A Philosophy class was holding its final exams. When testing time came, the professor asked everyone to take out a sheet of paper. He then placed a chair on a table in the front of the auditorium, and gave the students one simple task. "For your final exam," he said, "Tell me how this chair doesn't really exist."

Almost immediately, a student walked toward the front of the class and handed his paper to the professor and walked away. The professor stared blankly at the response on the paper- "What chair?"