The Ghosts

I looked around me, and suddenly, it made sense.
“How is it that you can walk through walls while walking on the floor?” I asked one of the ghosts.
The ghost thought for a moment and shrugged.
“I don’t know,” he said.
“Hah!” I shouted. “You don’t exist!”
“I guess you’re right,” said another ghost. They all nodded in agreement.
The next day, when the doctor asked me how I was doing, I told him that the ghosts didn’t exist.
“Oh, really?” he said.
“Absolutely,” I said. “And they agree with me. So, can I go home now?”
Apparently not.