From I Ching: The Great Treatise
The Book of Changes contains the measure of heaven and earth; therefore it enables us to comprehend the tao of heaven and earth and its order.
Looking upward we comprehend with its help the signs of the heavens, looking down we examine the lines of the earth. Thus we come to know the circumstances of dark and light. Going back to the beginning of things and pursuing them to the end, we come to know the lessons of birth and death. The union of seed and power produces all things; the escape of the soul brings about change. Through this we come to know the conditions of outgoing and returning spirits.
Since in this way man comes to resemble heaven and earth, he is not in conflict with them. His wisdom embraces all things, and his tao brings order into the whole world; therefore he does not err. He is active everywhere but does not let himself be carried away. He rejoices in heaven and has knowledge of fate, therefore he is free of care. He is content with his circumstances and genuine in his kindness, therefore he can practice love.
In it are included the forms and the scope of everything in the heavens and on earth, so that nothing escapes it. In it all things everywhere are completed, so that none is missing. Therefore by means of it we can penetrate the tao of day and night, and so understand it. Therefore the spirit is bound to no one place, not the Book of Changes to any one form.
That which lets now the yin (yielding), now the yang (firm) appear is tao.
As continuer it is good. As completer it is the essence.
The kind man discovers it and calls it kind. The wise man discovers it and calls it wise. The people use it day by day and are not aware of it, for the way of the superior man is rare.
It manifests itself in kindness but conceals its workings. It gives life to all things but it does not share the anxieties of the holy sage. Its glorious power, its great field of action, are of all things the most sublime.
It possesses everything in complete abundance: this is its great field of action. It renews everything daily: this is its glorious power.
As begetter of all begetting, it is called change.
As that which creates the primal images, it is called the Creative; as that which imitates them it is called the Receptive.
In that it serves for exploring the laws of number and thus for knowing the future, it is called revelation. In that it serves to infuse an organic coherence into the changes, it is called the work.
That aspect of it that cannot be fathomed in terms of the yang and yin is called spirit.
In a state of rest the Creative (yang) is one, and in a state of motion it is straight; therefore it creates that which is great. The Receptive (yin) is closed in a state of rest, and in a state of motion it opens; therefore it creates that which is vast.
(Chapters four and five, Richard Wilhelm translation)