Shariputra, form does not differ from emptiness; 
emptiness does not differ from form.
Form itself is emptiness;
emptiness itself is form.
[cttbusa.org...]
 
Hua-yan Buddhism derived its name from the Hua-yan Sutra, translated as “The Flower Ornament Scripture” or as “The Flowery Splendor Scripture.” This extensive Buddhist text gives a very “flowery” description of the various stages of enlightenment; it also expounds the correct worldview, the correct ethical conduct, among other things. It probably was not composed by a single author, but was a compilation of various works circulating in India and its neighboring regions around the first and the second centuries AD. As far as we know no Indian Buddhist school was ever founded on the basis of this scripture.
The Hua-yan School, like its contemporary Tian-tai School, is indisputably a Chinese Buddhist school. Wing-tsit Chan says that it “represents the highest development of Chinese Buddhist thought.” The founder of the Hua-yan School was a Chinese monk named Du-shun (557-640). Though Hua-yan’s major sutra came from abroad, Du-shun established Hua-yan Buddhism by introducing new terminology to replace some key Indian notions.
 
 
He introduced the term li” (principle) to stand for the ultimate realm of reality [i.e. sunyata or “emptiness”]. This notion would prove to be one of the most important in Chinese philosophy. Du-shun used shi” (things or events [or phenomena]) to replace the term “form” in traditional Buddhist texts. This substitution manifests a more intense interest in the affairs of the phenomenal world. With this substitution, Hua-yan’s first patriarch took a subtle step away from the strong negation of the phenomenal world manifested in the Hua-yan Sutra. Du-shun also introduced the theory of the non-interference (or non-obstruction) of principle and things. Future patriarchs of the Hua-yan School would further develop his ingenious idea. [An Introduction to Chinese Philosophy, 248]
  • Does the shift in terminology from “emptiness” and “form” to “principle” and “phenomena” change the relationship in question?
Huayan Metaphysics
The Hua-yan Sutra denies that the phenomenal world really exists. The phenomenal world means the world we, as human beings, presently experience. In the Hua-yan Sutra, this world is likened to dream, illusion, phantom, echo, the magician’s conjuring, and the reflection in the mirror. Everything we perceive around us is also like a reflection or an illusion. As reflections, objects “have no location” and “no substantial nature.” As illusions, objects do not have a real beginning or end, nor do they have a definite origin or a final exit. In one synopsis, the Sutra says that all things “have no true reality.” [An Introduction to Chinese Philosophy, 250]
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For example, the second patriarch Zhi-yan says:
Since there is no separate objective realm outside of mind, we say “only mind.” If it operates harmoniously, it is called nirvana; therefore the [Sutra] says, “Mind makes the Buddhas.” If it operates perversely, it is birth-and-death [i.e. samsara]; therefore the [Sutra] says, “The triple world is illusory — it is only made by one mind.”
The third patriarch Fa-zang also says:
[W]hatever there is in the world is only the creation of one mind; outside of mind there is not a single thing that can be apprehended. ... It means that all discriminations come only from one’s own mind. There has never been any environment outside the mind which could be an object of mind.
[An Introduction to Chinese Philosophy, 252]
 
Hence, we could perhaps say that Hua-yan Buddhism is based on an anti-realistic attitude toward this mundane world. This feature of subjective idealism and anti-realism seems to have been overlooked by many Hua-yan commentators. ...
 
 
[On the other hand,] Cook argues that for the Hua-yan School, “the emptiness doctrine should not be understood as a naive rejection of the material world as pure illusion; it indeed recognizes the existence of the natural world but denies that it has any duration or independent being. In fact, being is rejected in favor of a constant, never-fully-completed becoming.” Under this interpretation, the world we live in is an organic whole constantly evolving and transforming. What is denied is simply the self-subsistence of individual entities, not the whole system. Did Fa-zang revolutionize Hua-yan Buddhism so much as to turn its spirit of idealism into realism? Let us turn to Fa-zang’s view in particular. [An Introduction to Chinese Philosophy, 253]
 
Fa-zang builds up from the interpenetration of multiple worlds to expound his view of the interconnectedness of multiple things within each world. He uses the gold lion example to illustrate that the whole phenomenal world, the Realm of Things, is like one single object, each part of which is inseparable from the other parts. Without any of the multiple parts of the lion, the whole lion cannot exist; without the whole lion, no part of the lion could possibly exist. By the same token, with any single thing lacking in the phenomenal world, the whole world would not exist; without the whole world, no single thing can exist. There is thus mutual entailment between the whole and its parts. This kind of view is now considered a form of holism, the thesis that any single item within a particular system is part of the whole system and cannot be considered independently of the whole. [An Introduction to Chinese Philosophy, 258]
 
Even though Hua-yan Buddhism views all objects and events in the whole universe as mutually causally dependent and as ontologically interconnected, it does not posit a real causal network among them. To assume that there are any real causal connections among things is to assume that causality itself is real and that causal agents are real. Both claims are denied by Hua-yan philosophers. The only real causal agent should be the Mind only, which produces multiple minds, which in turn through their delusions create multiple things. Even though from our perception there are primary and subsidiary causes that can be discerned in each effect, ultimately both causes and effects are only “epiphenomena” superimposed by the real cause — the Mind. [An Introduction to Chinese Philosophy, 261]
 

