本地垂迹（ほんちすいじゃく）とは、仏教が興隆した時代に表れた神仏習合思想の一つで、日本の八百万の神は、実は様々な仏（菩薩や天部なども含む）が化身として日本の地に現れた権現（ごんげん）であるとする考えである。概要本地とは、本来の境地やあり方のことで、垂迹とは、迹（あと）を垂れるという意味で、神仏が現れることを言う。究極の本地は、宇宙の真理そのものである法身であるとし、これを本地法身（ほんちほっしん）という。また権現の権とは「権大納言」などと同じく「臨時の」「仮の」という意味で、仏が神の形を取って仮に現れたことを示す。本地という思想は、仏教が各地で布教されるに、その土地で様々な土着的な宗教を包摂する、という性格をもっていることに起因する。それを表すように、仏教の天部の神々のほとんどはインドのヒンドゥー教を由来とする。またその思想概念は、後期大乗仏教の密教で、大日如来（本地仏）の化身が、不動明王など（加持身）であるという概念を生むことになった。これに対し、垂迹という思想は、中国の『荘子』天運における迹（教化の迹）や、所以迹（教化を成立させている道＝どう）に由来し、西晋の郭象（かくしょう）がこれを註釈した『荘子注』で、これを聖王（内聖外王）の説明において展開させ、“迹”を王者としての統治・主導とし、“所以迹”を本質的な聖人として引用した。そして、これを仏教に取り入れたのが後秦代の僧肇で、その始まりである。僧肇は『注維摩詰経』で、魏の王弼（おうひつ）などが用いた“本末”の思想を引用し、“所以迹”を“本”と言い換えて、“本”を菩薩の不可思議なる解脱（悟りの内容）とし、“迹”を菩薩が衆生を教化するために示現した方便という意味で使用した。僧肇の説は、法華経が久遠実成（釈迦仏は現世で悟ったのではなく久遠の昔に悟っていた）と説くことから、さらに中国天台宗の智顗に影響を与え、法華経の前半部を“迹門”、後半部を“本門”として、教学的解釈が発展した。したがって、本は仏や悟りの本質そのもので、迹は教化・済度のための様々な方便にすぎない、として広く用いられた。日本では、仏教公伝により、奈良時代の物部氏と蘇我氏の対立を見るまでもなく、相互には隔たりがあった。しかし次第にその隔たりがなくなり、仏教側の解釈では、神は迷える衆生の一種で天部の神々と同じであるとした。神を仏の境涯に引き上げようとして納経や度僧が行われたり、仏法の功徳を廻向されて神の身を離脱することが神託に謳われたりした。しかし7世紀後半の天武期において、天皇を中心とする国造りが整備されるに伴い、その氏神であった天照大神を頂点として、それら国造りに重用された神々が民族神へと高められ、仏教側からもその神々に敬意を表して格付けを上げるようになった。実際には、仏の説いた法を味わって仏法を守護する護法善神の仲間であるという解釈により、奈良時代の末期から平安時代にわたり、神に菩薩号を付すまでに至った。民族神の代表格である八幡神が八幡大菩薩などはその典型的な例である。しかしながら、代表的な神でない自然霊や死霊などの小規模な民族神は、この本地垂迹説を用いずに区別した。これはたとえば、権化神（権社神）に対して、実類神（実社神）などがそうである。このため、仏教側では権化神には敬意を表してもよいが、実類神は信奉してはならないという戒めも一部に制定された。これは仏教の一線を守るというあらわれであったと考えられる。この本地垂迹説により、権現造りや本地垂迹の図画なども生まれ、鎌倉中末期には文学でも本地物（ほんじもの）と呼ばれる作品が創作された。鎌倉時代中期になると、逆に仏が神の権化で、神が主で仏が従うと考える神本仏迹説も現れた。仏教優位に不満を持っていた神道側が仏教から独立しようという考えから起こったものである。伊勢外宮の神官である渡会（わたらい）氏は、神話・神事の整理や再編集により、『神道五部書』を作成、伊勢渡会神道の基盤を作った。また、現実を肯定する本覚思想を持つ天台宗の教義を流用し、神道の理論化が試みられ、さらに空海に化託した数種類の理論書も再編され、渡会行忠・家行により、それらが体系づけられた。南北朝時代(日本)から室町時代には、反本地垂迹説がますます主張され、天台宗の側からもこれに同調する者が現れた。慈遍は『旧事本紀玄義』や『豊葦原神風和記』を著して神道に改宗し、良遍(天台宗)は『神代巻私見聞』や『天地麗気記聞書』を著し、この説を支持した。吉田兼倶は、これらを受けて『唯一神道名法要集』を著して、この説を大成させた。しかし鎌倉期の新仏教はこれまで通り、本地垂迹説を支持した。なお、反本地垂迹説とは、昭和時代の学者の命名によるものである。垂迹神と本地仏神の正体とされる仏のことを本地仏という。神々に付会される仏は、宗派、信仰、寺院、神社によって違っている。日本の神の仏号は菩薩が多く、八幡大菩薩は阿弥陀如来であるなど本地仏の仏号と相違することもある。垂迹神と本地仏の一例を以下に示す。アマテラス＝大日如来、十一面観世音菩薩八幡神＝阿弥陀如来＝応神天皇熊野権現＝阿弥陀如来大山咋神＝天照大神＝大日如来市杵島姫＝弁才天愛宕権現＝秋葉権現＝地蔵菩薩スサノオ＝牛頭天王大国主＝大黒天東照大権現（徳川家康）＝薬師如来松尾大社＝薬師如来

honchi-suijaku is one of the thoughts of shinbutsu-shugo ( the amalgamation of buddhism with shinto ) that emerged during the era in which buddhism flourished in japan ; it supports the view that yao yorozu no kami ( eight million gods ) are gongens , the embodiment of various types of buddhas ( including bosatsu ( bodhisattva ) and tenbu ( deva ) ) , which appeared in the land that was japan .summaryhonchi indicates the state of enlightenment , while suijaku , which literally means " bringing down jaku ( ato ) , " indicates the appearance of shinto and buddhist deities .the ultimate honchi is considered to be hossin ( the truth of the universe ) and is therefore called honchi-hossin .as the " gon " of gongen means " provisional " or " temporary , " as shown in " gon-dainagon ( an acting chief councilor of state ) , gongen indicates a buddha that has tentatively appeared in the form of a god .the concept of honchi originated from the inclusive nature of buddhism , which encompassed a wide range of indigenous religions as it spread throughout the region .this is evidenced by the fact that most buddhist tenbu ( deva ) gods originate from hindu , india 's indigenous religion .the