One should observe nine norms when studying Dao:
The study and cultivation of Dao does not merely aim at understanding the general idea of Dao. What is more important is to practice what Dao advocates. This requires people to observe some basic norms. The Seven Slips of a Cloudy Satchel puts forward nine principles that must be observed.
Firstly, keep to harmony: Everything under heaven connotes Yin and Yang. The vital breaths of Yin and Yang keep acting upon each other, and thus things keep unifying themselves. Sages4 follow the laws of Heaven and Earth. They are not confined to common customs or common people. "It is most important to keep to harmony".
Secondly, keep to the spirit: This means to guard one's spirit and prevent it from chasing external things and getting exhausted.
Thirdly, keep to the Vital Breath: Blood and the Vital Breath5 are the essence of human beings. Filled with the Vital Breath, human beings won't be invaded by calamities or harmful breath. When one is tied down by desires, his spirit will be exhausted and his inner Vital Breath will consequently be insufficient. He who cultivates Dao must purify his heart, reduce his desires and protect and nourish his Original Vital Breath6.
Fourthly, keep to benevolence: Fearless of the threat of death, righteous people can be moved by benevolence, but cannot be compelled by force. Those who cultivate Dao regard the human world as unimportant, so they are not tied up; regarding all things as trivial, they will not be perplexed; regarding life and death equally, they are fearless; indifferent to changes, they are wise and won't be dazzled. They are more able to keep to benevolence than common righteous people are.
Fifthly, keep to simplicity: One should get rid of filth and worries, and understand the way of balance and harmony in Nourishing one's Life7. As for food, it's sufficient to allay one's hunger, and as for clothing, it's adequate to cover the body and keep out the cold. One should never be greedy. Simplicity can certainly be achieved if one doesn't exercise his wits too much.
Sixthly, keep to constancy: It is inevitable that people become powerful, lowly, poor or rich, but those who have secured Dao will not change their original intention no matter how their conditions change.
Seventhly, keep to pureness: One should have his mind as pure as water, and have no greedy or filthy ideas, and shouldn't indulge in his desires.
Eighthly, keep to fullness: The sun and moon will begin to wane when they reach the full. One shouldn't attempt to be perfect, but should never be self-satisfied. He must increase his virtues every day, and not dare to be violent.
Ninthly, keep to gentleness: Only being gentle can conform to the way of simplicity. To be specific, one should have no happiness, anger, joy or bitterness, regard all things as mysteriously identical, and make no distinction between right and wrong, harmonize and soften his Vital Breath, and balance his body so as to drift along with Dao.