The ancients say that Tao can be vast and can be minute and so profound that only the right persons can penetrate all its mysteries. They proffered similar references to the Book of Changes (I Ching / Yijing) in the Great Treatise.
Just like the pursuit of Tao, brilliant minds and the literati down the millennia try to penetrate the mysteries of the Yi. How many were actually successful is difficult to tell since there are few written records left behind for posterity. As a comparison, the Daoists keep Rolls of those successful in attaining the Tao (after penetrating its mysteries) to become celestial immortals and whom invariably can be authenticated in the temples, if required.
Of the Yi, the ancients and the wise left behind references in the Book of History, the Zuo Zhuan (Tso Chuan) and the Ten Wings. So did Confucius and his students in the Confucian books. More than five centuries later, a whiz kid by the name of Wang Bi seemed to be able to penetrate its mysteries and recorded down his understanding that the Yi was a book of wisdom.
Several centuries had lapsed before the time of the so called Neo Daoists and Neo Confucians where brilliant minds again penetrated the mysteries of the Tao and the Yi. Chen Tuan produced many diagrams related to both studies including the Wujitu (Chart of the Infinite). Chou Dunyi produced the Taijitu (Chart of the Supreme Ultimate). From the writings of Chen Tuan, Shao Yong came up with his own diagrams and another method of divination, the Plum Blossoms Yi Number. Chu Hsi recorded down his understanding that the Yi was originally a book for divination.
It was also during this time that renowned Daoists like Chen Tuan, Lu Dongbin, and Wang Chungyang – the founder of Quanzhen - proffered their deep insights that neidan (inner alchemy) and not weidan (outer alchemy) is the method to penetrate the mysteries to attain Tao. They also advocated the integrated studies of the three doctrines – Daoist, Confucian and Buddhist for students to better understand Tao.
The profoundness and mysteries of both Tao and the Yi remain challenges down to this day. Brilliant minds and the literati still try to figure them out just like the ancients and all the wise down the ages.
Laozi and Confucius were no different; they had studied and knew the Yi well. (Remember the Book of Changes is an ancient classic.) Well enough to refer to the Yi in their thoughts and writings and yet keep their meanings hidden for the right persons to discover the truths.
Yet some modern scholars, even if they have brilliant minds, tend to think that the Yi is not profound and they have had penetrated its many mysteries. Some had claimed the same about Tao.
Despite their claims, it is difficult to find their penetrating clarity requisite for an in-depth understanding of the Tao and/or the Yi.
Did anyone note that a court historiographer (a professional diviner or expert) wrongly interpreted the prognostication in the Zuo Zhuan during the Chun Chiu era? If the Tao and the Yi is not other than profound would Laozi state so in the Tao Te Ching and would Confucius in his old age request for fifty years (as recorded in his Analects) to study the Book of Changes so that he would not come to great faults?
If a great sage himself needed so much time to study the Yi, would he tell his students to study this ancient classic to correct their faults? Was it not proper for Confucius to request them and his son to study the easier-to-understand Book of Odes or the Book of Music instead? (This is written in response to spurious claims that Confucius did not study or refer to the Yi in his dealings with his students.)
As a matter of interest, how many Yi scholars out there can really say that they understand Confucius’s interpretations of the lines or hexagrams in the Book of Changes as he did?
If they know little about Confucian doctrines, they may not quite understand where Confucius was coming from.
And if they know any less about ancient Chinese history, they could be clueless as to what Laozi and Confucius meant when they talked about the closure of Heaven and Earth - and therefore the absence of Tao – in their respective texts while making an inference to the Yi.
Meanwhile less brilliant students like us should put more effort into reading the correct books and do homework on Tao and the Yi. It is also proper to discuss our learning with likeminded fellows.