In the Kenkairon Saichō classified the five bodhisattvas into two major categories, those who backslid and those who did not. In the Ketsugonjitsuron Saichō further developed the classification by matching the five types of bodhisattvas with the four categories (kehō shikyō) of Chih-i’s classification of the contents of Buddhist teachings. The five types can be summarized as follows:

1. The bodhisattva who followed the practices of the sheep vehicle was equivalent to the Buddhist in the Abhidharmakośa who required over three great kalpas to attain Buddhahood.
2. The bodhisattva who followed the practices of the elephant vehicle corresponded to the practitioner of Common teachings, represented in this case by the prajn͂āpāramitā (Perfection of Wisdom) teachings.
3. The bodhisattva who followed the practices of the vehicle which endowed him with superhuman powers enabling him to reach the sun and moon corresponded to the practitioner of the fifty-two stages outlined in the Ying lo ching and thus was equivalent to one form of the Unique teaching (bekkyō).
4. The bodhisattva who followed the practices of the vehicle which endowed him with the superhuman powers of a Śrāvaka corresponded to the practitioner of another form of the Unique teaching, the follower of the forty-one stages presented in the Hua yen Ching (Avatamsakasūtra).
5. The bodhisattva who followed the practices of the vehicle which endowed him with the superhuman powers of the Buddha corresponded to the practitioner of the Perfect teaching (engyō n u). Saichō noted that this bodhisattva was like the eight-year old Nāga girl described in the Lotus Sūtra who turned into a man and immediately attained enlightenment.

Saichō died before he could further develop this classification and discuss such problems as how Esoteric Buddhism would fit into the system. However, the reasons for Saichō’s interest in this classification system are clear. It enabled him to discuss Buddhist practices in terms of the speed with which they would enable a practitioner to attain enlightenment without backsliding.