This alternation of imperial patronage in the south may have been the reason why Wên Hsüan Ti, the ruler of Northern Ch'i[639], and for the moment perhaps the most important personage in China, summoned Buddhist and Taoist priests to a discussion in 555. Both religions could not be true, he said, and one must be superfluous. After hearing the arguments of both he decided in favour of Buddhism and ordered the Taoists to become bonzes on pain of death. Only four refused and were executed. Under the short Ch'ên dynasty (557-589) the position of Buddhism continued favourable. The first Emperor, a mild and intelligent sovereign, though circumstances obliged him to put a great many people out of the way, retired to a monastery after reigning for two years. But in the north there was a temporary reaction. Wu-Ti, of the Northern Chou dynasty[640], first of all defined the precedence of the three religions as Confucianism, Taoism, Buddhism and then, in 575, prohibited the two latter, ordering temples to be destroyed and priests to return to the world. But as usual the persecution was not of long duration. Five years later Wu-Ti's son withdrew his father's edict and in 582, the founder of the Sui dynasty, gave the population permission to become monks. He may be said to have used Buddhism as his basis for restoring the unity of the Empire and in his old age he became devout. The Sui annals observe that Buddhist books had become more numerous under this dynasty than those of the Confucianists, and no less than three collections of the Tripitaka were made between 594 and 616. With the seventh century began the great T'ang dynasty (620-907). Buddhism had now been known to the rulers of China for about 550 years. It began as a religion tolerated but still regarded as exotic and not quite natural for the sons of Han. It had succeeded in establishing itself as the faith of the majority among both Tartars and Chinese. The rivalry of Taoism was only an instance of that imitation which is the sincerest flattery. Though the opposition of the mandarins assumed serious proportions whenever they could induce an Emperor to share their views, yet the hostile attitude of the Government never lasted long and was not shared by the mass of the people. It is clear that the permissions to practise Buddhism which invariably followed close on the prohibitions were a national relief. Though Buddhism tended to mingle with Taoism and other indigenous ideas, the many translations of Indian works and the increasing intercourse between Chinese and Hindus had diffused a knowledge of its true tenets and practice.