All things are divided into yin and yang. Yin is what cannot be seen, known as dark matter; yang is what the eye can see, known as visible matter.
Humans, too, are formed from yin and yang. Yin is the soul, and yang is the body.
Those with a soul but no body are spirits adrift: they drift through the world, weightless and unseen by the living.
Those with a body but no soul are walking corpses: dull and dazed, they stumble along, seeming witless to all who see them.
A person must have body and soul in balance to remain safe and sound. A weak soul brings dullness; a weak body brings illness.
When a person dies, yin and yang are sundered, and soul and body part ways. The soul can linger in the darkness for forty-nine days, while the body can remain in its coffin for eighty-one.
