The termhonji suijaku orhonchi suijaku (本地垂迹) in Japanese religious terminology refers to a theory widely accepted until theMeiji period according to which IndianBuddhist deities choose to appear inJapan as nativekami to more easily convert and save theJapanese.[1][2] The theory states that somekami (but not all) are local manifestations (thesuijaku (垂迹), literally, a "trace") of Buddhist deities (thehonji (本地), literally, "original ground").[1][3] Thus, for example, the deityAmaterasu was considered a trace ofDainichi Nyorai (Great Sun Buddha).[4]
According to the theory, the two elements form an indivisible whole calledgongen, and in theory should have equal standing, but this was not always the case.[5] In the earlyNara period, for example, the original ground (honji) was considered more important and only later did the two come to be regarded as equals.[5] During the lateKamakura period some theories proposed that thekami were the original deities and the buddhas their manifestations (see theInverted honji suijaku section below).[5]
Honji suijaku theory was never systematized but it was nonetheless very pervasive and very influential onJapanese religions.[1] It is considered the keystone of theshinbutsu-shūgō (syncretism of Buddhist deities and Japanesekami) edifice.[6]Honji suijaku has often been seen as similar tointerpretatio Romana, a mode of comparison promoted in antiquity by scholars such asTacitus who argued thatbarbarian gods were just the foreign manifestations of Roman or Greek deities.[7]
The termhonji suijaku itself is an example of the Japanese practice ofYojijukugo, a four-character combination of phrases which can be read literally or idiomatically.

Early Buddhist monks did not doubt the existence ofkami but saw them as inferior to theirbuddhas.[1] Hindu deities had had the same reception: They were thought of as non-illuminated and prisoners ofsaṃsāra.[1] Buddhist claims of superiority, however, encountered resistance; monks tried to overcome it by deliberately integratingkami in their system.[1] Japanese Buddhists themselves wanted to somehow give thekami equal status.[1] Several strategies to do this were developed and employed, and one of them was thehonji suijaku theory.[1]
The expression was originally developed in China[8] and used byTendai Buddhists to distinguish an absolute truth from its historical manifestation (for example, the eternalBuddha from the historical Buddha, or the absoluteDharma from its historical forms, the first being thehonji, the second thesuijaku).[1][3] The term makes its first appearance with this meaning in theEizan Daishiden, a text believed to have been written in 825.[3] Thehonji suijaku theory proper later applied it to buddhas andkami, with its first use within this context dated to 901, when the author of theSandai Jitsuroku says that "mahasattvas (buddhas andbodhisattvas) manifest themselves at times as kings and at times askami."[3] The dichotomy was applied to deities only in Japan and not, for example, in China.[1]
A different but equivalent explanation, the idea that Buddhist deities choose not to show themselves as they are, but manifest themselves askami, was expressed in a poetic form with the expressionwakō dōjin (和光同塵), which meant that to assist sentient beings, deities "dimmed their radiance and became identical to the dust of the profane world."[1] Their brightness would otherwise be such to destroy mere mortals.[1]
In the 10th and 11th centuries there are numerous examples of Buddhist deities andkami pairings: The deities are usuallyKannon,Yakushi,Amida orShaka Nyorai.[1] The association between them was usually made after a dream or revelation made to a famous monk, later recorded in a temple's or shrine's records.[1] By then,kami in Japan were universally understood to be the form taken by buddhas to save human beings, that is, local manifestations of universal buddhas.[9] Around the beginning of theKamakura period the pairings had become solidly codified in large temples or shrines.[1] The frequency of the practice is attested by thekakebotoke (懸仏), or "hanging buddhas," found in many large shrines—metal mirrors that carry on the front the effigy of the shrine'skami and on the rear the relative Buddhist deity.[1] The name shows that they are usually hung from a shrine's outer wall.[1]
As the theory gradually spread around the country, the concept ofgongen ("provisional manifestation", defined as a Buddha that chooses to appear to the Japanese as akami[3]) evolved.[1] One of the first examples ofgongen is Hie's famousSannō Gongen (山王権現).[1] Under the influence ofTendai Buddhism andShugendō, thegongen concept was adapted, for example, to religious beliefs tied toMount Iwaki, a volcano, so that femalekami Kuniyasutamahime became associated with JūichimenKannon Bosatsu (eleven-faced Kannon),kamiŌkuninushi withYakushi Nyorai, andKunitokotachi no Mikoto withAmida Nyorai.[10]

