Yize the Buddhist monk was a disciple of Huizhong, the sixth patriarch of Niu-tou Zen. After Huizhong passed away, Yize moved to the grotto of Tiantai Mountain and practiced Zen for 40 years. Afterwards, he was so enlightened that he founded a doctrine widely known as the Grotto Buddhist Philosophy. The Grotto Buddhist Philosophy can he characterized as a kind of Zen that, informed by Taoism, preserves both the legacy of Grotto Buddhism and the features of Niu-tou Zen.