History of Yin and Yang

The concepts of Yin and Yang appeared around 700 BCE. They were recorded in the I Ching, the Book of Changes. The symbols representing Yin and Yang were a broken line (Yin) and an unbroken line (Yang).

Later, another line was added. This was called the Yin-Yang diagram. By adding multiple lines, one could indicate full Yin, full Yang, and the intermediate stages.

This theory from the I Ching became more and more refined, allowing people to capture the world around them within this concept.