This is good question to ask of someone who is seeing things you cannot see. It makes me think of a story my zen friend told me about a girl who believed she was covered in snakes. She was convinced that snakes were writhing all over her despite the fact that no one else could see them. They called doctors, who tried to show her that there were no snakes there. They tried any manner of healers who all tried to show her that there were no snakes, that she had nothing to be afraid of. Finally, someone came in – probably a zen monk, given the source of this story – and he says, “Tell me about the snakes. Help me see them. Describe them to me Let’s get to know those snakes.”
And of course, they disappeared.