The Chinese Sinocentrism

   There were many reasons for the isolation of ancient China. One such reason was because of the overriding concept of Sinocentrism, which identified China as the center of the world:

   The Sinocentric system was a hierarchical system of international relations that prevailed in East Asia before the adoption of the Westphalian system in modern times. Surrounding countries such as Japan, Korea, the Ryūkyū Kingdom, and Vietnam were regarded as vassals of China and relations between the Chinese Empire and these peoples were interpreted as tributary relationships under which these countries offered tribute (朝貢) to the Emperor of China. Areas outside the Sinocentric influence were called Huawaizhidi (化外之地), meaning "uncivilized land".
   At the center of the system stood China, ruled by the dynasty that had gained the Mandate of Heaven. This Celestial Empire (神州 Shénzhōu), distinguished by its Confucian codes of morality and propriety, regarded itself as the only civilization in the world; the Emperor of China (huangdi) was regarded as the only legitimate Emperor of the entire world.

   This passage is from Wikipedia (http://en.wikipedia.org/wiki/Sinocentrism), describing the supremacy of China. Since China had advanced more technologically, they were able to create the overriding system for what they believed was the entire world. They prided themselves as being the best, and therefore ignored any Westerners who claimed otherwise. This arrogance was a major reason that they did not allow the West to trade until the mid 19th century.