It's a well known question, generally followed by the instinctive answer, "Of course it does!"
Then, perhaps, a short pause and point taken. "But you're asking how can I myself be sure if I am not there to hear? And if no one is there to hear, how can anyone be sure it makes a sound?"
Well, it's common sense that it would make a sound.
Common sense? What's that? Common sense like the common sense that tells some people the world is flat - that if it were round, we'd all fall off? Anyway, isn't saying it's common sense just a way of saying what people often say in the first place - that of course it makes a sound?
That's silly. Everyone knows a tree falling in a forest, empty or not, would make a sound and if you weren't there yourself - if no one was there - it would still make a sound. You could easily put a tape recorder or something there to prove it. And when the tree fell you could hear it make a sound. It stands to reason.
But that's not a sound reason - it's just another way of saying it makes a sound. Putting a tape recorder there is just putting ourselves there when we're not there. It's not an answer to the question because we have to be here to put the tape recorder there. We've got to be there or put something we've made there - to prove a tree falling in an empty forest makes a sound.
Look, I've got more important things to do than talk about this. I'm off to stare at a brick wall for an hour.
I know it seems silly, but it's actually important.
Important? What's important about trees falling in empty forests?
It's whether they make a sound. What the question means is we can't prove an external world exists outside us.
What!? Does the world exist ...? That's the most ridiculous thing I've ever heard. Of course it does!
