# Ennin

Ennin (圓仁 or 円仁, 793 CE or 794 CE – 864 CE), better known in Japan by his posthumous name, Jikaku Daishi (慈覺大師), was a priest of the Tendai school of Buddhism in Japan, and its third Zasu (座主, "Head of the Tendai Order"). Ennin was instrumental in expanding the Tendai Order's influence, and bringing back crucial training and resources from China, particularly esoteric Buddhist training and Pure Land teachings.

## Life
### Birth and origin

He was born into the Mibu (壬生) family in present-day Tochigi Prefecture, Japan and entered the Buddhist priesthood at Enryaku-ji on Mt. Hiei (Hieizan) near Kyoto at the age of 14.

### Trip to China

In 838, Ennin was in the party which accompanied Fujiwara no Tsunetsugu's diplomatic mission to the Tang dynasty Imperial court. The trip to China marked the beginning of a set of tribulations and adventures which he documented in his journal. The journal describes an account of the workings of the government of China, which saw strong and able administrative control of the state and its provinces, even at a time of a supposed decline of the Tang dynasty. His writings also expanded on religious matters and commerce. He stayed in Xi'an for five years.
Initially, he studied under two masters and then spent some time at Wutaishan (五臺山; Japanese: Godaisan), a mountain range famous for its numerous Buddhist temples in Shanxi Province in China. Here, he learned go-e nembutsu (五会念仏, "Five tone nembutsu") among other practices. Later he went to Chang'an (Japanese: Chōan), then the capital of China, where he was ordained into both mandala rituals: the Mahāvairocana-sūtra and the Vajraśekhara-sūtra, along with initiation and training in the Susiddhikara Sūtra tantra. He also wrote of his travels by ship while sailing along the Grand Canal of China.
Ennin was in China when the anti-Buddhist Emperor Wuzong of Tang took the throne in 840, and he lived through the Great Anti-Buddhist Persecution of 842–846. As a result of the persecution, he was deported from China, returning to Japan in 847.

### Return to Japan

In 847 he returned to Japan and in 854, he became the third abbot of the Tendai sect at Enryakuji, where he built buildings to store the sutras and religious instruments he brought back from China. His dedication to expanding the monastic complex and its courses of study assured the Tendai school a unique prominence in Japan. While his chief contribution was to strengthen the Tendai tantric Buddhist tradition, the Pure Land recitation practices (nenbutsu) that he introduced also helped to lay a foundation for the independent Pure Land movements of the subsequent Kamakura period (1185–1333). Ennin also founded the temple of Ryushakuji at Yamadera.

## Works

Ennin was a prolific writer, producing over one hundred works.
His diary of travels in China, Nittō Guhō Junrei Kōki (入唐求法巡礼行記), was translated into English by Professor Edwin O. Reischauer under the title Ennin's Diary: The Record of a Pilgrimage to China in Search of the Law. Sometimes ranked among the best travelogues in world literature, it is a key source of information on life in Tang China and Silla Korea and offers a rare glimpse of the Silla personality Jang Bogo.

## Thought

Ennin played a crucial role in developing the Esoteric Buddhist tradition within Japanese Tendai Buddhism, known as Taimitsu (台密). Drawing from his experiences studying in Tang China, Ennin sought to expand and refine the Esoteric teachings that Saichō had introduced but left incomplete. Central to Ennin's Esoteric metaphysics was his theory that the syllable "A", as the foundational vowel in the Sanskrit alphabet, represented the ultimate reality that is unborn and undying. This reality is equated with the inner enlightenment of the cosmic Buddha Mahāvairocana (Jp. Dainichi, 大日), the central figure in East Asian Esoteric Buddhism.
Ennin identified the syllable "A" as the scriptural essence of key Esoteric texts such as the Vajraśekhara-sūtra and the Mahāvairocana-sūtra. In his commentary on the Vajraśekhara-sūtra, he declared that the syllable "A" unified the sutra's diverse meanings. Citing the Mahāvairocana, Ennin maintained that the Esoteric teachings in their entirety are encapsulated by the syllable "A." He asserted that this syllable is the source of all phenomena, and in response to differing conditions, it manifests either as the enlightened realm symbolized by Esoteric mandalas or as the realm of delusion experienced by ordinary beings. This framework echoes Saichō's doctrine of "Suchness according with conditions," in which ultimate reality manifests itself in response to changing circumstances.
Ennin further linked the "A" syllable to the differentiated expressions of truth symbolized by the various sounds and characters in Buddhist mantras. He claimed that the single syllable "A" expands into all syllables, reflecting the principle that Suchness manifests in accordance with conditions. In the question-and-answer section of his commentary, Ennin affirmed that the Buddha's enlightened realm—depicted in the vajra realm mandala—is established through the conditioned arising of the dharma-realm, which itself embodies dharma-nature. Here, Ennin emphasized that the syllable "A" manifests in accordance with conditions to produce the phenomenal world. He further maintained that this understanding aligned with the Tendai doctrine of the Buddha-nature of insentient beings (c.f. Zhanran), reinforcing the idea that all things participate in the ultimate reality of Suchness according with conditions.