The First Approach
First is the ordinary experience of existence that reveals the “realm of phenomena” (Chinese: shih), or the myriad dharmas. According to Hua-yen, this is the vision of the cosmos with which the early Buddhist tradition, such as Theravada, works in order to gain Nirvana by the purification of the negative phenomena in one’s consciousness. [Buddhism: Introducing the Buddhist Experience, 214]
 
The Second Approach
Second is the experience of existence that reveals the emptiness of all phenomena, the true suchness of all things. This is the “realm of principle” (Chinese: li), with which Mahayana works in order to attain Buddhahood. Through this second vision, one realizes that the real and inherent “principle,” or nature of things, is always pure. While phenomena may be either pure or impure, in essence they are empty of the independent nature one conceives them to have. Realizing this emptiness, the dependent arising of existence, reveals the inherent purity as the Buddha-nature of all phenomena. This inherent purity as the principle of existence is likened to a clear mirror. While the mirror may reflect pure and impure images, its essential clarity is never lost. [BIBE, 214]
 
The Third Approach
Now we come to the third experience of the cosmos, namely, seeing “the realm of the non-obstruction between principle (li) and phenomena (shih).” This non-obstruction refers to the fundamental Mahayana identity of emptiness with phenomena, or Nirvana with samsara. For Hua-yen, these two aspects of reality “interpenetrate” such that the essential purity of suchness is not lost, and the diversity of dependently arisen phenomena is maintained.
  
Treatise on the Golden Lion
Once Fa-tsang presented this notion of mutual penetration in a lecture to Empress Wu. In her palace, he used a golden statue of a lion to illustrate his ideas. Later, he used this lecture to compose his famous Treatise on the Golden Lion. ... In the first gate, it is said that the gold (emptiness) and the lion (the totality of phenomena or forms) come into being simultaneously. In the second gate, it is said that the oneness of this dependent arising in which all things condition each other does not obstruct the unique identities of each thing in the cosmos. [BIBE, 216]
 
 
When we view the lion as a whole, we see its totality; when we view each part of the lion, we see their individuality; when we see that all parts are parts of the same lion, we see their similarity; when we see that each part is nonetheless different from one another, we see their differences; when we see the various parts coming together to form the lion, we see the integration; when we see the lion eventually breaks down to individual parts, we see the disintegration. In all objects as well as in the whole phenomenal world, these six aspects (totality, individuality, similarity, difference, integration, and disintegration) are present. Manifesting one aspect does not prevent the thing from manifesting all other aspects. In this respect, the six aspects are harmoniously contemplated. The point of this theory is again to emphasize that things do not have inherent self-nature. the way things are — their characteristics, their natures — are nothing but the way they are contemplated by the mind. Different perspectives generate different characteristics; the real perspective is the one that encompasses all perspectives and sees them as harmoniously compatible with one another. [An Introduction to Chinese Philosophy, 260-1]
 
 
Form and Emptiness
2. This means that the form of the lion [i.e. the realm of phenomena] is unreal ; what is real is the gold [i.e. emptiness — the realm of principle]. Because the lion is not existent [since it is “empty”], and the body of the gold is not non-existent [since it has “quasi existence” within the infinitely malleable matrix of reality], they are called form/Emptiness. Furthermore, Emptiness does not have any mark of its own; it is through forms that [Emptiness] is revealed [i.e. principle is “unconditioned” since it is the thusness of reality itself, but it finds expression in “conditioned” things]. This fact that Emptiness does not impede the illusory existence of forms is called form/Emptiness. [www.thezensite.com...; cf. BIBE, 216]
 
 
The Fourth Approach
Finally we arrive at the fourth experience of the cosmos in which one sees “the realm of the non-obstruction between phenomena (shih and shih).” Here, we are not looking at the relationship between emptiness and phenomena, but at the relationship between the phenomena themselves. For Hua-yen, the vision of this non-obstruction reveals that the dependent arising of all phenomena exists as a totality of dynamic interrelatedness. It also reveals that the phenomena making up this totality are related to one another by what Hua-yen calls “mutual identification” and “mutual penetration.” [BIBE, 215]
 
The jeweled net of Sakra is also called Indra’s Net, and is made up of jewels. The jewels are shiny and reflect each other successively, their images permeating each other over and over. In a single jewel they all appear at the same time, and this can be seen in each and every jewel. There is really no coming or going. Now if we turn to the southwest direction and pick up one of the jewels to examine it, we will see that this one jewel can immediately reflect the images of all of the other jewels. Each of the other jewels will do the same. Each jewel will simultaneously reflect the images of all the jewels in this manner, as will all of the other jewels. The images are repeated and multiplied in each other in a manner that is unbounded. Within the boundaries of a single jewel are contained the unbounded repetition and profusion of the images of all the jewels. The reflections are exceedingly clear and are completely unhindered.
 

