Tendai (天台宗, Tendai-shū) is a Mahayana Buddhist school established in Japan in the year 806 by the monk named Saichō, posthumously known as Dengyō Daishi. The Tendai school rose to prominence during the Heian period (794-1185), gradually eclipsing the powerful Yogācāra school (Hossō-shū) and competing with the upcoming Shingon Buddhism to become the most influential at the Imperial court.

However, political entanglements during the Genpei War (1180–1185) led many disaffected monks to leave, and in some cases to establish their own schools of Buddhism such as Jōdo-shū, Nichiren-shū and the Sōtō school of Zen. Destruction of the head temple of Mount Hiei by warlord Oda Nobunaga, as well as the geographic shift of the capital away from Kyoto to Edo, further weakened Tendai's influence.

In Chinese and Japanese, its name is identical to Tiantai, its parent school of Chinese Buddhism; both Tiantai and Tendai hold the Lotus Sutra as the ultimate teaching of the Buddha and revere the teachings of Tiantai's founder Zhiyi. In English, the Japanese romanization distinguishes the particularly Japanese history of the school and its innovations. These include an exclusive use of the Bodhisattva Precepts for ordination, an emphasis on the "Four Integrated Schools", and Saichō's focus on the "One Vehicle" teaching.

David W. Chappell frames the relevance of Tendai for a universal Buddhism:[1]

Although Tendai (Chin., T'ien-t'ai) has the reputation of being a major denomination in Japanese history, and the most comprehensive and diversified school of Chinese Buddhism, it is almost unknown in the West. This meagre presence is in marked contrast to the vision of the founder of the movement in China, T'ien-t'ai Chih-i (538–597), who provided a religious framework which seemed suited to adapt to other cultures, to evolve new practices, and to universalize Buddhism.

Although Jianzhen (Jp. Ganjin) had brough Tiantai teachings to Japan as early as 754,[2] its teachings did not take root until generations later when Saichō, a monk, joined the Japanese missions to Imperial China in 804. The future founder of Shingon Buddhism, Kūkai, also traveled on the same mission; however, the two were on separate ships and never saw one another once they arrived in China.

From the city of Ningbo (then called Míngzhōu 明州), Saichō was introduced by the governor to Dàosuì (道邃), who was the seventh Tiantai patriarch, and later he journeyed to Tiantai Mountain for further study.[3] After receiving initiations in Chan and Chinese Esoteric traditions at Tiantai Mountain, Saichō devoted much of his time to making accurate copies of Tiantai texts and studying under Dàosuì. By the sixth month of 805, Saicho had returned to Japan along with the official mission to China.

Because of the Imperial Court's interest in Tiantai as well as esoteric Buddhism, Saichō quickly rose in prominence upon his return. He was asked by Emperor Kanmu to perform various esoteric rituals, and Saichō also sought recognition from the Emperor for a new, independent school of Tiantai in Japan. Because the emperor sought to reduce the power of the Hossō school, he granted this request, but with the stipulation that the new "Tendai" school would have two programs: one for esoteric Buddhism and one for meditation. However, Emperor Kanmu died shortly thereafter, and Saichō was not allocated any ordinands until 809 with the reign of Emperor Saga.

Saichō's choice of establishing his community at Mount Hiei also proved fortuitous because it was located to the northeast of the new capital of Kyoto and thus was auspicious in terms of Chinese geomancy as the city's protector.[4]

The remainder of Saichō's life was spent in heated debates with notable Hossō figures, particularly Tokuitsu, and maintaining an increasingly strained relationship with Kūkai to broaden his understanding of esoteric Buddhism.

Finally, Saichō's efforts were also devoted to developing a "Mahayana-only" ordination platform that required the Bodhisattva Precepts of the Brahmajala Sutra only, and not the pratimokṣa code of the Dharmaguptaka vinaya, which was traditionally used in East Asian Buddhist monasticism. By the time that Saichō died in 822, his yearly petition was finally granted and the traditional "Four Part Vinaya" (Chinese: 四分律) was replaced by the Bodhisattva Precepts for the Tendai.

