Chinese cosmology · Concept
Yin and Yang (陰陽) are not two substances, but two directions of a single movement. Yang is what expands, heats, rises, initiates; Yin is what gathers, cools, descends, receives. The meaning of the pair is in the relation — and that is why nothing is Yin or Yang in itself, only in comparison with something else.
The ideograms carry the original image: 陽 is the sunlit slope of the hill, 陰 the shaded slope. Same hill, same instant — what changes is the side. Take away the hill and the pair dissolves: there is no shade without light to cast it.
This is the point most often missed. Yin and Yang are not good and evil, nor male and female, nor spirit and matter. They are a way of describing any pair of complementary tendencies, whatever the domain.
Water is Yin next to fire, and Yang next to ice. A pause is Yin inside a conversation, and Yang inside a silence. The classification is always relative to the term it is compared with — which is what keeps the pair from becoming a moral catalogue of things.
And each carries the seed of the other: what expands to the limit begins to contract; what accumulates to the limit begins to spill. The pair is not a static balance but a cycle, and this is the axis of the whole Chinese cosmology.
The I Ching turns this pair into notation. A solid line (⚊) writes Yang; a broken line (⚋) writes Yin. Stacking three gives a trigram; stacking six gives one of the 64 hexagrams.
The decisive part is the changing line: a line at the limit of its own tendency, about to turn into its opposite. That is where the book stops describing a state and starts describing a passage — and it is what makes the I Ching a book of changes rather than a book of types.