He who attains to the highest teh of simplicity and sincerity, may be compared to the ingenuousness of an infant. Poisonous insects do not sting their own young, wild beasts do not attack their own cubs, nor do birds of prey. A baby's bones may be weak and its muscles soft, but its spiritual vitality is perfect. An infant does not know about the relation of the sexes, but gradually its generative vigor will develop. Its spirit is virile, indeed! It may sob and cry all day but will not become hoarse. His unity as a child is perfect.
To understand how to preserve this unity and soundness, one must return to his original state of simplicity. To know how to return to one's original state is to be enlightened. To increase one's natural vigor means blessedness. To control one's breathing means strength. Things that are fully grown begin to decay, for growth is contrary to the principle of TAO. Things that are contrary to TAO soon pass away.