 
If you sit in one jewel, you will at that instant be sitting repeatedly in all of the other jewels in all directions. Why is this? It is because one jewel contains all the other jewels. Since all the jewels are contained in this one jewel, you are sitting at that moment in all the jewels. The converse that all are in one follows the same line of reasoning. Through one jewel you enter all jewels without having to leave that one jewel, and in all jewels you enter one jewel without having to rise from your seat in the one jewel. [Sources of Chinese Tradition, 473]
  • In her discussion of the Huayan Sutra (quoted above), JeeLoo Liu notes that the text manifests a “strong negation of the phenomenal world,” since all phenemona are ultimately a manifestation of the Mind only (as understood by the Consciousness-Only school in An Introduction to Chinese Philosophy, 220-47). Do you think that the parable of Indra’s Net represents a negation or an affirmation of the phenomenal world?
  • How might Du Shun’s new terminology of li (“principle,” referring to the ultimate realm of reality, namely emptiness with its implication of interdependent origination) and shi (“thing” or “event,” referring to the realm of forms or “phenomena”) be used to interpret the parable?
  • Where’s the “center” of the net?
 
Mutual Identification
The mutual identification of all things does not imply a kind of static identification by which one might say, for example, that fire is the same as ice. Rather, in the Hua-yen vision, all phenomena in the cosmos are dependently arising together simultaneously. Each phenomenon provides a condition for the arising of the whole cosmos, and the particular totality of the cosmos is dependent on the conditions provided by all of its parts. If one part, one thing, was different or not present, the totality would itself be different. In dependent arising, each phenomenon plays an identical role in the mutual forming of the universe. ... In realizing this mutual identification, a person discovers that he or she owes his or her existence to countless beings throughout the universe. This discovery gives one a deeper sense of gratitude and respect for other beings. One also feels a deeper sense of responsibility for how one uses his or her existence, given its effect on the universe. This discovery will also give one a greater aspiration to benefit all living beings (bodhicitta). [BIBE, 215-6]
 
Treatise on the Golden Lion
Mastering the Ten Mysteries/Gates
[7] In each eye, ear, limb, joint and hair of the lion is [reflected] a golden lion. All these golden lions in all the hairs simultaneously enter into a single hair. Thus in each hair, there are an infinite number of lions. In addition, all single hairs, together with their infinite number of lions, enter into a single hair. In a similar way, there is an endless progression [of realms interpenetrating realms] just like the jewels of Indra’s net. [BIBE, 217]
 
Mutual Penetration
The idea of mutual penetration takes this notion of mutual identification a step further. In the Hua-yen teaching about the mutual penetration of phenomena, we find the high point of Hua-yen experience that has been so important to defining East Asian Buddhism. ... Fa-tsang says that even though the forms of life are distinct, they also interpenetrate so that they “contain” each other. By this he means that in dependent arising, the very presence of each phenomenon influences or conditions the other phenomena of the cosmos. The conditioning influence of one phenomenon “enters” into all other phenomena, Fa-tsang says, like reflections of objects enter a mirror. Note here that Fa-tsang does not say that the phenomena physically enter each other.
 
 
Once, in order to demonstrate this interpenetration to Empress Wu, Fa-tsang placed a statue of the Buddha with a lamp in the middle of a room with mirrors all around it. He then showed the empress how the image of the Buddha-statue (representing emptiness), while physically remaining at the center of the room, was reflected in each mirror (representing phenomena). He also showed her that each mirror, while physically remaining where it is, was reflected in all other mirrors, and that their mutual reflection (representing mutual penetration) was repeated infinitely. In a similar way, each phenomenon in the cosmos contains the presence of all other phenomena in the cosmos, while at the same time retaining its uniqueness. [BIBE, 216-7]
 
Treatise on the Golden Lion
Mastering the Ten Mysteries/Gates
[3] If the eye of the lion takes in the whole lion, then the whole lion is purely the eye. ... [4] Since the various organs, and even each hair of the lion, takes in completely the whole lion in so far as they are all gold, then each [element of the lion] penetrates the whole [of the lion]. The eye of the lion is its ear, its ear is its nose, its nose is its tongue, and its tongue is its body. Yet, they all exist freely and easily, not hindering or obstructing each other. [BIBE, 217]
 
Huayan in Practice
In Hua-yen practice, tranquility meditation is used to enable a person to find emptiness as the quiescent nature of all things. This leads to detachment and inner calm in the midst of the world. Then through insight meditation one sees this emptiness functioning as the forms of the world. This functioning is experienced as an interpenetrating, fascinating, and wonderful matrix of dependent arising. This insight, in turn, leads to a rejection of world renunciation and a compassion for all living beings who fail to see this hidden harmony and are caught in afflictive mental formations. Thereby, one dwells spiritually neither in samsara nor Nirvana but courses freely as a bodhisattva in the matrix of the cosmos seeking the benefit of others. Hua-yen’s vision of this matrix of mutual identification and penetration, where all things are interwoven in perfect balance and harmony, was very appealing to the Chinese world, which had always appreciated both harmony and nature. [BIBE, 218]
  • So in the end, is Huayan a world-affirmingor a world-denying tradition?