Hallucination is being confined to a classroom, at Georgetown University. The course catalog gives details:
We all make mistakes. We all sometimes remember things that didn’t really happen and sometimes forget things that really did. We all get confused by optical illusions, and phantom pains and itches. We all sometimes believe false things other people tell us. We all sometimes confuse our dreams for reality. We all sometimes believe things because we really want them to be, even though we have good reasons for thinking they aren’t. And sometimes we’re just plain hallucinating.
How can we be sure that we’re not mistaken about everything? What kinds of thing can we know for sure? What is knowledge anyway? We’ll look at some old, not so old, and even less old answers to and ways of thinking about these questions.
(Thanks to investigator Scott Langill for bringing this to our attention.)