The natural world and the world of man are based on the very same natural laws. The Supreme Ultimate -- the fountainhead of all of these natural laws -- thus rules both the principles within the mind and heart of man, and the principles that operate within the natural world and human society, outside of our minds. This is "the Way of Nature.
While human beings are born, live, and give birth to other human beings, they must conform with the order of Nature that runs through human society and the natural world. While human beings help other human and non-human beings to live and flourish, they must lead them also to conform with the order of Nature that runs through human society and the natural world. This is "the Way of man."
For people to be able to assist in the transforming and nourishing process of heaven and earth, they must preserve and nourish their own true original nature within. At the same time, they must investigate the principles that exist within external things and affairs. When they are able to comprehend the unity of the principles of the external world and the principles within their own hearts, they will achieve personal realization of the fact that the Supreme Ultimate unites the world of nature and the world of man, and they will be transformed in perfect accord with the transformative power of heaven and earth.