In March 1839, Charles Elliot, the British superintendent of trade, wrote a letter to Lin Zexu, the Qing commissioner on opium trade, regarding the trade issues between the two countries. In this letter, he referred Britain and China as "two countries." This angered the commissioner so much that he returned the letter, saying "no place under heaven can be referred to as equal to our celestial empire."

Zheng Wang wrote (in Chapter 3) that "Lin's response should also be understood from the Chinese unique tianxia (all-under-heaven) worldview." According to Wang, what were the four points of China's worldview? (Without plagiarizing, write 500 words please)