During the period of Three Emperors and Five Emperors, Huangdi, known as the ancestor of the Chinese nation, put forward the idea of "the harmony of all nations". "Harmony between countries" means that there is only one country in the world and all ethnic groups are unified. Sima Qian said in Records of the Historian that the Yellow Emperor "exercised great control over all the people and valued the sum of all the people". This idea of "harmony between countries" is the basis of the unified thought of later generations.
In Shang Dynasty, Yi Yin put forward the idea of "being cautious and difficult, and being self-centered", which is the development of the Yellow Emperor's idea of "harmony but difference". In his book On Life, he clearly put forward the view that "the son of heaven is the king of all peoples".
In the Zhou Dynasty, Zhou people inherited the idea that "all nations are ruled by kings" and put forward a more explicit slogan: "Is the world the land of kings, the land of leaders, and the land of Wang Zhichen?" They believe that everything in the world should be subject to the rule of the Zhou royal family. In order to achieve this goal, the Zhou Dynasty practiced patriarchal clan system at home and enfeoffment system at abroad. During the Spring and Autumn Period, the royal family of Zhou Dynasty declined, and countries competed for hegemony, but the essence of hegemony was still to compete for or safeguard supreme sovereignty and realize the new unification of the world.
Confucianism and Mohism are the most popular theories, and there is a saying of "non-Confucianism and Jimo". Confucius advocated that "the conquest of rites and music comes from emperors" and tried to maintain the unified situation of the world returning to Zhou Dynasty. Many of his thoughts embody the idea of supremacy of kingship and political unity, and are regarded as the classic theory of world unity by later generations. In addition, the idea of "Great Harmony" put forward by Confucius, that is, "the world is public", also contains a social ideal of great unity. It can be said that Confucius and his Confucian school are pioneers who are committed to building a unified theory.
Among the Mohist theories, Shang Tong's and Monk Xian's theories also provided the ideological source for the later construction of the unified theory. Mozi believes that if everyone has his own opinion, it will be difficult to unify the world. Only when the people and the rulers are consistent and unified step by step can the world be unified to the son of heaven. Mozi's view of "Shang Tong" essentially represents the aspirations of the oppressed people, who hope to have a unified central dynasty to avoid their sudden death in the war.
Another important school in the Spring and Autumn Period was Taoism, represented by Laozi. Laozi combined the philosophical concept of "Tao" with the thought of "one" and pointed out: "The old road is big, the sky is big, the land is big, and the people's congress is big. There are four big cities in the area, one of which is inhabited. Man's law is based on the earth, the earth is based on the sky, the sky is based on the Tao, and the Tao is natural. " Laozi's political thought is to return to nature and Tao. No matter how it changes, it ultimately belongs to the "one" of "Tao".
By the Warring States period, a hundred schools of thought had a deeper understanding of reunification. The representative figure of Confucianism in this period was Mencius. When Liang asked Mencius, "Is the world evil?" At that time, Mencius said, "Book one." When Liang asked how to make the world stable, Mencius replied that only reunification can make the world stable. Mencius realized that the world will not be in an era of disputes among countries forever, and the final result will inevitably be unity.
Xunzi is a master of Confucianism and a teacher of legalists Han Fei and Li Si. He put forward the view that "there is only one family in the four seas", and thought that the world "will be combined for a long time". Only by combining Confucianism and law and combining etiquette and law can the task of unifying the world be completed.
Legalism was the darling of the Warring States period. They are designers and builders of centralized and autocratic systems. When they realized that world unification was inevitable, they didn't put forward too many empty opinions, but did a lot of real things. For example, Han Fei believes that reunification can only be achieved through war, so his main energy is concentrated on the theory of centralizing monarchical power and enriching Qiang Bing, and these theories can be truly realized. In the end, although Han Fei died, his theory was put into practice by the first emperor and Li Si, and the unification of Qin State was completed.