A philosopher once had the following dream.
First Aristotle appeared, and the philosopher said to him, "Could you give me a fifteen-minute capsule sketch of your entire philosophy?" To the philosopher's surprise, Aristotle gave him an excellent exposition in which he compressed an enormous amount of material into a mere fifteen minutes. But then the philosopher raised a certain objection which Aristotle couldn't answer. Confounded, Aristotle disappeared.
Then Plato appeared. The same thing happened again, and the philosophers' objection to Plato was the same as his objection to Aristotle. Plato also couldn't answer it and disappeared.
Then all the famous philosophers of history appeared one-by-one and our philosopher refuted every one with the same objection.
After the last philosopher vanished, our philosopher said to himself, "I know I'm asleep and dreaming all this. Yet I've found a universal refutation for all philosophical systems! Tomorrow when I wake up, I will probably have forgotten it, and the world will really miss something!" With an iron effort, the philosopher forced himself to wake up, rush over to his desk, and write down his universal refutation. Then he jumped back into bed with a sigh of relief.
The next morning when he awoke, he went over to the desk to see what he had written. It was, "That's what you say."
[From Raymond Smullyan, 5000 B.C. and Other Philosophical Fantasies. St. Martin's Press, 1983]