thought also gave rise to a theory of esoteric buddhism ( of the later mahayana buddhism ) that kajishin like fudo myo-o ( acala ) is the embodiment of dainichi nyorai ( vairocana ) .on the other hand , the concept of suijaku came from a chinese character , 迹 ( jaku ) , which first appeared in the tenun chapter of " soshi ( zhuang-zi ) " or in its phrase of ' 所以迹 ' ( the path of edification ) , and was later referred to by guo xiang of west jin , the writer of " zhuang-zi commentary " who developed his own theory in the chapter of " seong-wang ( daiseigaio ) " and defined jaku as a royal reign , citing " 所以迹 " as a born saint .it was seng-zhao , of the late qin , who first brought the concept to buddhism .seng-zhao cited , in his writing " chuyuimakitsukyo ( vimalak ? rti sutra commentary ) , " the idea of " honmatsu , " which had been referred to by wang bi of wei , and other scholars replaced the word " 所以迹 " with " 本 " ( hon ) and defined it ( hon ) as an unfathomable nirvana ( enlightenment ) achieved by bodhisattva and " 迹 " ( jaku ) as a means to enlighten people , as used by bodhisattva .his theory , as endorsed by hokekyo ( lotus sutra ) , which supports kuon jitsujo--a view that buddha had been in nirvana long before he was born into this world--further influenced zhiyi of the chinese tendai sect , thus providing a basis for the development of hokekyo 's educational interpretations and the division of its scripture into " jaku-mon " ( the first half ) and " hon-mon " ( the second half ) .this created a widely accepted view that hon is the buddha or enlightenment itself while jaku is simply a means by which to save and enlighten people .in japan , as is evident in the confrontation between the mononobe clan and the soga clan during the nara era , there has been a dividing line between shinto and buddhism since it was officially introduced to japan .however , the line was gradually eroded as the buddhists took the view that shinto gods are a kind of lost , poor people , like the tenbu ( deva ) gods .they tried to raise their status to that of the buddha by leaving copies of sutras at temples or doing doso , officially acknowledging the gods ' achievements and stating in oracles that they would no longer stay as a god thanks to buddha 's good deeds .in the tenmu period of the late seventh century , when the emperor-centered political regime was put in place , the shinto gods that had played important roles in building the country--including amaterasu omikami , the highest ranking ujigami ( local god ) of all--were elevated in status to ethnic gods , and this encouraged buddhists to give them higher ranking as a token of respect .because these gods were considered to be members of the goho zenjin , a group of gods who respected and guarded the buddhist law , some were even granted bosatsu-go ( the title of bodhisattva ) from the end of the nara era through the heian era .a typical example of this is hachimanshin , a famous ethnic god also known as hachiman daibosatsu .however , some low-profile minor ethnic gods , like the spirits of nature and death , to whom the honchi-suijaku theory was not applied , were treated differently .they are , for example , jitsurui no kami ( jitsurui gods ) or jissha no kami ( jissha gods ) , as opposed to gonsha no kami .to make their position clear , some buddhists codified a warning that permitted