V. From Yarrow to Coins: The Decline and Evolution of Divination

The Da Yan method flourished from the Shang and Zhou dynasties through the Han. However, as history progressed, it was gradually marginalized.

1. Complexity is the Enemy

A standard Da Yan divination takes 15–20 minutes even for a fast practitioner, and up to half an hour for others. It is incredibly easy to miscount; a single error ruins the entire hexagram. For urgent battlefield decisions or marketplace divination, this was simply too slow. Consequently, after the Tang and Song dynasties, the "Huo Zhu Lin" method (Coin Oracle) rose to prominence.

2. The Price of "Sincerity"

The Da Yan method emphasizes ritual and achieving "Unity of Heaven and Man" during the long counting process. As divination became secularized and commercialized, people became more concerned with the accuracy of the result rather than the psychological cultivation of the process.

3. A Modern Perspective: Why Do We Still Need Da Yan$3

In an age where computer algorithms can generate billions of random numbers per second, does the Da Yan method still matter$4 The answer is yes.

The Wisdom of Slowness: In an era of double-speed everything, Da Yan forces us to slow down. The repeated dividing and combining of those forty-nine stalks is a process of organizing one's own thoughts. By the time you finish eighteen changes, you may already have the answer in your heart before the hexagram even appears.
Simulating Chaos Theory: As mentioned, the unique probability distribution of Da Yan is an ancient simulation of "non-linear systems" in nature. It reminds us that world development tends toward inertia (Young Yang/Ying), while sudden mutations (Old Yang/Yin), though critical, are rare.