The Original I Ching
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䷚ · probability of the oracle

Coins against yarrow stalks

The hidden probabilities of the oracle

Choose how many readings to simulate and compare coins against yarrow stalks bar by bar.

To consult the oracle you have to generate six lines, each in one of four states: young yang or young yin (static) and old yang or old yin (moving). The three coins give a symmetric distribution; the ancient method of the 49 yarrow stalks does not. The question: where does it show?

Three coins
9 · old yang
2/16
8 · young yin
6/16
7 · young yang
6/16
6 · old yin
2/16

● = moving state · faint bar = static line

Yarrow (49 stalks)
9 · old yang
3/16
8 · young yin
7/16
7 · young yang
5/16
6 · old yin
1/16

● = moving state · faint bar = static line

Where do the sixteenths of the yarrow come from? The experiment the ritual of the 49 stalks derives them step by step, with exact fractions.

What matches and what does not (exact)
QuantityThree coinsYarrow (49 stalks)Verdict
P(present line = yang)1/21/2identical
P(line moves)1/41/4identical
expected yang lines (present)3.003.00identical
among moving lines, share of old yang50%75%different
expected yang lines (future)3.002.25◆ different

The present hexagram comes out identical in both methods: each line is yang with probability 1/2, so the 64 hexagrams are equiprobable. And the rate of change matches too: 1/4 per line. The yarrow only breaks the symmetry in the direction of the change: a moving line is 3 times more likely to be yang-falling-to-yin. Measurable consequence: the future hexagram leans towards yin (2.25 yang lines against 3.00).

Live simulation