At the final exam, the philosophy professor places his chair on his desk and instructs the class, "Using every applicable concept you've learned in this course, prove to me that this chair does not exist."
The students are all busily writing in their blue books, proving that this chair doesn't exist, except for one student. He writes his answer in thirty seconds, then turns his exam in to the astonishment of everyone.
In a week, grades are posted, and to the amazement of the class, the student who wrote for thirty seconds gets the highest grade.
His answer to the question: "What chair?"
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