In Chapter IV of the Ketsujō ōjō shū 決定往生集, Chingai 珍海 lists two causes （種子 bīja） for determining jōdo ōjō or rebirth in the Pure Land, namely chūdō busshō 中道仏性 and shukuzen 宿善. Concerning the first, it is said that deliverance is possible by means of shōin 正因, true causes, which is chūdō busshō based on Sanron 三論 doctrine, and en 縁, causal conditions, such as listening to sūtras and giving rise to the aspiration to awakening （bodhicitta）. It’s also stated that it is possible to obtain rebirth in the Pure Land because of this theory of attaining Buddhahood. I think that what is described here as shōin refers to the buddha-nature of direct cause 正因仏性 explained by Jizang 吉蔵, and that en refers to the buddha-nature of indirect causes 縁因仏性, likewise explained by him. However, the simple description in the Ketsujō ōjō shū does not give a deep understanding of these relationships.
Therefore, through careful reading of the Sanron gensho mongiyō 三論玄疏文義要 and Sanron myōkyōshō 三論名教抄, which were also written by Chingai, I would like to consider its significance in rebirth in the Pure Land, clarifing the relationship between chūdō busshō and direct and indirect causes.