people to respect gongeshin but not jitsurui no kami .this must have been an intentional effort to keep buddhism separate from shinto .the theory of honji-suijaku affected art and architecture , giving birth to honchi-suijaku zuga ( pictures ) and gongen-zukuri ( buildings ) , and during the middle and end of the kamakura era it affected literature as well , resulting in a series of works called honchimono .by the middle of the kamakura era there appeared a group of people who insisted in the shinpon butsujaku theory that buddhas were in turn the embodiment of shinto gods and that shinto gods were the masters that buddhas followed .this theory was originated by shinto people who had complained about buddhism , which had been dominant over shinto , and wanted shinto to achieve independent status from it .the watarai clan , who had served as priests of gegu ( the outer shrine of ise jingo ) organized and re-edited myths and the records of shinto ceremonies in order to compile the shinto gobusho ( five-volume apologia of shinto ) ; their work laid the foundation for ise watarai shinto .additionally , an attempt was made to theorize shinto by borrowing the doctrine of the tendai sect , which had adopted the reality-affirming hongaku philosophy , and to re-edit several kinds of theory books by falsely attributing them to kukai ; but later these works were organized by yukitada and ieyuki watarai .from the period of the northern and southern courts through the muromachi era , the anti-honchi-suijaku theory increasingly gained ground to the point where some monks of the tendai sect supported it .jihen , the author of " kujihongi gengi " and " toyowashihara shinpuwaki , " converted to shinto ; and ryohen of the tendai sect , the author of " jindai no maki shikenbun " and " tenchi reiki kibunsho , " supported his theory .following these moves , kanetomo yoshida wrote the book titled " yuiitsu shinto myoho yoshu ( the only shinto scripture ) , " making jihen 's theory more complete and comprehensive .however , new buddhist schools that emerged during the kamakura era supported the honchi-suijaku theory as they were supposed to do .note that the anti-honchi-suijaku theory was given its name by the scholars of the showa era .suijakushin ( the god of suijaku ) and honchibutu ( the buddha of honchi )the buddha , the identity of the gods , is called honchibutsu .buddhas that are forcibly linked to shinto gods are different from religion to religion , faith to faith , temple to temple and shrine to shrine .although the most popular buddhist title granted to japanese gods is bosatsu ( bodhisattva ) , some of them--like hachiman daibosatsu , whose honchibutsu title is amida nyorai ( amitabha ) --carry a honchibutsu title that differs from the corresponding buddhist title .the following shows some of the relationships between suijakushin and honchibutsu :amaterasu = dainichi nyorai ( vairocana ) + juichimen kannon bosatsuhachimanshin = amida nyorai ( amitabha ) = emperor ojinkumano gongen = amida nyorai ( amitabha )oyama kui no kami = amaterasu omikami = dainichi nyorai ( vairocana )ichikishima-hime = benzaiten ( sarasvati )atagoo gongen = akiba gongen = jizo bosatsu ( jizo bodhisattva )susanoo = gozu tennookuninushi = daikokuten ( mahakala )tosho daigongen ( ieyasu tokugawa ) = yakushi nyorai ( bhaisaya )matsuo taisha shrine = yakushi nyorai ( bhaisaya )