Seven days after Saichō died, the Imperial Court granted permission for the Tendai to exclusively use the Bodhisattva Precepts for its ordination process. This effectively allowed Tendai to use an ordination platform separate from the powerful schools in Nara. Gishin, Saichō's disciple and the first zasu (座主, "Head of the Tendai Order"), presided over the first allotted ordinands in 827.[citation needed]

Further, the Tendai order underwent efforts to deepen its understanding of teachings that Saichō had brought back, particularly esoteric Buddhism. Saichō had only received initiation in the Diamond Realm Mandala, and since the rival Shingon school under Kūkai had received deeper training, early Tendai monks felt it necessary to return to China for further initiation and instruction. Saichō's disciple Ennin went to China in 838 and returned ten years later with a more thorough understanding of esoteric, Pure Land, and Tiantai teachings.[5]

By 864, Tendai monks were now appointed to the powerful sōgō (僧綱, "Office of Monastic Affairs") with the naming of An'e (安慧) as the provisional vinaya master. Other examples include Enchin's appointment to the Office of Monastic Affairs in 883. While Saichō had opposed the Office during his lifetime, within a few generations disciples were now gifted with positions in the Office by the Imperial Family. By this time, Japanese Buddhism was dominated by the Tendai school to a much greater degree than Chinese Buddhism was by its forebearer, the Tiantai.

For reference, the first eight zasu (座主, "Head of the Tendai Order") after Saichō were:[5]

Appointments as zasu typically only lasted a few years, thus among the same generation of disciples, a number could be appointed zasu in one's lifetime.

Philosophically, the Tendai school did not deviate substantially from the beliefs that had been created by the Tiantai school in China. However, what Saichō transmitted from China was not exclusively Tiantai, but also included Zen (禪), the esoteric Mikkyō (密教), and Vinaya School (戒律) elements. The tendency to include a range of teachings became more marked in the doctrines of Saichō's successors, such as Ennin (圓仁) and Enchin (圓珍). However, in later years, this range of teachings began to form sub-schools within Tendai Buddhism. By the time of Ryōgen, there were two distinct groups on Mt. Hiei, the Jimon and Sanmon: the Sammon-ha "Mountain Group" (山門派) followed Ennin and the Jimon-ha "Temple Group" (寺門派) followed Enchin.

Although the Tendai sect flourished under the patronage of the Imperial House of Japan and the noble classes, by the end of the Heian, it experienced an increasing breakdown in monastic discipline, plus political entanglements with rival factions of the Genpei War, namely the Taira and Minamoto clans. Due to its patronage and growing popularity among the upper classes, the Tendai sect became not only respected, but also politically and even militarily powerful, with major temples each fielding their own monastic armies of sōhei (warrior-monks). This was not unusual for major temples at the time, as rival schools also fielded armies, such as the head temple of the Yogācāra school, Kōfuku-ji. With the outbreak of the Genpei War, Tendai temples even fought one another, such as Mount Hiei clashing with Mii-dera depending on their political affiliations.

A number of low-ranking monks of the Tendai became dissatisfied and sought to establish independent schools of their own. Such founders as Nichiren, Hōnen, Shinran, Eisai and Dōgen—all famous thinkers in non-Tendai schools of Japanese Buddhism—were all initially trained as Tendai monks. Tendai practices and monastic organization were adopted to some degree or another by each of these new schools, but one common feature of each school was a more narrowly-focused set of practices (e.g. zazen for Zen, nembutsu for Pure Land schools, etc) in contrast to the more integrated approach of the Tendai.

Although a number of breakaway schools rose during the Kamakura period, the Tendai school used its patronage to try to oppose the growth of these rival factions—particularly Nichiren Buddhism, which began to grow in power among the merchant middle class, and Pure Land Buddhism, which eventually came to claim the loyalty of many of the poorer classes. Enryaku-ji, the temple complex on Mount Hiei, became a sprawling center of power, attended not only by ascetic monks, but also by brigades of sōhei who fought in the temple's interest. As a result, in 1571 Enryaku-ji was razed by Oda Nobunaga as part of his campaign to unify Japan. Nobunaga regarded the Mount Hiei monks as a potential threat or rival, as they could employ religious claims to attempt to rally the populace to their side. The temple complex was later rebuilt, and continues to serve as the head Tendai temple today.

The first characteristic of the Japanese Tendai school is its advocacy of a comprehensive Buddhism, ... the idea that all the teachings of the Buddha are ultimately without contradiction and can be unified in one comprehensive and perfect system. Chih-i, founder of T'ien-t'ai philosophy and practice, attempted this synthesis on the basis of the ekayāna doctrine of the Lotus Sutra.[6]

Tendai Buddhism has several philosophical insights which allow for the reconciliation of Buddhist doctrine with aspects of Japanese culture such as Shinto and traditional aesthetics. It is rooted in the idea, fundamental to Mahayana Buddhism, that Buddha-hood, the capability to attain enlightenment, is intrinsic in all things. Also central to Mahayana is the notion that the phenomenal world, the world of our experiences, fundamentally is an expression of the Buddhist law (Dharma). This notion poses the problem of how we come to have many differentiated experiences. Tendai Buddhism claims that each and every sense phenomenon just as it is is the expression of Dharma. For Tendai, the ultimate expression of Dharma is the Lotus Sutra. Therefore, the fleeting nature of all sense experiences consists in the Buddha's preaching of the doctrine of Lotus Sutra. The existence and experience of all unenlightened beings is fundamentally equivalent and undistinguishable from the teachings of the Lotus Sutra.

