Esoteric Buddhism ［密教］ ( mikkyō): Also, esoteric teachings. Those Buddhist teachings that are conveyed secretly or implicitly and are held to be beyond the understanding of ordinary persons. They are defined in contrast to the exoteric teachings, or those teachings that are explicitly revealed and accessible to all. According to the True Word ( Shingon) school, the esoteric teachings are those teachings that Mahāvairochana Buddha preached secretly to Vajrasattva, who compiled them and sealed them in an iron tower in southern India. The school holds that they contain the enlightenment of Mahāvairochana Buddha, which is said to be beyond ordinary understanding.
The line of transmission of Esoteric Buddhism is held to be from Vajrasattva to Nāgārjuna, and then down through Nāgabodhi, Chin-kang-chih ( Vajrabodhi), Pu-k’ung (Amoghavajra), Hui-kuo, and finally to Kōbō, the founder of the True Word school in Japan. The school also lists eight patriarchs who upheld Esoteric Buddhism: Nāgārjuna and Nāgabodhi who spread it in India; Chin-kang-chih, Pu-k’ung, and Shan-wu-wei (Shubhakarasimha) who introduced and established it in China; I-hsing and Hui-kuo who propagated it in China; and Kōbō who brought it to Japan. Esoteric Buddhism in India was a form of Tantrism that incorporates indigenous magical and ritualistic elements such as symbolic gestures (mudras) and spells (mantras), as well as diagrams (mandalas) and the worship of numerous deities.
Shan-wu-wei, Chin-kang-chih, and Pu-k’ung introduced Esoteric Buddhism to China. Kōbō (774–835), who went to China and studied under Hui-kuo, a disciple of Pu-k’ung, brought these teachings to Japan. He systematized them as the Japanese True Word school. According to this school, the esoteric teachings are the three mysteries—the mind, mouth, and body—of Mahāvairochana Buddha. Mahāvairochana is believed to be omnipresent, constantly expounding the Law for his own enjoyment. Through the fusion of the common mortal’s three categories of action—mind, mouth, and body—with Mahāvairochana’s three mysteries, people can understand the Buddha’s teachings. Kōbō taught that, by forming mudras with one’s hands, chanting mantras with one’s mouth, and concentrating one’s mind on mandalas as objects of devotion, one could become identical with Mahāvairochana Buddha. That is, Kōbō said that the practice of the three mysteries enabled one to attain Buddhahood in one’s present form. Thus his teachings are referred to as esoteric.
Shakyamuni Buddha, on the other hand, who appeared in this world as a human being, expounded his teachings in accordance with the people’s capacity. The True Word school claims that, because these teachings were expounded explicitly within the reach of the people’s understanding, they are to be called exoteric and are inferior to the teachings of the transcendent Mahāvairochana Buddha. Esoteric teachings were also endorsed by the Tendai school. Tendai Esotericism was developed by Jikaku, the third chief priest of the Tendai school, Chishō, the fifth chief priest, and others. Unlike Kōbō’s True Word school, Tendai Esotericism holds that Shakyamuni and Mahāvairochana are two aspects of the same Buddha. Tendai Esotericism views the three vehicles as exoteric teachings, and the one vehicle as the esoteric teaching. It classifies such sutras as the Lotus and Flower Garland as one vehicle, and therefore esoteric, sutras. Because they do not mention mudras and mantras, which constitute esoteric practice, however, those sutras are called esoteric teachings in theory, while the Mahāvairochana and Diamond Crown sutras are called esoteric teachings in both theory and practice. Tendai Esotericism claims that while the Lotus and Mahāvairochana sutras are equal in terms of principle, the Mahāvairochana Sutra is superior in terms of practice.