Many followed the teachings of Buddha and prominent monks such as Dahui Zonggao (1089–1163) and Wuzhun Shifan (1178–1249). However, there were also many critics of Buddhism's religious and philosophical tenets. This included the ardent nativist, scholar, and statesman Ouyang Xiu, who called Buddhism a "curse" upon China, an alien tradition that infiltrated the native beliefs of his country while at its weakest during the Southern and Northern Dynasties (420–581). The contention over Buddhism was at times a divisive issue within the gentry class and even within families. For example, the historian Zeng Gong lamented over the success of Buddhism, viewing it as a competing ideology with 'the Way of the Sages' of Confucianism, yet on his death in 1083 was buried in a Buddhist temple that his grandfather had helped build and that his brother Zeng Bu was able to declare as a private Merit Cloister for the family. Although conservative proponents of native Confucianism were highly skeptical of the teachings of Buddhism and often sought to distance themselves from it, others used Buddhist teachings to bolster their own Confucian philosophy. The Neo-Confucian philosophers and brothers Cheng Hao and Cheng Yi of the 11th century sought philosophical explanations for the workings of principle (li) and vital energy (qi) in nature, responding to the notions of highly complex metaphysics in popular Buddhist thought. Neo-Confucian scholars also sought to borrow the Mahayana Buddhist ideal of self-sacrifice, welfare, and charity embodied in the bodhisattva. Seeking to replace the Buddhist monastery's once prominent role in societal welfare and charity, supporters of Neo-Confucianism converted this ideal into practical measures of state-sponsored support for the poor under a secular mission of ethical universalism.