Kaidan (Ordination Platform) (戒壇)
The term kaidan (ordination platform) is a Buddhist term that refers to a place for giving the precepts of Buddhism.
Kaidan is a place where a person who intends to become a Buddhist priest or priestess is given the precepts of Buddhism, the bounds of which are kept fixed. Such a person needs to be given the precepts of Buddhism to be duly authorized as a Buddhist priest or priestess.
Buddhism was introduced into Japan in 538, and the precepts introduced at that time were imperfect. In those days, Buddhist priests were exempted from taxation, and therefore there were many people who took the tonsure but did not enter the Buddhist priesthood (illegally ordained priests) to evade taxes. In other words, there were many corrupt priests who did not even train themselves in Buddhist ascetic practices. In response to this situation, Jianzhen was invited from Tang to introduce the precepts of Buddhism. Thereafter, only persons who could observe those precepts were authorized as Buddhist priests. Consequently, disciplines came to be observed in Buddhist society. Jianzhen had kaidan built at Todai-ji Temple in 754, and gave the precepts of Buddhism to 430 people including the Emperor Shomu in April of the same year. This is the oldest kaidan. Thereafter, Jianzhen had a building to house Kaidanin at Todai-ji Temple, and had kaidan at Kanzeon-ji Temple in Dazaifu in Tsukushi Province and Yakushi-ji Temple in Shimotsuke Province (present Shimotsuke City, Tochigi Prefecture) (Three Major Kaidan in Japan).
Since then, it has been mandatory to be given the precepts of Buddhism at one of the three kaidan mentioned above and have kaicho (a certificate to that effect) issued, and priests have been under the supervision of the State (provincial monastery). After the death of Saicho in 822, however, Imperial sanction for the construction of kaidan at Enryaku-ji Temple was given, and kaidan was built there. This is called Daijo kaidan (a Mahayana ordination platform) in some cases. In those days, the Buddhist society in China did not approve the Daijo kaidan at Enryaku-ji Temple, and the priests who had been given the precepts of Buddhism at that temple were not recognized as priests in China. In addition, Todai-ji Temple and other temples in Nanto (Nara) had antipathy toward the sanction for the construction of kaidan at Enryaku-ji Temple, which was not kanji (state-sponsored temples). This became one of the causes of the conflict between Enryaku-ji Temple and temples in Nanto.
The Daijo kaidan also caused power struggles, among which one between Sanmon (referring to Enryaku-ji Temple) and Jimon (referring to Onjo-ji Temple) of the Tendai Sect is well-known. In addition, among the priests who had been given the precepts of Buddhism at kaidan, more of them did not even train themselves in Buddhist ascetic practices and corrupted. Eison, in the Kamakura period, was originally belonged to the Shingon Sect, but later learned the doctrines of the Ritsu Sect introduced by Jianzhen to found the Shingon Ritsu Sect by combining the doctrines of both sects. He criticized the three major kaidan and the one at Enryaku-ji Temple for being no longer what they should be and being unworthy as a place to give the precepts of Buddhism, and advocated that the giving of the Buddhist precepts be effected by fixing the bounds of a sacred place to give those precepts in conformity with the precepts and performing a rite in accordance with proper procedure. He gave the Buddhist precepts at Todai-ji Temple in person again in collaboration with other like-minded priests, and also founded an original kaidan at Saidai-ji Temple (Nara City). Following this, Enkan, who had served as a priest at Enryaku-ji Temple on Mt. Hiei, left there to place an original kaidan. Thereafter, in the Kamakura New Buddhism, which was founded as a result of the conflict with temples in Nanto and Enryaku-ji Temple, original rites for entrance into the Buddhist priesthood and giving the precepts of Buddhism came to be performed. On the other hand, the kaidan at Todai-ji and Enryaku-ji Temples were respected as time-honored ones, and the precepts of Buddhism were given there until the end of the Edo period.