The Huayan or Flower Garland school of Buddhism (traditional Chinese: 華嚴; ; pinyin: Huáyán, from Sanskrit: Avataṃsaka) is a tradition of Mahayana Buddhist philosophy that first flourished in China during the Tang dynasty. The Huayan worldview is based primarily on the Avatamsaka Sutra (Chinese: 華嚴經; pinyin: Huáyán jīng). The name Flower Garland is meant to suggest the crowning glory of a Buddha's profound understanding of ultimate reality.
The earliest texts associated with the Avatamsaka sutra are the Dousha jing (Taisho 280), produced by Lokaksema in the latter part of the second century CE and the Pusa benye jing (T. 281), translated by Zhi Qian in the early to mid third century. There is evidence that these small Buddhavatamsaka sutras circulated on their own as individual scriptures.
The translation of the large Avatamsaka sutra is often dated to the Southern Dynasties (420-589) when a translation team led by Gandharan master, Buddhabhadra worked on the sutra. There is also evidence of this sutra tradition in the Northern Dynasties (386-581) where a certain Xuangao (402-444) taught the Huayan samadhi.
The five monks later honored as Huayan patriarchs were erudite scholar-practitioners who connected Buddhism with Chinese traditional culture closely, creating a Buddhist historical trend in developing multiple facets while the tradition’s essence remained the same. Based on their writings, exegeses, and oral teachings, these men each played a significant and distinct role in the development of the school, although there are certain aspects of this patriarchal scheme which are clearly contrived. For example, Chengguan was born 26 years after Fazang's death. According to Robert Gimello's dissertation on Chih-Yen (1976), "most if not all of the major themes of Huayen thought" can be found in the works of the second patriarch Chih-yen, particularly the classification of scriptures and theories on the Dharmadhatu. Thus he names the patriarch Chih-yen (602-668) as the crucial figure in the foundation of Huayan. The tradition reached the height of its influence under Fazang, who was the Buddhist teacher of the Empress Wu Zetian (684–705).
Another important figure in the development and popularization of Huayan thought was the lay scholar Li Tongxuan (Chinese: 李通玄, 635?-730), the author of the Huáyán lùn (Chinese: 華嚴論), a popular and lengthy commentary on the Avatamsaka sutra. Fazang's disciple Huiyuan (673-743) also wrote a commentary on the Avatamsaka.
After the time of Zongmi and Li Tongxuan the Chinese school of Huayan generally stagnated in terms of new development, and then eventually began to decline. The school, which had been dependent upon the support it received from the government, suffered severely during the Buddhist purge of 841-845, initiated by Emperor Wuzong of Tang, never to recover its former strength. Nonetheless, its profound metaphysics, such as that of the Four Dharmadhātu (Chinese: 四法界) of interpenetration, had a deep impact on surviving East Asian schools.
The Huayan school's worldview was inspired on the content of what it considered to be the supreme Buddhist revelation, the Avataṃsaka Sūtra (Flower Garland Sutra, Ch. Huāyán Jīng). The Avataṃsaka Sūtra is a compilation of sutras of various length, which originally circulated as their own sutras before being combined. The earliest of these texts, the Ten Stages Sutra, maybe dates from the first century CE. The Daśabhūmika Sūtra describes the ten stages on the Bodhisattva-path. The various sutras were probably joined together shortly before its translation into Chinese, at the beginning of the 5th century CE.
According to Williams, the Avataṃsaka Sūtra is not a systematic philosophical work, but mentions various Mahayana teachings, including Madhyamaka śūnyatā teachings, Yogacara ideas, as well as mentioning a pure untainted awareness or consciousness (amalacitta). It is filled with mystical and visionary imagery, focusing on the Buddha Vairocana, who is said to pervade every atom of the entire universe with his magical creations and emanations as a way to help all beings:
Are countless worlds and Buddhas...
From the tip of each hair of Buddha's body
Are revealed the indescribable Pure Lands...
The indescribable infinite Lands
An important doctrine that the Huayan school drew from this sutra is the idea that all levels of reality are interrelated and interpenetrated, the idea that "inside everything is everything else". The sutra states:
They . . . perceive that the fields full of assemblies, the beings and aeons which are as many as all the dust particles, are all present in every particle of dust. They perceive that the many fields and assemblies and the beings and the aeons are all reflected in each particle of dust.