Tendai Buddhism, in keeping with Tiantai, reveres the Lotus Sutra as the highest teaching in Buddhism. In Saichō's writings, he frequently used the terminology hokke engyō (法華円教, "Perfect Teaching of the Lotus Sutra") to imply it was the culmination of the previous sermons given by Gautama Buddha.[5] Further, because of the central importance of the Lotus Sutra, Tendai Buddhism includes such teachings as:

Tendai Buddhism uses a similar hierarchy as the Tiantai in to classify the various other sutras in the canon in relation to the Lotus Sutra, and it also follows Zhiyi's original conception of Five Periods Eight Teachings or gojihakkyō (五時八教). This is based on the doctrine of expedient means, but was also a common practice among East Asian schools trying to sort the vast corpus of writing inherited from Indian Buddhism.

A feature unique to Japanese Tendai Buddhism from its inception was the concept of shishūyūgō (四宗融合, "Integrating the Four Schools"). Under the umbrella of the Lotus Sutra, Tendai integrates four different aspects of practice:

In addition, sutras from each of these schools are revered, chanted and studied in Tendai.

In the early decades of the twentieth century, Buddhologist Shimaji Daito (1875–1927) introduced to the Japanese academic world a new interpretive category, which he called "original enlightenment thought" (Jpn. hongaku shiso). By this term he meant, in general, those strands of Buddhist thought, most prominent in East Asia and especially in Japan, that regard enlightenment or the ideal state as inherent from the outset and as accessible in the present, rather than as the fruit of a long process of cultivation. More specifically, Shimaji used "original enlightenment thought" to designate the intellectual mainstream of medieval Japanese Tendai Buddhism. In this medieval Tendai context, "original enlightenment thought" denotes an array of doctrines and concepts associated with the proposition that all beings are enlightened inherently. Not only human beings, but ants and crickets, mountains and rivers, grasses and trees are all innately Buddhas. The Buddhas who appear in sutras, radiating light and endowed with excellent marks, are merely provisional signs. The "real" Buddha is the ordinary worldling. Indeed, the whole phenomenal world is the primordially enlightened Tathāgata.[7]

Practices related to and veneration of Amitābha and his Sukhavati in the Tendai tradition began with Saichō's disciple, Ennin. After journeying to China for further study and training, he brought back a practice called the "five-tone nembutsu" or goe nenbutsu (五会念仏), which was a form of intonation practiced in China for reciting the Buddha's name. This contrasted with earlier practices in Japan starting in the Nara period, where meditation on images of the Pure Land, typically in the form of mandala, were practiced.[5][8]

However, both meditation on the Pure Land (kansõ nenbutsu 観想念仏) and recitation of the Buddha's name (shōmyō nenbutsu 称名念仏) became an integral part of Pure Land practices in the Tendai tradition. In addition to the five-tone nembutsu brought back from China, Ennin also integrated a special monastic training program called the jōgyō zanmai (常行三昧, "Constantly Walking samadhi") originally promulgated by Zhiyi. In this practice, monks spend 90 days in retreat, circumambulating a statue of Amitābha constantly reciting his name.[5]

In addition to increasing monastic practices related to the Pure Land, monks also taught Pure Land practices to the lay community in the form of reciting the Buddha's name. The most famous of these nenbutsu hijiri (念仏聖, "Itinerant Pure Land teachers") was a monk named Kūya (空也, 903-972).

Pure Land Buddhist thought was further developed by a Tendai monk named Genshin (源信, 942-1017) who was a disciple of Ryōgen, the 18th chief abbot or zasu (座主) of Mount Hiei. Genshin wrote a influential treatise called Ōjōyōshū (往生要集, "The Essentials of Rebirth in the Pure Land"), which vividly contrasted the Sukhavati Pure Land of Amitābha with the descriptions of the hell realms in Buddhism. Further, Genshin promoted the popular notion of the Latter Age of the Dharma, which posited that society had degenerated to a point when they could no longer rely on traditional Buddhist practices, and would instead need to rely solely on Amitābha's grace to escape saṃsāra. Genshin drew upon past Chinese Pure Land teachers such as Daochuo and Shandao.[8]

Finally, Pure Land practices in Tendai were further popularized by former Tendai monk Hōnen, who established the first independent Pure Land school, the Jōdo-shū, and whose disciples carried the teachings to remote provinces in one form or another. This includes another ex-Tendai monk named Shinran, who eventually established the related Jōdo Shinshū.

