In a letter to his friend Wang Hui王回 (1023–1065), the great Song dynasty (960–1279) politician, scholar, thinker, and writer Wang Anshi王安石 (1021–1086) makes a distinction between the golden age of the ancients and the less-than-desirable world of the present. More importantly, it claims that the golden era was marked by a commitment to unity. Not only were morality and customs of the world made the same, but the learned were united in their learnings and opinions. The periods after the golden age, on the other hand, were marked by diversity and confusion arising from how the truth is understood. Wang believed that he had found the truth about unity and how it could be achieved from reading the Classics. His ambitious political reform (called New Policies) was a grand program that sought to bring the ideal of unity to the world through government.
Wang Anshi was of course not the only major thinker in Chinese history to ponder the question of unity. In fact, a dominant and enduring theme in the history of Chinese thought is the search for unity. Faced with uncertainties arising from a diverse and complex world, thinkers in different periods and with different intellectual orientations saw it as their main mission to discover the true nature of unity and ways of realizing it for attaining a harmonious world. The process began when Confucius (551–479 bce) was confronted with the chaotic reality following the gradual collapse of the Zhou dynasty (1046–256 bce) and its institutions and cultures. It ended with the fall of the Qing dynasty (1644–1911), the last imperial regime, when new ideas of nation-state began to drastically transform the Chinese worldviews. During the two millennia in between, the search for unity spanned distinctive intellectual trends often labeled as Confucian, Daoist, or Buddhist. But such loose and often retrospective labeling cannot do justice to the complexity of history. It is therefore important to go beyond the labels and examine the common assumptions about unity among the major thinkers during a given period and how that changed over time. In doing so, we will be able to trace the emergence, development, and sometimes decline of distinctive intellectual trends before the 20th century.