantum theory we are getting information that these sorts of things don't have to be exclusive anymore. There is evidence that some atoms can simulateneously occupy more than part of space or that if we observe it, it can completely alter the data we receive. No longer is it just thereotical.
