Yin and Yang in your pillars
Picture a hill on a sunny afternoon. One side is in full light, the other in shade. It's the same hill. That's the oldest picture behind Yin and Yang (陰陽, ): two sides of one thing, not two enemies.
Two ways of moving
- Yang goes out. It starts, opens, pushes and shows. Think of noon, summer, a voice raised to call someone in from the garden.
- Yin comes back. It gathers, keeps, finishes and protects. Think of night, winter, a voice lowered so the baby can sleep.
Neither is worth more than the other. A day needs both, and so does a person. A Yang character isn't "stronger" and a Yin one isn't "weaker". They just go about things differently.
Every character has one
In BaZi, each of the ten stems and each of the twelve branches is either Yang or Yin. They take turns, like footsteps: first Yang, then Yin.
- Stems: 甲 is Yang Wood, 乙 is Yin Wood, 丙 is Yang Fire, 丁 is Yin Fire, and so on through Earth, Metal and Water.
- Branches: the Rat is Yang, the Ox is Yin, the Tiger is Yang, the Rabbit is Yin, and so on around the twelve animals.
So every element shows up twice among the stems, once open and once gathered. Yang Wood is the tall tree. Yin Wood is the vine that finds its way around it. Same element, different temper.
Why there are sixty pillars, not 120
A pillar always pairs like with like: a Yang stem sits on a Yang branch, and a Yin stem on a Yin branch. Ten stems and twelve branches could make 120 pairs, but only half of them ever happen. Those sixty are the cycle the calendar has repeated, in order, for thousands of years.
You'll bump into this rule in the app. When you pick a pillar in the People filters, it reminds you that a stem and a branch only pair up when both are Yang or both are Yin.
Where you'll see it
- Your Day Master. On the Chart tab, the line under your Day Master reads something like "You're Yang Water: a river" or "You're Yin Fire: a candle". That first word is your polarity.
- The ten roles. They come in pairs: Peer and Rival, Creativity and Bold expression, and so on. Both roles in a pair share an element. What tells them apart is whether the character has your polarity or the other one.
- The five elements on Today. When you tap an element in the cycle, the app reminds you that one of the two roles in that group shares your polarity and the other doesn't.
- Your ten-year cycles. Whether your decades run forward or backward through the sixty pillars depends on two things: the polarity of your Year stem, and the traditional formula (Male or Female) chosen in the birth details. A Yang year with the Male formula, or a Yin year with the Female one, runs forward. The other two run backward.
A small twist inside four branches
Every branch carries stems inside it, called hidden stems. In four of them, the main stem inside has the opposite polarity to the branch itself. The Rat is Yang, but its heart is 癸, Yin Water. The Horse is Yang and holds 丁, Yin Fire. The Pig and the Snake go the other way: Yin outside, a Yang stem inside. When the app works out a branch's role, it reads the stem inside. So if your Day Master is 壬, Yang Water, a Rat in your chart reads as Rival, not Peer, because the Water inside it is Yin.
In plain words
Yin and Yang don't say whether something is good or bad. They say how it moves: outward or inward, starting or keeping. A chart with lots of Yang may tend to feel on the go. One with lots of Yin may tend to feel more inward and steady. Both are whole, and most charts carry plenty of each.