Know a strength of a man,
But keep the gentleness of a female,
Be a mountain stream of the world.
Being a mountain stream of the universe,
A constant virtue never leaves,
It will return to the softness of a baby.
Know the white,
But keep the black!
Be a model to the world!
Being a model to the world,
A constant virtue never changes,
It will return to the nothingness (infinite)
But keep humility.
Be the valley of the universe!
Being the valley of the universe,
Constant virtue is bound to be sufficient,
It will return to simplicity.
A man of simplicity is useful,
Sages (rulers) can employ him as an official,
Thus the system is perfect and needs no modification.
Baby Skyler Lin
Here Lao Tzu shows us that by keeping the softness of female with the strength of male; he can gather the people of the world like mountain streams flow down together so naturally. Similarly, keeping the black with the white and humility, he has the bosom to accept the people of the world so they will surround him naturally.
All these will bring a person back to the simplicity to become a useful vessel. Sages can use him as an officer to rule a country by following nature. Thus the system becomes perfect, and you need not modify it.