A river flows, a raindrop falls, a mountain stands; each according to its nature. Our nature can sometimes be un-pure. An ideal nature is to be humble, dignified, respectful of all. The ways of the Tao can be a gentle reminder that we should seek pureness in all that we do. When we lose our nature, we become artificial and this can lead to a life filled with seeking the material. We become contaminated by that which seeks to divide us from the harmony that we can know within.