Hall of Infinite Doors
"Now then," the professor says. "Let's say I want to approach this wall," he says, pointing at the wall to his left. You look over and see that it is, in fact, a nice wall, before you divert your gaze back to the professor.
"But what if I can only walk half of the distance I have previously walked? The wall is one foot away. So, I walk six inches toward it." The professor does so. "But now, I can only walk half of the distance I just did. So, I move three inches closer." He does so. You lean closer, eager to hear the professor's next words.
"But how will I ever reach the wall? As I move closer and closer, the distance I can travel becomes smaller and smaller! It is impossible for me to reach this wall, even though it's so close!"
"But what if I can only walk half of the distance I have previously walked? The wall is one foot away. So, I walk six inches toward it." The professor does so. "But now, I can only walk half of the distance I just did. So, I move three inches closer." He does so. You lean closer, eager to hear the professor's next words.
"But how will I ever reach the wall? As I move closer and closer, the distance I can travel becomes smaller and smaller! It is impossible for me to reach this wall, even though it's so close!"