There are the high tides that flow in and low tides that flow out that allow for much and destroy much. Look to the sky and see how the moon waxes and wanes and all is natural. A sun rises and sets and rises and sets and rises and sets. One part of the world is plunged into darkness and another is bathed in light. The sage notices that there is a theme here. What was once created is then destroyed and goes back to whence it came. That which fades away manifests itself once again under the power of the Dao.