In the Huayan school, this is depicted in the image of Indra's net. This "unity in totality allows every individual entity of the phenomenal world its uniqueness without attributing an inherent nature to anything". According to Williams,
As a description of the way things are in our unenlightened world this seems incredible. But the dharmadhatu is the world as seen by the Buddha wherein there is no question of the world (an objectively real world ‘out there’) as distinct from meditative vision. Thus the sutra is less concerned with describing the world this way as with recounting the Bodhisattva’s attainments by which he can see the world in such a light, and the Bodhisattva’s miraculous powers by which, through his magical interventions in this world with no fixed hard boundaries, he can cause things to interpenetrate.
Other Mahayana texts such as the Awakening of Faith in the Mahayana (Dasheng Qixin Lun 大乘起信論), which was a condensation of Chinese thought on awakening and ultimate reality, influenced Huayan masters like Fazang and Zongmi, who both wrote commentaries on the text. The Lotus sutra was also seen as an important text in this school, though not as important as the Avatamsaka. The Sutra of Perfect Enlightenment was particularly important for Zongmi.
The Huayen patriarchs wrote numerous commentaries and original treatises on the Mahayana sutras and Huayen philosophy. Fazang for example, wrote commentaries on the Avatamsaka, the Lankavatara Sutra and the Awakening of Faith. One of the key Huayen treatises is On the Meditation of the Dharmadhātu attributed to the first patriarch Dushun. Another is Fazang’s Treatise on the Golden Lion which is said to have been written to explain Huayen's view of interpenetration to Empress Wu.
"not primarily concerned with a careful exegesis of the original meaning of the scripture. Rather, what it discovered in the text was the justification for a number of ideas and metaphors in terms of which it elaborated its own body of doctrine. Many of the key Huayan doctrines that were inspired by the scripture (such as nature origination, the conditioned origination of the dharmadhatu, the samadhi of oceanic reflection, or the six aspects of all dharmas) played only a peripheral role in or had a tenuous connection with the actual Huayan sutra itself. The great commentaries written on the text by Fa-tsang and Ch'eng-kuan were not so much concerned with rendering a faithful and judicious interpretation of the words of the text as they were with using the text as a basis from which to advance a doctrinal agenda that was determined by the context of Sui-Tang Buddhism."
Huayan thought is mainly focused on explaining the nature of the Dharmadhatu, the world as it is ultimately, from the point of view of a fully awakened being. It is often said to be the philosophical articulation of Chan meditation. It is influenced by the Avatamsaka and Buddha nature literature as well as by the Chinese Yogacara and Madhyamaka schools. Patriarchs of the school such as Zongmi were also influenced by Chinese philosophy, particularly the classics of Taoism.
A key doctrine of Huayan is the mutual containment and interpenetration of all phenomena (dharmas) or "perfect interfusion" (yuanrong, 圓融). This is associated with what the Huayan sees as its unique contribution, the "dharmadhatu pratityasamutpada". This is described by Wei Daoru as the idea that "countless dharmas (all phenomena in the world) are representations of the wisdom of Buddha without exception" and that "they exist in a state of mutual dependence, interfusion and balance without any contradiction or conflict. This thought essentially argues that there is no relationship of cause and result among phenomena and that things are not formed sequentially. Instead, they constitute the world by the mutual interfusion of complete equality."
According to this theory, any phenomenon exists only as part of the total nexus of reality, its existence depends on the total network of all other things, which are all equally connected to each other and contained in each other.
"called for a candle and placed it surrounded by mirrors on every side. When lit, the candle was reflected in each mirror, and each of the reflections in every other mirror so that in any one mirror were the images of all the others."
Another important distinction used by Huayan patriarchs is that of li and shi, noumenon and phenomenon which was explained using the metaphor of gold and lions, or water and waves. According to Paul Williams:
First, noumenon and phenomena mutually interpenetrate and are (in a sense) identical. There is no opposition between the two. The one does not cancel out the other. Second, Fazang explains elsewhere that since all things arise interdependently (following Madhyamika), and since the links of interdependence expand throughout the entire universe and at all time (past, present, and future depend upon each other, which is to say the total dharmadhatu arises simultaneously), so in the totality of interdependence, the dharmadhatu, all phenomena are mutually interpenetrating and identical.
