The mandate of heaven is called nature; following nature is called the Dao; cultivating the Dao is called teaching. The Dao is something that cannot be left for a moment; if it can be left, it is not the Dao. Therefore, the noble person is cautious about what is unseen and fearful of what is unheard. Nothing is more manifest than the hidden, nothing is more apparent than the subtle. Therefore, the noble person is careful in solitude. When joy, anger, sorrow, and pleasure have not yet arisen, it is called the mean. When they arise and all are in harmony, it is called harmony. The mean is the great foundation of the world, and harmony is the universal path. When the mean and harmony are achieved, heaven and earth are in their proper places, and all things are nurtured.