Mandalas as expressions of the Buddhist cosmos
In purely formal terms, mandalas[1] are graphic illustrations of the Buddhist cosmos, in the shape of a diagram that represents Buddhist deities in a geometric pattern of varying complexity. In most cases, they are paintings on canvas or paper but mandalas can also be tri-dimensional and take the shape of a group of statues or ritual instruments. Buddhist deities[2] may be represented under their human guise (in two or three dimensions) or symbolised by an attribute attached to them (jewel, bowl, sword, rope, etc.) or by a Sanskrit syllable that identifies them. We thus arrive at four different types of mandalas that may be interwoven: the Great Mandala[3], the Samaya Mandala[4], the Dharma Mandala[5] and the Karma mandala[6]. As to composition, a mandala may represent or symbolise all Buddhist deities, only a family (or a class) of deities, or one, singled out, deity.
It is no easy task to establish the origin of Buddhist mandalas, however the key driving factor in their development sprang from esoteric Buddhism[9], a late current that developed in India between the 7th and 8th centuries and spread almost simultaneously to Tibet and China then to Japan at the very beginning of the 9th century. Esoteric Buddhism is one branch of Mahāyāna Buddhism, that is Buddhism of the Great Vehicle, the most widespread form of Buddhism in Eastern Asia. According to the many schools spawned by the Great Vehicle some time around the turn of the Christian era, Buddhist Enlightenment[10] can be achieved by every sentient being, not just monks. This sets it apart from older Buddhist traditions, notably the Theravāda[11][11]. Another difference between the exponents of each school rests with the fact that the Theravāda tradition holds that only one Buddha lives at any given time, whereas according to Mahayana the cosmos abounds with buddhas and bodhisattvas[12] intent on assisting sentient or living beings in their spiritual quest.
Esoteric Buddhism is founded in elaborate ritual systems. It further develops the concept of a multitude of buddhas in the “Three Worlds” (past, present and future) adding to it a different notion, that of emanation: every single element of the cosmos is nothing but an emanation or a manifestation of the universal Buddha named Mahāvairocana, the "Great Enlightener". Thus esoteric Buddhism takes the principle of the accessibility of Buddhist realisation to its utmost conclusion, setting forth a system of total osmosis between microcosm and macrocosm. Accordingly any living being not only partakes of Buddha Nature but has the ability to realise it fully in this life: it is possible for absolutely anybody to break the chain of transmigrations and to “become a buddha in this very body” (sokushin jōbutsu). Esoteric mandalas offer a visual expression of this notion of emanation: the central divinity which represents the universal Buddha, that is Buddhist realisation, radiates outwards and creates reciprocal relations with its multiple manifestations, which get reflected as in a game of mirrors: all is one, and each one is all.
The Japanese monk[13] Kūkai is the founder of the Shingon School[14], and one of the most influential religious figures in the whole history of Japan. Initiated into esoteric Buddhism during his stay in China, he later developed a highly complex philosophical and conceptual framework for this particular tradition. From China, he also brought back with him a large number of works and objects that he described in a catalogue. Under the heading of iconic Buddhist objects, he included the portraits of patriarchs as well as several mandalas, which represent for him not only the condensed version of the esoteric doctrine but indeed of the entire Buddhist cosmos [doc 28]. According to him, the two mandalas accounting best for this cosmos are the Mandala of the Womb World in conjunction with that of the Diamond World. The first graphic version of these two mandalas is attributed to the entourage of Huiguo[15], the Chinese monk who was Kūkai's master. Though not an exact transcription, this “dual mandala” or "Mandala of the Two Worlds" (Ryōkai Mandara) is related to the two fundamental texts from which the doctrines of esoteric Buddhism evolved, namely the Sūtra of the Great Enlightener and the Diamond Peak Sūtra[16]. Initially originating from two different esoteric lineages, the two sūtras[17] are understood in esoteric Buddhism as being both inseparable and interdependent.