I guess there is context too; if there was a monkey in the corner I'd check that I was really seeing it, though I don't doubt my sanity or think I hallucinate ever. Presumably, if someone then told me the monkey did not exist, that would be part of my repertoire and I could answer your psychiatrist, "Well, I saw this monkey in the corner of a room once that no one else seemed to. . ." Anything I saw that I had not seen before (I'm not in the habit of seeing monkeys in the corner of rooms) would get me to note it and ask, "Hey, what's that monkey doing in the corner of the room?" If the monkey belonged there, Ross from "Friends" would say, "Oh, that's Marcel, my capucin monkey friend!"

I think people know when they hallucinate, after they finish with that particular hallucination? It wouldn't be normal for the little man you see from the corner of your eye to follow you around inside your house as well as outside? You or someone else would have to let him in the house/see him enter. I'd be suspect of anything I never quite see clearly but that occupies my thinking; you see something out of the corner of your eye, look to see what it is and if it is not really there, it shouldn't show up again and, if you can't get a clear look at it you may not be sure you saw it but you won't take it further than that, imagining it is you that has the problem (it's there and out to get you even though you can't see it)? If I were to take it further, attribute something to something I could not see clearly, I'd be able to say, "well, there's a little man I can't quite get close enough to question and he keeps showing up inside my house. . ." It would not matter that I believed/knew the little man was there, other people would have told me he isn't/they don't see him.