Duke Ching of Qi once asked Zigong how Confucius was to be ranked as a sage, and he replied, "I do not know. I have all my life had the sky over my head, but I do not know its height, and the earth under my feet, but I do not know its thickness. In my serving of Confucius, I am like a thirsty man who goes with his pitcher to the river, and there he drinks his fill, without knowing the river's depth."