Scholars disagree about when the dispute over the precepts began. One scholar has suggested that Saichō may have been influenced by some of Dōchū’s disciples who, following Chien-chen’s teachings, called for a more open Buddhist order. Others have suggested that on his trips to Kyushu and Tōgoku, Saichō may have gone to see the kaidan (precepts platforms) in these two areas, and thus may have been considering reforms as early as 814. Neither of these theories has been proven.

The dispute began in earnest with Saichō’s efforts to have the court designate his monastery, Hieizanji, a Mahāyāna temple. On the seventh day of the second month of Konin 9 (late 817) Kōjō reports that Saichö told him that he wanted “to establish a Mahāyāna temple in order to propagate the (Tendai) School.” Kōjō seems to have been surprised by Saichō’s statement. According to Kōjō’s Denjutsu isshinkaimon, the following conversation took place:

The disciple (Kōjō) said, “There are no Mahāyāna temples in Japan. Why must we now suddenly establish a One-vehicle temple (ichijōji)?”

Our late teacher (Saichō) said, “I will bestow on you the title ‘One-vehicle (ichijō)’.”

His disciple (Kōjō) said, “Since there are no Mahāyāna temples in Japan yet, I will not take the One-vehicle title. Please bestow it on me after we establish a Mahāyāna temple.”

Our late teacher said, “In India there are purely Mahāyāna temples, purely Hinayāna temples and mixed (Mahāyāna and Hinayāna) temples.”

His disciple said, “If these three types of temples exist, then I ought to take the title. Temples are, after all, only places where monks reside.”

At this time, no mention was made of precepts. Exactly what the term ‘Mahāyāna temple’ or ‘One-vehicle temple’ designated and how such an institution would differ from the temples in Japan at that time is not specified in the conversation. Probably it was the beginning of an attempt by Saichō to develop a monastic institution which would embody, in a practical way, the issues being debated with Tokuitsu. If the court had recognized Saichō’s claim that Hieizanji was a Mahāyāna temple, it certainly would have enhanced the reputation of the Tendai School at the expense of the Hossō and Sanron schools by implying that they did not have purely Mahāyāna temples.