This question, a favourite among amateur philosophers, was posed by Beldin to the disgust of Belgarath. What is the answer to the riddle, though?
Polgara claimed that if there's a noise in the forest, there is always someone around to hear it, and Ce'Nedra backed her up by saying that the trees can hear. It seems to me that Polgara and Ce'Nedra had missed the point of the question a little. While a forest always has trees in it (by definition), and nearly all forests have some sort of life in them, the question asks about a forest merely for poetic reasons. To refute their refutation (as it were), I pose a "Gedankenexperiment" with the same philosophical meaning.
Suppose I build a room, and somehow make it soundproof. I fill the room with a mixture of poison and disinfectant (to eradicate all form of life from the room - if this bothers you, just remind yourself that it's no worse than Schroedinger's inhumane thought experiment with a cat), empty it, and put a sterilised, functional alarm clock in it. I then leave and seal the room, so nothing else gets in or out of the room. The alarm clock is due to go off at noon. When noon comes, has the alarm clock made a sound?
I hope that Polgara wouldn't claim that the above scenario is impossible; it is implausible, certainly, and highly contrived, but it could clearly be carried out by someone with enough time, money and patience.
So, the question remains; has the alarm clock made a sound? To a certain extent, the question is only one of definition. If you define sound as a longitudinal wave with a frequency between 16Hz and 20kHz (say), then the alarm clock has made a sound. If you define sound as something that can be heard, then the question is slightly more complicated.
The scenario has been constructed so that no sound is heard by anyone or anything, but it is clear that if I open the door to the room, I will hear the alarm clock. So either opening the door causes the sound of the alarm clock to exist, or the alarm clock was making a sound all along.
The first of these alternatives seems a little unlikely to me, but it is reminiscent of situations in quantum physics (where observing an action on the sub-atomic scale can cause the action to change), so should not be dismissed out of hand.
Still, I think Beldin could have found better matters with which to concern himself. There are still the vexing questions of "what is the sound of one hand clapping?", "what noise does yellow make?" and the liar paradox ("is 'this statement is false' true or false?) to resolve. And of course, we mustn't forget the question once posed by Rumor when we were last discussing sounds in the wood: "what is the difference between a duck?"
Written by Simon Nickerson