Jerry Lettvin used to tell a story, to support his contention that students were no longer being taught how to <i>think</i>. He said there was a grad student at whose orals Jerry was one of the professors. Before the student arrived, Jerry noticed a beverage bottle sitting in a window, with the sun shining on it. He went to the window and rotated the bottle 180°, and sat down. The student came in, and Jerry asked him to examine the bottle. "Which side is warmer?" Jerry asked. The student replied that the side facing away from the window was warmer. Jerry said, "Explain this."<p>To my recollection, Jerry didn't relate the student's response, but from the way he told the story I gather it was unsatisfactory.