Thehonji suijaku paradigm remained a defining feature of Japanese religious life up to the end of theEdo period. Its use was not confined to deities but was often extended even to such historical figures asKūkai andShōtoku Taishi.[1] It was claimed that these particular human beings were manifestations ofkami, which in turn were manifestations of buddhas.[1] Sometimes the deity involved was not Buddhist.[1] This could happen because the theory was never formalized and always consisted of separate events usually based on a temple or shrine's particular beliefs.[1]
Nothing was fixed: A deity could be identified both as ahonji and asuijaku in different parts of the same shrine, and different identifications could be believed to be true at the same time and place.[1] The religious situation during the Middle Ages was, therefore, confused and confusing. Historians have tried to concentrate on the reformers of that age with a clear philosophy and little interest inkami questions because they are easier to understand.[1] The theory was ultimately beneficial to thekami, which went from being considered unilluminated outsiders to actual forms assumed by important deities.[1] The ultimate expression of this shift isRyōbu Shintō, in which Buddhist deities andkami are indivisible and equivalent like the two sides of a coin.[1]
The use of thehonji suijaku paradigm was not limited to religion—it had important consequences for society in general, culture, art and even economy.[11] Buddhism, for example, proscribed fishing, hunting, and agriculture because they involved the killing of living beings (insects, moles and the like in the case of farming), but thehonji suijaku concept permitted people to void the prohibition.[12] If one fished for oneself, the reasoning went, you were guilty and should go to hell. However, if the catch was offered to akami that was a known emanation of a buddha, the gesture had an obvious karmic value and was permissible.[12] The idea allowed the forbidding of individual, and therefore uncontrolled, economic activity.[12] Applied as it was to all major economic activities, this interpretation ofhonji suijaku allowed a thorough control of popular dissent.[12]
How important the concept was can be understood from how the idea that some local phenomenon may be somehow linked to an absolute and sacred object found extensive application in the medieval and early modern periods.[11] It was often said that temple lands in Japan were local emanations of Buddhist paradises or that an artisan's work was one with the sacred actions of an Indian Buddha.[11]

Thehonji suijaku paradigm found wide application in religious art with theHonji Suijaku Mandara (本地垂迹曼荼羅) orSongyō Mandara (尊形曼荼羅).[13] TheHonjaku Mandara (本迹曼荼羅) (see image above) shows Buddhist deities with theirkami counterparts, while theHonjibutsu Mandara (本地仏曼荼羅) show only Buddhist deities, and theSuijaku Mandara (垂迹曼荼羅) show onlykami.[13]
TheSōgyō Hachiman (僧形八幡), or "Hachiman in priestly attire", is one of the most popular syncretic deities.[14] Thekami is shown dressed as a Buddhist priest and is considered the protector of people in general and warriors in particular.[14] From the 8th century on, Hachiman was calledHachiman Daibosatsu, or GreatBodhisattva Hachiman.[14] That he is dressed like a Buddhist priest is probably meant to indicate the sincerity of his conversion to Buddhism.[14] By the 13th century, otherkami would also be portrayed in Buddhist robes.[14]
The Shintōshū is a book in ten volumes believed to date from theNanboku-chō period (1336–1392).[15] It illustrates with tales about shrines thehonji suijaku theory. The common point of the tales is that, before reincarnating as tutelarykami of an area, a soul has first to be born and suffer there as a human being.[16] The suffering is mostly caused by relationships with relatives, especially wives or husbands.
The book had great influence over literature and the arts.[15]
The dominant interpretation of the buddha-kami relationship came to be questioned by what modern scholars call theinverted honji suijaku (反本地垂迹,han honji suijaku) orshinpon butsujaku (神本仏迹) paradigm, a theology that reversed the original theory and gave the most importance to thekami.[17] Supporters of the theory believed that, while those who have achieved buddhahood have acquiredenlightenment, akami shines of his own light.[17] The doctrine was first developed byTendai monks, and its first full formulation is attributed toJihen, a monk tied to the greatIse shrine who was most active around 1340.[17] In the first fascicle of theKuji hongi gengi he argued that, in the beginning, Japan had onlykami and that only later did buddhas take over.[18] He believed that for this reason there had been a decadence in the country's morals and that a world wherekami dominated would soon reappear.[18] In the fifth fascicle of the same work, he compared Japan to a seed, China to a branch and India to a flower or fruit.[18] Just like flowers that fall and return to the roots, India had come back to its roots, thekami were thehonji and the buddhas their manifestations.[18]
Yoshida Kanetomo, a JapaneseShinto priest of theSengoku period, was influenced by these ideas and brought them further, making a clean break with the past, bringing invertedhonji suijaku to maturation as the newYoshida Shintō.[18]
While it is usually claimed that invertedhonji suijaku was a reaction of native cults to the dominance of Buddhism, it also came out of Buddhist intellectualism.[17] The theory is notper se anti-Buddhist and does not question the existence of buddhas but simply seeks to invert the established order of importance betweenkami and buddhas.[19] Why Buddhists should develop such a theory to the detriment of their own divinities is unclear, but it is possible that it was developed by shrine monks, orshasō, who took care of the shrine part of temple-shrine complexes to enhance their status.[17]