What are thoughts? Where do they come from – and where do they go?

What are thoughts? Where do they come from, and where do they go when they disappear? Are they “filed” somewhere, a bit like memories, where we can find them again, or once a thought has gone is that it?
Sue Christian, Oswestry

Post your answers (and new questions) below or send them to nq@theguardian.com. A selection will be published on Sunday.