Upon learning that I'm studying Buddhism, people have asked me, "What is the sound of one hand clapping?" Recognizing that the question is from a Zen koan (and I haven't really studied Zen) and isn't a generically Buddhist question, I think my answer is this: The sound of one hand clapping neither exists nor does it not exist. It cannot be said to exist because one hand striking against nothing makes no sound, nor can it be said not to exist because (like the antlers of a rabbit or the child of a barren womb) it can be referred to. This illustrates the Buddha's "Middle Way" between idealism (the sound exists) and nihilism (the sound does not exist) to an understanding of reality. Rightly seen, reality is a delusion--it has no unconditioned self-nature--but even a delusion can be said to exist.

This is based on my grapplings with The Diamond Sutra, in which we learn that once the distinction is drawn that creates existence and non-existence, all is deusion. I'm getting to the point of being able to talk the talk (if not very clearly), but that isn't helping me to walk the walk.