Wang Pi traced his intellectual heritage to Ching-chou. He was once a minister in the Wei government and wrote commentaries on both the Book of Changes and the Lao Tzu, that on the latter being the oldest in existence. Before he died at the early age of twenty-four, he had already inaugurated a new movement, for he raised the level of Chinese thought to that of metaphysics. Han thought was primarily concerned with cosmology and cosmogony, but Wang Pi went beyond the realms of names and forms to ultimate reality, namely, original non-being (pen-wu). According to his theory, which is developed in his commentary on the Lao Tzu, original non-being transcends all distinctions and descriptions. It is the pure being, original substance (pen-t'i), and the one in which substance and function are identified. It is whole and strong. And it is always correct because it is in accord with principle. This emphasis on principle is very conspicuous in his commentaries. Where Lao T= had destiny (ming, fate), Wang Pi would substitute principle, thus anticipating the Neo-Confucianists, who preferred to speak of the Principle of Nature (T'ien-li) instead of destiny decreed by Heaven (T'ien-ming).
The idea that there is the one underlying and uniting all phenomena is also vigorously stressed in his essay on the Book of Changes.8 This book, consisting of hexagrams made up of six broken lines (representing yin or passive cosmic force) and unbroken lines (representing yang or active cosmic force), was used in ancient times for divination but later used by Confucianists to discern principles underlying events. It had been the custom to equate each of the sixty-four hexagrams with a particular object, but Wang argues that this is unnecessary because there is a general principle behind all particular objects. This principle is discoverable in one of the six lines, so that the other five become secondary. In short, he, stresses the overall principle which unites and commands all particular concepts and events. It is remarkable that in a time of disunity and confusion he should insist on a united system based on one fundamental reality, original non-being.
However, Kuo Hsiang and Wang Pi are similar in that both consider that the sage rises above all distinctions and contradictions. He remains in the midst of human affairs although he accomplishes things by taking no unnatural action. But he is not someone who "folds his arms and sits in silence in the midst of some mountain forest." To such a sage, all transformations are the same and in dealing with things he has "no deliberate mind of his own" (wu-hsin) but responds to them spontaneously without any discrimination. Confucius, and not Lao Tzu or, Chuang Tzu, was such a sage.
In their philosophy of life, Kuo Hsiang differed greatly from Wang Pi in one respect. Kuo was a fatalist while Wang was not. Since according to Kuo everything has its own nature and ultimate principle, everything is determined and correct. Therefore he taught contentment in whatever situation one may find himself. Neither free will nor choice has meaning in his system.
Source : Wing-Tsit Chan, in Chinese Philosophy