The theory of the Fourfold Dharmadhatu (sifajie, 四法界) is explained in the "Meditative Perspectives on the Huayan Dharmadhatu" (Huayan Fajie Guanmen, 華嚴法界觀門) and its commentaries. This theory is the central meditative framework for the Huayan tradition. Another key text is the "Cessation and Contemplation in the Five Teachings of Huayan" (Huayan wujiao zhiguan 華嚴五教止觀). The Dharmadhatu is the goal of the bodhisattva's practice, the ultimate nature of reality which must be known or entered into (ru, 入). According to Fox, the Fourfold Dharmadhatu is "four cognitive approaches to the world, four ways of apprehending reality".The four ways of seeing reality are: 
The three levels of Huayan meditation on the Dharmadhatu correspond to the last three views of the Dharmadhatu are:
According to Fox, "these dharmadhatus are not separate worlds – they are actually increasingly more holographic perspectives on a single phenomenological manifold...they more properly represent four types or orders of perspectives on experience." Furthermore, for Huayan, this practice is the solution to the problem of samsara which lies in the "fixation or attachment to a particular perspective. What we think are the essences of objects are really therefore nothing but mere names, mere functional designations, and none of these contextual definitions need necessarily interfere with any of the others."
According to Paul Williams, the reading and recitation of the Avatamsaka sutra was also a central practice for the tradition, for monks and laity.
Layman Li Tongxuan developed a unique meditative practice based on the 9th chapter of the Avatamsaka sutra. The practice, named 'the contemplation of Buddhalight' (foguang guan), focused on tracing the universal light which is radiated by the Buddha in one's mind and expanding it further outwards.
Huayan favored the teaching of sudden enlightenment. This is because the Buddha nature is already present in all sentient beings and also because their theory of interpenetration entails that Buddhahood is already present at the first stage of a Bodhisattva's path. According to Li Tongxuan:
[T]he first access of faith in the mind of the practitioner is in itself the culmination of the entire path, the very realization of final Buddhahood.... ‘Faith’ or confidence in the possibility of enlightenment is nothing but enlightenment itself, in an anticipatory and causative modality.
Buddhahood was seen as beyond language and stages of practice. Because practices cannot create something that is already not imminent, they were seen as simply revealing what was already there. The patriarch Zongmi formulated his own theory of awakening which was "immediate awakening followed by gradual cultivation" and the view that "immediate and gradual are not only not contradictory, but are actually complementary".
Huayan makes extensive use of paradox in argument and literary imagery. All three types of paradox originate in the tension between conventional and absolute truth. Huayan uses three types of paradox:
1. Emphasizing the concept of śūnyatā, first is asserted that a phenomenon X is empty, which implies that X is not X. An example from Fazang is the assertion:
[W]hen one understands that origination is without self-nature, then there is no origination.
2. Reversing the first paradox by asserting that any empty phenomenon is an expression of the absolute non-duality between emptiness and form, or the identity between conditioned, relative reality and the ultimate truth of tathatā. This paradox is derived from two doctrinal sources:
When the great wisdom of perfect clarity gazes upon a minute hair, the universal sea of nature, the true source, is clearly manifest.
3. The third variation of paradox is grounded in the Huayan doctrine of the "nonobstruction of all phenomena" (shih shih wu-ai(k)). Each phenomenon is perceived as interpenetrating with and containing all others. This paradoxical violation of the conventional order of time and space is exemplified by Fa-tsang's famous "Essay on the Golden Lion":
In each and every hair [of the lion] there is the golden lion. All of the lions contained in each and every hair simultaneously and suddenly penetrate into one hair. [Therefore], within each and every hair there are unlimited lions.
Buddhism was introduced into China in bits and pieces. When the knowledge of Buddhism grew larger, various schools attempted to get a grip on the Buddhist tradition by developing classifications of teachings, such as the Five Periods and Eight Teachings of the Tiantai-school.
Huayan and Chán had doctrinal arguments regarding which would be the correct concept of sudden awakening. The teachings of the Chán-school were regarded as inferior by the Huayan teachers. The Chán-school polemitized against this classification, by devising its own rhetorics in defense.
The doctrines of the Huayan school ended up having profound impact on the philosophical attitudes of East Asian Buddhism. According to Wei Daoru their theory of perfect interfusion was "gradually accepted by all Buddhist traditions and it eventually permeated all aspects of Chinese Buddhism."
Chinese Chán was profoundly influenced by it, though Chán also defined itself by distinguishing itself from Huayan. Tsung-mi, the Fifth Patriarch of the Huayan school, also occupies a prominent position in the history of Chán. During the Song, the Huayan metaphysics were completely assimilated by the Chán-school.