 All right, all right. Before we get ahead of ourselves, yes, magic mushrooms are associated with hallucinations, much like those experienced by the Australians who ended up in hospital, the thing that we started the show with. Here we have David Nutt, professor of neuropsychopharmacology at Imperial College London here in the UK, and he's here to help us navigate everything hallucinatory. Hello, David. Good afternoon. All right. So, of course, I'm going to start with the obvious question. What is a hallucination?