This paper attempts to make a critical analysis of the nature of mind in the Awakening of Mahayana Faith, a text belonging to the corpus of Tathāgatagarbha literature.The first section examines the two aspects of the One Mind: the Gate of Suchness and the Gate of Samsara. The important point that the One Mind theory makes is that the purity, or suchness of the mind inherently exists, while the elements of impurity, or samsara in the mind are adventitious. The second section deals with the theoretical difficulties arising from the theory of One Mind. First, is the inherently pure mind a from of monism? Second, since the One Mind is originally pure, where does evil come from? The doctrine of śūnyatā can be employed to solve the first problem, while the theory of avidya is used to explain away the second problem. Syncretizing the theory of human nature in Yogācāra and Tathāgatagarbha traditions, the Awakening of Mahayana Faith, based on the existence of innate pure mind, established the foundation of Buddhahood.