How do you think this old man？ This story happened in ancient China. A clever young man was making a journey. One day, when he passed by a place named HANYIN, he found an old man was watering his vegetable field. There is a well beside the field and there are some steps from the ground to the bottom of the well. This old man carried a jar, walked step by step to the bottom of the well, filled the jar, then walked back to the ground, poured the water from the jar to his field. The young man laughed at the old man. He said:" How inefficient you are. I can make a machine for you, the efficiency will be ten times than yours." The old man looked at the youg man seriously and said:" No, I am pleased with what I am doing, my vegetables which I plant are enough for me to eat. I needn't to use a machine. My teacher had told me, if a man always think to make some machines, his heart will be scheming and not be pure anymore. That's not what I wanted."