Answer:
"Three religions" refer to Confucianism, Buddhism and Taoism. The development of the concept of the three religions can be divided into several stages. Emperor Liang Wu in the Wei, Jin, Southern and Northern Dynasties was a stage, Tang and Song Dynasties was a stage, and Yuan, Ming and Qing Dynasties was a stage. In the initial stage, although there were three religions, they were independent of each other, of course, they had influence on each other. The reason why Confucianism, Buddhism and Taoism were mentioned in the same breath was that they emphasized the complementarity of their social functions. The middle stage is a transitional stage, which mainly lies in the circulation and integration of each other's internal consciousness, gradually becoming "you have me" and "I have you". However, as far as the mainstream is concerned, they are still different. Only in the last stage can there be a true religious form of integration of the three religions. Among them, the second stage is to add new content on the basis of continuing the complementary functions of the three religions in the first stage, and the third stage is also to evolve a new element of "three religions in one" on the basis of the first two stages, which also reflects the growing trend of the convergence of the three religions.The objective existence of the three religions in society is the basis of the emergence of the concept of the three religions, but the concept of the three religions is the result of the development and change of social consciousness. However, the emergence of the concept of Three Religions and its wide acceptance by the society were first expressed by Buddhism in the Wei, Jin, Southern and Northern Dynasties. There was no word "Three Religions" in people's writings before the Three Kingdoms. The first volume of Guanghongming Collection contains the article "The Lord of Wu, Sun Quan, discusses the three schools of Buddhism and Taoism", and mentions the three schools of Confucianism, Buddhism and Taoism. And "The Theory of Reason and Confusion" of the Northern and Southern Dynasties, on the consistency of Confucianism, Buddhism and Taoism; these can be said to be the initial consensus of the three religions ". Later, the word "Three Religions" appeared more and more frequently in the literature. During the Jin and Northern and Southern Dynasties, there was no doubt that Buddhism and Taoism were powerful social beings.The complementarities and similarities between Confucianism and Buddhism, Confucianism and Taoism, and Buddhism and Taoism at that time, there were many suggestions and discussions respectively, especially "people in the Southern Dynasty were inclined to talk about reason, so they often said that the three religions were harmonious". For example, Sun Chuo said in Yu Dao Lun: "Zhou Kong saved the worst. Buddhism knows its roots. It is the beginning and the end of the story. Ming Monk Shao believed that "the Buddha opened three generations, so the circle should be infinite; when the old stop living, the religion should be extremely pure", so "Zhou Kong and Lao Zhuang are the teachers of the emperor" and "Sakyamuni sends the true song of the poor source, which is communicated by the Mingshen Taoist". Mr. Wang Zhixin elaborated on Zhang Rong, Gu Huan and other people's thought of "Tao is the same as Qi but different": "Tao in the metaphysical aspect is originally one; only in the physical aspect, there is a difference between Buddhism and Taoism... These are the opinions of the same origin of the six dynasties and the three religions, which have a great impact on later generations". The reason for this is that the social basis on which the three religions depend and the social role they play are the same or consistent.