One of the adaptations by the Tendai school was the introduction of esoteric ritual into Tendai Buddhism, which was later named Taimitsu "Tendai Esotericism" (台密), distinguishing it from the Shingon Buddhist esoteric lineage known as Tōmitsu "Eastern Esotericism" (東密). Eventually, according to Taimitsu doctrine, the esoteric rituals came to be considered of equal importance with the exoteric teachings of the Lotus Sutra. Therefore, by chanting mantras, maintaining mudras, or performing certain meditations, one is able to see that the sense experiences are the teachings of Buddha, have faith that one is inherently an enlightened being, and one can attain enlightenment within this very body.

The origins of Taimitsu are found in Chinese Esoteric Buddhism similar to the lineage of Kūkai, and Saichō's disciples were encouraged to study under him.[9] As a result, Tendai esoteric ritual bears much in common with the explicitly Vajrayana tradition of Shingon, though the underlying doctrines may differ somewhat. Where Shingon sees esoteric teachings as the highest teachings in Buddhism, Tendai sees esoteric teachings as a means to an end in order to understand the profundity of the Lotus Sutra.

Another difference is the sutras and mandalas used. Where Shingon emphasizes the Mandala of the Two Realms, and by extension the Mahavairocana Tantra and the Vajrasekhara Sutra, for its esoteric practices, esoteric Tendai adds a third sutra called the Susiddhikāra Sūtra or Soshitsu Jikyō (蘇悉地経) and its related tantric practices.[5] Other differences mainly relate to lineages and outlook.

The existing lineage began with Saichō; however, his training had largely been limited to the Diamond Realm Mandala only.[2] After Saichō died, Ennin journeyed to China on the last diplomatic mission to China, and after extensive training, returned with both esoteric and Pure Land practices.[citation needed]

Tendai doctrine allowed Japanese Buddhists to reconcile Buddhist teachings with the native religion of Japan, Shinto, and with traditional Japanese aesthetics. In the case of Shinto, the difficulty is the reconciliation of the pantheon of Japanese gods, as well as with the myriad spirits associated with places, shrines or objects, with the Buddhist doctrine that one should not concern oneself with any religious practice save the pursuit of enlightenment. However, priests of the Tendai sect argued that Kami are simply that descend into the world to help mankind. Thus, they were seen as equivalent with Buddhas. This doctrine, however, regards Kami as more sacred. While Buddhas represent the possibility of attaining enlightentment through many lifetimes of work and devotion to Dharma, Kami are seen to be manifest representations of universal buddhahood. They exemplify the doctrine that all things are inherently enlightened and that it is possible for a person of sufficient religious faculties to attain enlightenment instantly within this very body.[citation needed]. Those Kami that Shinto regards as violent or antagonistic to mankind are considered as simply supernatural beings that are violent and evil.

The Buddha taught a Middle Way between the extremes of sensual indulgence and self-mortification. In the context of the Four Noble Truths this meant ceasing the craving (Sanskrit tṛṣṇā) of worldly desire and attachment, thus putting an end to suffering (dukkha). In early Buddhism, the emphasis, especially for monastics, was on avoiding activities that might arouse worldly desires. Buddhist art and poetry focused on overtly Buddhist themes. This tendency toward renunciation created a potential conflict with mainstream culture in China and Japan when Buddhism was introduced. Shedding worldly pleasures and attachments might seem to require that such flowers of culture as poetry, literature, and visual arts be given up.

However, later Mahayana views developed a different emphasis. By claiming that the phenomenal world is not distinct from Dharma, Tendai doctrine allows for the reconciliation of beauty and aesthetics with Buddhist teachings. Things are to be seen just as they are, as expressions of Dharma. Poetry, instead of being a potential distraction, now in fact can lead to enlightenment. Contemplation of poetry, provided that it is done in the context of Tendai doctrine, is simply contemplation of Dharma. This same thing can be said of other forms of art. Therefore, it is possible to construct an aesthetic that is not in conflict with Buddhism.

In the history of Tendai school, a number of notable monks have contributed to Tendai thought and administration of Mt. Hiei: