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Spirit possession

Spirit possession is an unusual or an altered state of consciousness and associated behaviors which are purportedly caused by the control of a human body and its functions by spirits, ghosts, demons, angels, or gods. The concept of spirit possession exists in many cultures and religions, including Buddhism, Christianity, Haitian Vodou, Dominican 21 Divisions, Hinduism, Islam, Wicca, and Southeast Asian, African, and Native American traditions. Depending on the cultural context in which it is found, possession may be considered voluntary or involuntary and may be considered to have beneficial or detrimental effects on the host. The experience of spirit possession sometimes serves as evidence in support of belief in the existence of spirits, deities or demons. In a 1969 study funded by the National Institute of Mental Health, spirit-possession beliefs were found to exist in 74% of a sample of 488 societies in all parts of the world, with the highest numbers of believing societies in Pacific cultures and the lowest incidence among Native Americans of both North and South America. As Pentecostal and Charismatic Christian churches move into both African and Oceanic areas, a merger of belief can take place, with demons becoming representative of the "old" indigenous religions, which Christian ministers attempt to exorcise.

Christianity
From the beginning of Christianity, adherents have held that possession derives from the Devil (i.e. Satan) and demons. In the battle between Satan and Heaven, Satan is believed to engage in "spiritual attacks", including demonic possession, against human beings by the use of supernatural powers to harm them physically or psychologically. Prayer for deliverance, blessings upon the man or woman's house or body, sacraments, and exorcisms are generally used to drive the demon out.

Some theologians, such as Ángel Manuel Rodríguez, say that mediums, like the ones mentioned in Leviticus 20:27, were possessed by demons. Another possible case of demonic possession in the Old Testament includes the false prophets that King Ahab relied upon before re-capturing Ramoth-Gilead in 1 Kings 22. They were described as being empowered by a deceiving spirit.

The New Testament mentions several episodes in which Jesus drove out demons from persons. Whilst most Christians believe that demonic possession is an involuntary affliction, some biblical verses have been interpreted as indicating that possession can be voluntary. For example, Alfred Plummer writes that when Devil entered into Judas Iscariot in John 13:27, this was because Judas had continually agreed to Satan's suggestions to betray Jesus and had wholly submitted to him.

The New Testament indicates that people can be possessed by demons, but that the demons respond and submit to Jesus Christ's authority: "In the synagogue, there was a man possessed by a demon, an evil spirit. He cried out at the top of his voice, 'Ha! What do you want with us, Jesus of Nazareth? Have you come to destroy us? I know who you are—the Holy One of God!' 'Be quiet!' Jesus said sternly. 'Come out of him!' Then the demon threw the man down before them all and came out without injuring him. All the people were amazed and said to each other, 'What is this teaching? With authority and power he gives orders to evil spirits and they come out!' And the news about him spread throughout the surrounding area"

It also indicates that demons can possess animals as in the exorcism of the Gerasene demoniac.

Catholicism
Roman Catholic doctrine states that angels are non-corporeal, spiritual beings with intelligence and will. Fallen angels, or demons, are able to "demonically possess" individuals without the victim's knowledge or consent, leaving them morally blameless.

The Catholic Encyclopedia says that there is only one apparent case of demonic possession in the Old Testament, of King Saul being tormented by an "evil spirit" (1 Samuel 16:14), but this depends on interpreting the Hebrew word "rûah" as implying a personal influence which it may not, so even this example is described as "not very certain". In addition, Saul was only described to be tormented, rather than possessed, and he was relieved from these torments by having David play the lyre to him.

Catholic exorcists differentiate between "ordinary" Satanic/demonic activity or influence (mundane everyday temptations) and "extraordinary" Satanic/demonic activity, which can take six different forms, ranging from complete control by Satan or demons to voluntary submission:
 * 1) Possession, in which Satan or demons take full possession of a person's body without their consent. This possession usually comes as a result of a person's actions; actions that lead to an increased susceptibility to Satan's influence.
 * 2) Obsession, which includes sudden attacks of irrationally obsessive thoughts, usually culminating in suicidal ideation, and which typically influences dreams.
 * 3) Oppression, in which there is no loss of consciousness or involuntary action, such as in the biblical Book of Job in which Job was tormented by Satan through a series of misfortunes in business, material possessions, family, and health.
 * 4) External physical pain caused by Satan or demons.
 * 5) Infestation, which affects houses, objects/things, or animals; and
 * 6) Subjection, in which a person voluntarily submits to Satan or demons.

In the Roman Ritual, true demonic or Satanic possession has been characterized since the Middle Ages, by the following four typical characteristics:
 * 1) Manifestation of superhuman strength.
 * 2) Speaking in tongues or languages that the victim cannot know.
 * 3) Revelation of knowledge, distant or hidden, that the victim cannot know.
 * 4) Blasphemous rage, obscene hand gestures, using profanity and an aversion to holy symbols, names, relics or places.

The New Catholic Encyclopedia states, "Ecclesiastical authorities are reluctant to admit diabolical possession in most cases, because many can be explained by physical or mental illness alone. Therefore, medical and psychological examinations are necessary before the performance of major exorcism. The standard that must be met is that of moral certitude (De exorcismis, 16). For an exorcist to be morally certain, or beyond reasonable doubt, that he is dealing with a genuine case of demonic possession, there must be no other reasonable explanation for the phenomena in question".

Official Catholic doctrine affirms that demonic possession can occur as distinguished from mental illness, but stresses that cases of mental illness should not be misdiagnosed as demonic influence. Catholic exorcisms can occur only under the authority of a bishop and in accordance with strict rules; a simple exorcism also occurs during baptism.

Anglican
The infliction of demonic torment upon an individual has been chronicled in premodern Protestant literature. In 1597, King James discussed four methods of daemonic influence upon an individual in his book Daemonologie:
 * 1) Spectra, being the haunting and troubling of certain houses or solitary places.
 * 2) Obsession, the following and outwardly torment of an individual at diverse hours to either weaken or cast diseases upon the body, as in the Book of Job.
 * 3) Possession, the entrance inwardly into an individual to beget uncontrollable fits, induce blasphemies,
 * 4) Faerie, being the influence those who voluntarily submit to consort, prophesy, or servitude.

King James attested that the symptoms derived from demonic possession could be discernible from natural diseases. He rejected the symptoms and signs prescribed by the Catholic church as vain (e.g. rage begotten from Holy Water, fear of the Cross, etc.) and found the exorcism rites to be troublesome and ineffective to recite. The Rites of the Catholic Church to remedy the torment of demonic spirits were rejected as counterfeit since few possessed could be cured by them. In James' view: "It is easy then to understand that the casting out of Devils, is by virtue of fasting and prayer, and in-calling of the name of God, suppose many imperfections be in the person that is the instrument, as CHRIST himself teaches us (Mat. 7) of the power that false Prophets all have cast out devils".

In medieval Great Britain, the Christian church had offered suggestions on safeguarding one's home. Suggestions ranged from dousing a household with holy water, placing wax and herbs on thresholds to "ward off witches occult", and avoiding certain areas of townships known to be frequented by witches and Devil worshippers after dark. Afflicted persons were restricted from entering the church, but might share the shelter of the porch with lepers and persons of offensive life. After the prayers, if quiet, they might come in to receive the bishop's blessing and listen to the sermon. They were fed daily and prayed over by the exorcists and, in case of recovery, after a fast of from 20 to 40 days, were admitted to the Eucharist, and their names and cures entered in the church records. In 1603, the Church of England forbade its clergy from performing exorcisms because of numerous fraudulent cases of demonic possession.

Baptist
In May 2021, the Baptist Deliverance Study Group of the Baptist Union of Great Britain, a Christian denomination, issued a "warning against occult spirituality following the rise in people trying to communicate with the dead". The commission reported that "becoming involved in activities such as Spiritualism can open up a doorway to great spiritual oppression which requires a Christian rite to set that person free".

In September 2023, Pastor Rick Morrow of Beulah Church in Richland, Missouri gave a sermon in which he presented the cause of autism as, "the devil's attacked them, he's brought this infirmity upon them, he's got them where he wants them". He asserted that the cure for the neurodevelopmental disorder was prayer by claiming to "know a minister who has seen lots of kids that are autistic, that he cast that demon out, and they were healed, and then he had to pray and their brain was rewired and they were fixed." Members of the pastor's community found his comment to be "derogatory toward individuals with certain disabilities." Their public outcry led to Morrow's resignation from the school board on which he was a member.

Evangelical
In both charismatic and evangelical Christianity, exorcisms of demons are often carried out by individuals or groups belong to the deliverance ministries movement. According to these groups, symptoms of such possessions can include chronic fatigue syndrome, homosexuality, addiction to pornography, and alcoholism. The New Testament's description of people who had evil spirits includes a knowledge of future events (Acts 16:16) and great strength (Act 19:13–16), among others, and shows that those with evil spirits can speak of Christ (Mark 3:7–11). Some Evangelical denominations believe that demonic possession is not possible if one has already professed their faith in Christ, because the Holy Spirit already occupies the body and a demon cannot enter.

Islam
Various types of creatures, such as jinn, shayatin, ʻafarit, found within Islamic culture, are often held to be responsible for spirit possession. Spirit possession appears in both Islamic theology and wider cultural tradition.

Although opposed by some Muslim scholars, sleeping near a graveyard or a tomb is believed to enable contact with the ghosts of the dead, who visit the sleeper in dreams and provide hidden knowledge. Possession by ʻafarit (a vengeful ghost) are said to grant the possessed some supernatural powers, but it drives them insane as well.

Jinn are much more physical than spirits. Due to their subtle bodies, which are composed of fire and air (marijin min nar), they are purported to be able to possess the bodies of humans. Such physical intrusion of the jinn is conceptually different from the whisperings of the devils. Since jinn are not necessarily evil, they are distinguished from cultural concepts of possession by devils/demons.

Since such jinn are said to have free will, they can have their own reasons to possess humans and are not necessarily harmful. There are various reasons given as to why a jinn might seek to possess an individual, such as falling in love with them, taking revenge for hurting them or their relatives, or other undefined reasons. At an intended possession, the covenant with the jinn must be renewed. Soothsayers (kāhin pl. kuhhān), would use such possession to gain hidden knowledge. Inspirations from jinn by poets requires neither possession nor obedience to the jinn. Their relationship is rather described as mutual.

The concept of jinn-possession is alien to the Quran and derives from pagan notions. It is widespread among Muslims and also accepted by most Islamic scholars. It is part of the aqida (theological doctrines) in the tradition of Ashari, and the Atharis, such as ibn Taimiyya and ibn Qayyim. Among Maturidites it is debated, as some accept it, but it has been challenged since the early years by Maturidite scholars such as al-Rustughfanī. The Mu'tazila are associated with substituting jinn-possession by devilish-whisperings, denying bodily possession altogether.

In contrast to jinn, the devils (shayatin) are inherently evil. Iblis, the father of the devils, dwells in the fires of hell, although not suffering wherein, he and his children try to draw people into damnation of hell. Devils don't physically possess people, they only tempt humans into sin by following their lower nafs. Hadiths suggest that the devils whisper from within the human body, within or next to the heart, and so "devilish whisperings" (waswās وَسْوَاس ) are sometimes thought of as a kind of possession. Unlike possession by jinn, the whispering of devils affects the soul instead of the body.

Demons (also known as div), though part of the human conception, get stronger through acts of sin. By acts of obedience (to God), they get weaker. Although a human might find pleasure in obeying the demons first, according to Islamic thought, the human soul can only be free if the demons are bound by the spirit (ruh). Sufi literature, as in the writings of Rumi and Attar of Nishapur, pay a lot of attention to how to bind the inner demons. Attar of Nishapur writes: "If you bind the div, you will set out for the royal pavilion with Solomon" and "You have no command over your self's kingdom [body and mind], for in your case the div is in the place of Solomon". He further links the demons to the story alluded in the Quran (38:34) that a demon replaced the prophet Solomon: one must behave like a triumphant 'Solomon' and chain the demons of the nafs or lower self, locking the demon-prince into a 'rock', before the rūḥ (soul) can make the first steps to the Divine.

Judaism
Although forbidden in the Hebrew Bible, magic was widely practiced in the late Second Temple Period and well documented in the period following the destruction of the Temple into the 3rd, 4th, and 5th centuries C.E. Jewish magical papyri were inscriptions on amulets, ostraca and incantation bowls used in Jewish magical practices against shedim and other unclean spirits. According to the Catholic Encyclopedia, Jewish methods of exorcism were described in the Book of Tobias.

In the 16th century, Isaac Luria, a Jewish mystic, wrote about the transmigration of souls seeking perfection. His disciples took his idea a step further, creating the idea of a dybbuk, a soul inhabiting a victim until it had accomplished its task or atoned for its sin. The dybbuk appears in Jewish folklore and literature, as well as in chronicles of Jewish life. In Jewish folklore, a dybbuk is a disembodied spirit that wanders restlessly until it inhabits the body of a living person. The Baal Shem could expel a harmful dybbuk through exorcism.

Possession-trance and adorcism are also engaged with by some Jews. Notably, Ethiopian Jewish women may participate in zār, and Tuisinian Jewish women have a practice called Stambali.

Stambali uses incense, music (traditionally performed by Black musicians from fraternal orders), dance, animal sacrifice, and large spreads of food to induce trance and to appease jinn which may be afflicting someone, and ceremonies may be regularly repeated by that person. Stambali is also sometimes done preventatively as part of wedding, bnei mitzvah, and housewarming festivities to ward away the evil eye. The afflictions of jinn may simply be buildups of emotional stress or more serious illness. During trance, the jinn enter the body, and the participants do not remember what occurred during trance afterwards. If a particular person has needed a Stambali ceremony organized, the jinn afflicting them will be asked what it wants as it possesses them. Usually requests involve clothes and an animal for sacrifice. The atmosphere is festive, and participants wear bright clothes and henna. Aside from musicians, the participants are all women. The dances and lyrics are improvised. Those seen as particularly susceptible to jinn affliction are the victims and perpetrators of aggression, those who are frightened, and those who may have the evil eye directed at them. Showers are also seen as particularly vulnerable places where a jinn may attach themselves to a person.

Democratic Republic of the Congo
Zebola is a women's spirit possession dance ritual practised by certain ethnic groups of the Democratic Republic of the Congo. It is believed to have therapeutic qualities and has been noted in the West as a traditional form of psychotherapy.

It originated among the Mongo people but is also practised among various ethnic groups in Kinshasa.

Ethiopia
Among the Gurage people of Ethiopia, spirit possession is a common belief. William A. Shack postulated that it is caused by Gurage cultural attitudes about food and hunger, while they have a plentiful food supply, cultural pressures that force the Gurage to either share it to meet social obligations, or hoard it and eat it secretly cause feelings of anxiety. Distinctions are drawn between spirits that strictly possess men, spirits that possess women, and spirits that possess victims of either sex. A ritual illness that only affects men is believed to be caused by a spirit called awre. This affliction presents itself by loss of appetite, nausea, and attacks from severe stomach pains. If it persists, the victim may enter a trance-like stupor, in which he sometimes regains consciousness long enough to take food and water. Breathing is often labored. Seizures and trembling overcome the patient, and in extreme cases, partial paralysis of the extremities.

If the victim does not recover naturally, a traditional healer, or sagwara, is summoned. Once the sagwara has determined the spirit's name through the use of divination, he prescribes a routine formula to exorcise the spirit. This is not a permanent cure, it merely allows the victim to form a relationship with the spirit while subject to chronic repossession, which is treated by repeating the formula. This formula involves the preparation and consumption of a dish of ensete, butter, and red pepper. During this ritual, the victim's head is covered with a drape, and he eats the ensete ravenously while other ritual participants participate by chanting. The ritual ends when the possessing spirit announces that it is satisfied. Shack notes that the victims are overwhelmingly poor men, and that women are not as food-deprived as men, due to ritual activities that involve food redistribution and consumption. Shack postulates that the awre serves to bring the possessed man to the center of social attention, and to relieve his anxieties over his inability to gain prestige from redistributing food, which is the primary way in which Gurage men gain status in their society.

The belief in spirit possession is part of the native culture of the Sidama people of southwest Ethiopia. Anthropologists Irene and John Hamer postulated that it is a form of compensation for being deprived within Sidama society, although they do not draw from I.M. Lewis (see Cultural anthropology section under Scientific views). The majority of the possessed are women whose spirits demand luxury goods to alleviate their condition, but men can be possessed as well. Possessed individuals of both sexes can become healers due to their condition. Hamer and Hamer suggest that this is a form of compensation among deprived men in the deeply competitive society of the Sidama, for if a man cannot gain prestige as an orator, warrior, or farmer, he may still gain prestige as a spirit healer. Women are sometimes accused of faking possession, but men never are.

East Africa
Kenya

 * The Digo people of Kenya refer to the spirits that supposedly possess them as shaitani. These shaitani typically demand luxury items to make the patient well again. Despite the fact that men sometimes accuse women of faking the possessions in order to get luxury items, attention, and sympathy, they do generally regard spirit possession as a genuine condition and view victims of it as being ill through no fault of their own. Other men suspect women of actively colluding with spirits in order to be possessed.
 * The Giriama people of coastal Kenya believe in spirit possession.

Mayote
 * In Mayotte, approximately 25% of the adult population, and five times as many women as men, enter trance states in which they are supposedly possessed by certain identifiable spirits who maintain stable and coherent identities from one possession to the next.

Mozambique
 * In Mozambique, a new belief in spirit possession appeared after the Mozambican Civil War. These spirits, called gamba, are said to be identified as dead soldiers, and allegedly overwhelmingly possess women. Prior to the war, spirit possession was limited to certain families and was less common.

Uganda
 * In Uganda, a woman named Alice Auma was reportedly possessed by the spirit of a male Italian soldier named Lakwena ('messenger'). She ultimately led a failed insurrection against governmental forces.

Tanzania
 * The Sukuma people of Tanzania believe in spirit possession.
 * A now-extinct spirit possession cult existed among the Hadimu women of Zanzibar, revering a spirit called kitimiri. This cult was described in an 1869 account by a French missionary. The cult faded by the 1920s and was virtually unknown by the 1960s.

Southern Africa

 * A belief in spirit possession appears among the Xesibe, a Xhosa-speaking people from Transkei, South Africa. The majority of the supposedly possessed are married women. The condition of spirit possession among them is called intwaso. Those who develop the condition of intwaso are regarded as having a special calling to divine the future. They are first treated with sympathy, and then with respect as they allegedly develop their abilities to foretell the future.

West Africa

 * One religion among Hausa people of West Africa is that of Hausa animism, in which belief in spirit possession is prevalent.

African diasporic traditions
In many of the African diaspora religions possessing spirits are not necessarily harmful or evil, but are rather seeking to rebuke misconduct in the living. Possession by a spirit in the African diaspora and traditional African religions can result in healing for the person possessed and information gained from possession as the spirit provides knowledge to the one they possessed.

Haitian Vodou
In Haitian Vodou and related African diaspora religions, one way that those who participate or practice can have a spiritual experience is by being possessed by the Loa (or lwa). When the Loa descends upon a practitioner, the practitioner's body is being used by the spirit, according to the tradition. Some spirits are believed to be able to give prophecies of upcoming events or situations pertaining to the possessed one, also called a Chwal or the "Horse of the Spirit". Practitioners describe this as a beautiful but very tiring experience. Most people who are possessed by the spirit describe the onset as a feeling of blackness or energy flowing through their body.

Umbanda
The concept of spirit possession is also found in Umbanda, an Afro-Brazilian folk religion. According to tradition, one such possessing spirit is Pomba Gira, who possesses both women and males.

Hoodoo
The culture of Hoodoo was created by African-Americans. There are regional styles to this tradition, and as African-Americans traveled, the tradition of Hoodoo changed according to African-Americans' environment. Hoodoo includes reverence to ancestral spirits, African-American quilt making, herbal healing, Bakongo and Igbo burial practices, Holy Ghost shouting, praise houses, snake reverence, African-American churches, spirit possession, some Nkisi practices, Black Spiritual churches, Black theology, the ring shout, the Kongo cosmogram, Simbi water spirits, graveyard conjuring, the crossroads spirit, making conjure canes, incorporating animal parts, pouring of libations, Bible conjuring, and conjuring in the African-American tradition. In Hoodoo, people become possessed by the Holy Ghost. Spirit possession in Hoodoo was influenced by West African Vodun spirit possession. As Africans were enslaved in the United States, the Holy Spirit (Holy Ghost) replaced the African gods during possession. "Spirit possession was reinterpreted in Christian terms." In African-American churches this is called being filled with the Holy Ghost. "Walter Pitts (1993) has demonstrated the modern importance of 'possession' within African- American Baptist ritual, tracing the origins of the ecstatic state (often referred to as 'getting the spirit') to African possessions." Church members in Black Spiritual churches become possessed by spirits of deceased family members, the Holy Spirit, Christian saints, and other biblical figures from the Old and New Testament of the Bible. It is believed when people become possessed by these spirits they gain knowledge and wisdom and act as intercessors between people and God. William Edward Burghardt Du Bois (W. E. B. Du Bois) studied African-American churches in the early twentieth century. Du Bois asserts that the early years of the Black church during slavery on plantations was influenced by Voodooism. Through counterclockwise circle dancing, ring shouters built up spiritual energy that resulted in the communication with ancestral spirits, and led to spirit possession. Enslaved African Americans performed the counterclockwise circle dance until someone was pulled into the center of the ring by the spiritual vortex at the center. The spiritual vortex at the center of the ring shout was a sacred spiritual realm. The center of the ring shout is where the ancestors and the Holy Spirit reside at the center. The Ring Shout (a sacred dance in Hoodoo) in Black churches results in spirit possession. The Ring Shout is a counterclockwise circle dance with singing and clapping that results in possession by the Holy Spirit. It is believed when people become possessed by the Holy Spirit their hearts become filled with the Holy Ghost which purifies their heart and soul from evil and replace it with joy. The Ring Shout in Hoodoo was influenced by the Kongo cosmogram a sacred symbol of the Bantu-Kongo people in Central Africa. It symbolizes the cyclical nature of life of birth, life, death, and rebirth (reincarnation of the soul). The Kongo cosmogram also symbolizes the rising and setting of the sun, the sun rising in the east and setting in the west that is counterclockwise, which is why ring shouters dance in a circle counterclockwise to invoke the spirit.

Yahwism
There are indications that trance-related practices might have played a role in the prophetic experiences of adherents of Yahwism. According to Martti Nissinen, Yahwist prophets may have received messages from the different gods and goddesses in the Yahwist Pantheon through a state of trance possession. This theory can be reconstructed from Sumerian Mythology, a similar theology to that of Yahwism, where the standard prophetic designations in the Akkadian language, muḫḫûm/muḫḫūtum (masc./fem., Old Babylonian) and maḫḫû/maḫḫūtu (masc./fem., Neo-Assyrian), are derived from the Akkadian verb maḫû "to become crazy, to go into a frenzy." According to bible scholar Simon B. Parker, trance rituals may have occurred such as nudity or a less extreme alternative, a trance where the person to enter trance receives the god or spirit into their body.

Further according to Nissinen, the Hebrew Bible, may contain evidence that trance-related practices may have been the origins of the Jewish traditions of prophetic messages. However, these instances may have been limited, with trance instead being a way of confirming divine appointment to a leadership position.

Nissinen also recorded that music was an essential part to these trance-ceremonies in the Ancient Near-East and so it can be reconstructed it could have been found in Yahwism. Instruments such as the tambourine, harps, lyres, and flutes may have been utilized, as those were common instruments in Ancient Israel. Along with music, incense may have also been used, either as an offering, or to be used as an entheogen, or possibly as both.

Exorcisms were also common. They can be reconstructed from both Medieval Jewish texts and texts from neighboring ancient cultures that practiced exorcisms. Exorcists acting almost like shamans would do rituals to exorcise one of a "demon" or evil spirit. According to Gina Konstantopoulos, a figure named an "Āshipu" acted as an exorcist in Mesopotamia and were trained in many fields of occultism, priesthood and herbalism. As amulets (called teraphim) were also used in Yahwism to ward off evil spirits, it may also be reconstructed that there were people in Ancient Israel who acted as exorcists or shamans who would do specific rituals to ward off evil spirits. As mentioned previously, these may have included music, incense, prayers, and trance-rituals. According to Reimund Leicht, formulae was used ward off the evil, along with ritualistic sacrifices.

Buddhism
According to the Indian medical literature and Tantric Buddhist scriptures, most of the "seizers", or those that threaten the lives of young children, appear in animal form: cow, lion, fox, monkey, horse, dog, pig, cat, crow, pheasant, owl, and snake. Apart from these "nightmare shapes", the impersonation or incarnation of animals can in some circumstances also be highly beneficial, according to Michel Strickmann.

Ch'i Chung-fu, a Chinese gynecologist writing early in the 13th century, wrote that in addition to five sorts of falling frenzy classified according to their causative factors, there were also four types of other frenzies distinguished by the sounds and movements given off by the victim during his seizure: cow, horse, pig, and dog frenzies.

In Buddhism, a māra, sometimes translated as "demon", can either be a being suffering in the hell realm or a delusion. Before Siddhartha became Gautama Buddha, He was challenged by Mara, the embodiment of temptation, and overcame it. In traditional Buddhism, four forms of māra are enumerated:
 * Kleśa-māra, or  māra as the embodiment of all unskillful emotions, such as greed, hate, and delusion.
 * Mṛtyu-māra, or māra as death.
 * Skandha-māra, or māra as metaphor for the entirety of conditioned existence.
 * Devaputra-māra, the deva of the sensuous realm, who tried to prevent Gautama Buddha from attaining liberation from the cycle of rebirth on the night of the Buddha's enlightenment.

It is believed that a māra will depart to a different realm once it is appeased.

East Asia
Certain sects of Taoism, Korean shamanism, Shinto, some Japanese new religious movements, and other East Asian religions feature the idea of spirit possession. Some sects feature shamans who supposedly become possessed; mediums who allegedly channel beings' supernatural power; or enchanters are said to imbue or foster spirits within objects, like samurai swords. The Hong Kong film Super Normal II (大迷信, 1993) shows the true famous story of a young lady in Taiwan who possesses the dead body of a married woman to live her pre-determined remaining life. She is still serving in the Zhen Tian Temple in Yunlin County.

Background
China is a country where 73.56% of the population is defined as Chinese folk religion/unaffiliated (nonreligion). Therefore, the Chinese population's knowledge of spirit possession is not majorly obtained from religion. Instead, the concept is spread through fairy tales/folk tales and literary works of its traditional culture. In essence, the concept of soul possession has penetrated into all aspects of Chinese life, from people's superstitions, folk taboos, and funeral rituals, to various ghost-themed literary works, and has continued to spread to people's lives today.

Development
Spirit possession in China was prominent until the Communist takeover in the 1950s and most of the data gathered on this topic will be from the late 18th century. Some Chinese believe that illnesses to man is due to the possession of an evil yin spirit (kuei). These evil spirits become such when the deceased are not worshiped by the family, they have died unexpectedly, or did not follow Confucius's ideals of filial piety and ancestral reverence accordingly. These evil spirits cause unexplainable disasters, agricultural shocks and possessions. Disease is the cause of the supernatural where they do not have control over. Usually in the writings about this, the healers are the ones being described with detail, not so much the patient. Magical practices are sometimes what spirit possession is referred to as. It is very hard to distinguish between the religion, magic and local traditions. This is because many times, all three are fused together, so sometimes trying to distinguish between them is hard.

Shaman
Another type of spirit possession works through a shaman, a prophet, healer and religious figure with the power to partially control spirits and communicate for them. Messages, remedies and even oracles are delivered through the shaman. This is sometimes used by people who would like to become important figures. Usually, shamans give guidance that reflects the customer's existing values.

Yin-yang theory
The yin-yang theory is one of the most important bases and components of Chinese traditional culture. The yin-yang theory has penetrated into various traditional Chinese cultural things including calendar, astronomy, meteorology, Chinese medicine, martial arts, calligraphy, architecture, religion, feng shui, divination, etc. The yin-yang theory also applies to spirit possession. In general, one is considered to be "weak", when the yin and yang in the body are imbalanced, especially when the yin is on the dominant side. The spirits, which are categorized as the yin side, will then take control of these individuals with the imbalanced and yin-dominant situation more easily.
 * Shi (Chinese ancestor veneration)
 * Shamanism of the Solon People (Inner Mongolia)
 * Tangki

Japan

 * Misaki

Ayurveda
Bhūtavidyā, the exorcism of possessing spirits, is traditionally one of the eight limbs of Ayurveda.

Rajasthan
The concept of spirit possession exists in the culture of modern Rajasthan. Some of the spirits allegedly possessing Rajasthanis are seen as good and beneficial, while others are seen as malevolent. The good spirits are said to include murdered royalty, the underworld god Bhaironji, and Muslim saints and fakirs. Bad spirits are believed to include perpetual debtors who die in debt, stillborn infants, deceased widows, and foreign tourists. The supposedly possessed individual is referred to as a ghorala, or "mount". Possession, even if by a benign spirit, is regarded as undesirable, as it is seen to entail loss of self-control, and violent emotional outbursts.

Tamil Nadu
Tamil women in India are said to experience possession by peye spirits. According to tradition, these spirits overwhelmingly possess new brides, are usually identified as the ghosts of young men who died while romantically or sexually frustrated, and are ritually exorcised.

Sri Lanka
The Coast Veddas, a social group within the minority group of Sri Lankan Tamil people in Eastern Province, Sri Lanka, enter trances during religious festivals in which they are regarded as being possessed by a spirit. Although they speak a dialect of Tamil, during trances they will sometimes use a mixed language that contains words from the Vedda language.

Indonesia
In Bali, the animist traditions of the island include a practice called sanghyang, induction of voluntary possession trance states for specific purposes. Roughly similar to voluntary possession in Vaudon (Voodoo), sanghyang is considered a sacred state in which hyangs (deities) or helpful spirits temporarily inhabit the bodies of participants. The purpose of sanghyang is believed to be to cleanse people and places of evil influences and restore spiritual balance. Thus, it is often referred to as an exorcism ceremony. In Sulawesi, the women of the Bonerate people of Sulawesi practice a possession-trance ritual in which they smother glowing embers with their bare feet at the climax. The fact that they are not burned in the process is considered proof of the authenticity of the possession.

Influenced by the religion of Islam, among the several spirits in Indonesian belief are demons (setan), composed of fire, prone to anger and passion. They envy humans for their physical body, and try to gain control of it. When they assault a human, they would intrude their mind, trying to displace the human spirit. The human's mind would adapt to the passions of anger, violence, irrationality and greed, the intruding demon is composed of. The demon is believed to alter the person, giving him supernatural attributes, like strength of many men, ability to appear in more than one place, or assume the form of an animal, such as a tiger or a pig, or to kill without touching. Others become lunatics, resembling epilepsy. In extreme cases, the presence of the demon may alter the condition of the body, matching its own spiritual qualities, turning into a raksasha.

Malaysia
Female workers in Malaysian factories have allegedly become possessed by spirits, and factory owners generally regard it as mass hysteria and an intrusion of irrational and archaic beliefs into a modern setting. Anthropologist Aihwa Ong noted that spirit possession beliefs in Malaysia were typically held by older, married women, whereas the female factory workers are typically young and unmarried. She connects this to the rapid industrialization and modernization of Malaysia. Ong argued that spirit possession is a traditional way of rebelling against authority without punishment, and suggests that it is a means of protesting the untenable working conditions and sexual harassment that the women were compelled to endure.

Indo-Caribbean Shaktism
In Indo-Caribbean Madrasi Religion, a state of trance-possession known as "Sami Aduthal" in Tamil and as a "manifestation" in English occurs whence a devotee enters a trance state after praying. It is an essential part to Indo-Caribbean Shakti ceremonies, being accompanied by Tappu drumming, the singing of devotional songs, and the drumming of Udukai drums.

Ceremonies called Pujas often include the drumming of three to five tappu to invoke the deity to the space. Then, the head pujari receives the God or Goddess into their body, acting as a medium. A mixture of water, turmeric powder, and neem leaves are poured onto the medium, as it is believed that the God's energy heats up the body while the water and turmeric with the neem leaves cools it down again. Puja services are often held once a week.

Melanesia
The Urapmin people of the New Guinea Highlands practice a form of group possession known as the "spirit disco" (spirit disko). Men and women gather in church buildings, dancing in circles and jumping up and down while women sing Christian songs; this is called "pulling the [Holy] spirit" (pulim spirit, Urap: Sinik dagamin). The songs' melodies are borrowed from traditional women's songs sung at drum dances (Urap: wat dalamin), and the lyrics are typically in Telefol or other Mountain Ok languages. If successful, some dancers will "get the spirit" (kisim spirit), flailing wildly and careening about the dance floor. After an hour or more, those possessed will collapse, the singing will end, and the spirit disco will end with a prayer and, if there is time, a Bible reading and sermon. The body is believed to normally be "heavy" (ilum) with sin, and possession is the process of the Holy Spirit throwing the sins from one's body, making the person "light" (fong) again. This is a completely new ritual for the Urapmin, who have no indigenous tradition of spirit-possession.

Micronesia
The concept of spirit possession appears in Chuuk State, one of the four states of Federated States of Micronesia. Although Chuuk is an overwhelmingly Christian society, traditional beliefs in spirit possession by the dead still exist, usually held by women, and "events" are usually brought on by family conflicts. The supposed spirits, speaking through the women, typically admonish family members to treat each other better.

Italian folk magic
In traditional Italian folk magic spirit possessions are not uncommon. It is known in this culture that a person may be possessed by multiple entities at once. The way to be rid of the spirit(s) would be to call for a curatore, guaritore or pratico which all translate to healer or knowledgeable one from Italian. These healers would perform sacred rituals to be rid of the spirits; the rituals are passed down through generations and vary based on the region in Italy. It is said that for many Italian rituals specifically those to be rid of negative spirits, that the information may only be shared on Christmas Eve (specifically for il malocchio). If the family is religious they may even call in a priest to perform a traditional catholic exorcism on the spirit(s).

Shamanic traditions
Shamanism is a religious practice that involves a practitioner who is believed to interact with a spirit world through altered states of consciousness, such as trance. The goal of this is usually to direct these spirits or spiritual energies into the physical world, for healing or another purpose.

Wicca
Wiccans believe in voluntary possession by the Goddess, connected with the sacred ceremony of Drawing Down the Moon. The high priestess solicits the Goddess to possess her and speak through her.

Cultural anthropology
The works of Jean Rouch, Germaine Dieterlen, and Marcel Griaule have been extensively cited in research studies on possession in Western Africa that extended to Brazil and North America due to the slave trade.

The anthropologist I.M. Lewis noted that women are more likely to be involved in spirit possession cults than men are, and postulated that such cults act as a means of compensation for their exclusion from other spheres within their respective cultures.

Physical anthropology
Anthropologists Alice B. Kehoe and Dody H. Giletti argued that the reason that women are more commonly seen in Afro-Eurasian spirit possession cults is because of deficiencies in thiamine, tryptophan-niacin, calcium, and vitamin D. They argued that a combination of poverty and diet cause this problem, and that it is exacerbated by the strains of pregnancy and lactation. They postulated that the involuntary symptoms of these deficiencies affecting their nervous systems have been institutionalized as spirit possession.

Medicine and psychology
Spirit possession of any kind, including demonic, is just one psychiatric or medical diagnosis recognized by the DSM-5 or the ICD-10: "F44.3 Trance and possession disorders". In clinical psychiatry, trance and possession disorders are defined as "states involving a temporary loss of the sense of personal identity and full awareness of the surroundings" and generally classed as a type of dissociative disorder.

People alleged to be possessed by spirits sometimes exhibit symptoms similar to those associated with mental illnesses such as psychosis, catatonia, mania, Tourette's syndrome, epilepsy, schizophrenia, or dissociative identity disorder, including involuntary, uncensored behavior, and an extra-human, extra-social aspect to the individual's actions. It is not uncommon to ascribe the experience of sleep paralysis to demonic possession, although it's not a physical or mental illness. Studies have found that alleged demonic possessions can be related to trauma.

In entry article on dissociative identity disorder, the DSM-5 states, "possession-form identities in dissociative identity disorder typically manifest as behaviors that appear as if a 'spirit,' supernatural being, or outside person has taken control such that the individual begins speaking or acting in a distinctly different manner". The symptoms vary across cultures. The DSM-5 indicates that personality states of dissociative identity disorder may be interpreted as possession in some cultures, and instances of spirit possession are often related to traumatic experiences—suggesting that possession experiences may be caused by mental distress. In cases of dissociative identity disorder in which the alter personality is questioned as to its identity, 29 percent are reported to identify themselves as demons. A 19th century term for a mental disorder in which the patient believes that they are possessed by demons or evil spirits is demonomania or cacodemonomanis.

Some have expressed concern that belief in demonic possession can limit access to health care for the mentally ill.

Purported demonic possessions
In chronological order:

title: Spirit possession


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General equilibrium theory

In economics, general equilibrium theory attempts to explain the behavior of supply, demand, and prices in a whole economy with several or many interacting markets, by seeking to prove that the interaction of demand and supply will result in an overall general equilibrium. General equilibrium theory contrasts with the theory of partial equilibrium, which analyzes a specific part of an economy while its other factors are held constant. In general equilibrium, constant influences are considered to be noneconomic, or in other words, considered to be beyond the scope of economic analysis. The noneconomic influences may change given changes in the economic factors however, and therefore the prediction accuracy of an equilibrium model may depend on the independence of the economic factors from noneconomic ones.

General equilibrium theory both studies economies using the model of equilibrium pricing and seeks to determine in which circumstances the assumptions of general equilibrium will hold. The theory dates to the 1870s, particularly the work of French economist Léon Walras in his pioneering 1874 work Elements of Pure Economics. The theory reached its modern form with the work of Lionel W. McKenzie (Walrasian theory), Kenneth Arrow and Gérard Debreu (Hicksian theory) in the 1950s.

Overview
Broadly speaking, general equilibrium tries to give an understanding of the whole economy using a "bottom-up" approach, starting with individual markets and agents. Therefore, general equilibrium theory has traditionally been classified as part of microeconomics. The difference is not as clear as it used to be, since much of modern macroeconomics has emphasized microeconomic foundations, and has constructed general equilibrium models of macroeconomic fluctuations. General equilibrium macroeconomic models usually have a simplified structure that only incorporates a few markets, like a "goods market" and a "financial market". In contrast, general equilibrium models in the microeconomic tradition typically involve a multitude of different goods markets. They are usually complex and require computers to calculate numerical solutions.

In a market system the prices and production of all goods, including the price of money and interest, are interrelated. A change in the price of one good, say bread, may affect another price, such as bakers' wages. If bakers don't differ in tastes from others, the demand for bread might be affected by a change in bakers' wages, with a consequent effect on the price of bread. Calculating the equilibrium price of just one good, in theory, requires an analysis that accounts for all of the millions of different goods that are available. It is often assumed that agents are price takers, and under that assumption two common notions of equilibrium exist: Walrasian, or competitive equilibrium, and its generalization: a price equilibrium with transfers.

Walrasian equilibrium
The first attempt in neoclassical economics to model prices for a whole economy was made by Léon Walras. Walras' Elements of Pure Economics provides a succession of models, each taking into account more aspects of a real economy (two commodities, many commodities, production, growth, money). Some think Walras was unsuccessful and that the later models in this series are inconsistent.

In particular, Walras's model was a long-run model in which prices of capital goods are the same whether they appear as inputs or outputs and in which the same rate of profits is earned in all lines of industry. This is inconsistent with the quantities of capital goods being taken as data. But when Walras introduced capital goods in his later models, he took their quantities as given, in arbitrary ratios. (In contrast, Kenneth Arrow and Gérard Debreu continued to take the initial quantities of capital goods as given, but adopted a short run model in which the prices of capital goods vary with time and the own rate of interest varies across capital goods.)

Walras was the first to lay down a research program widely followed by 20th-century economists. In particular, the Walrasian agenda included the investigation of when equilibria are unique and stable— Walras' Lesson 7 shows neither uniqueness, nor stability, nor even existence of an equilibrium is guaranteed. Walras also proposed a dynamic process by which general equilibrium might be reached, that of the tâtonnement or groping process.

The tâtonnement process is a model for investigating stability of equilibria. Prices are announced (perhaps by an "auctioneer"), and agents state how much of each good they would like to offer (supply) or purchase (demand). No transactions and no production take place at disequilibrium prices. Instead, prices are lowered for goods with positive prices and excess supply. Prices are raised for goods with excess demand. The question for the mathematician is under what conditions such a process will terminate in equilibrium where demand equates to supply for goods with positive prices and demand does not exceed supply for goods with a price of zero. Walras was not able to provide a definitive answer to this question (see Unresolved Problems in General Equilibrium below).

Marshall and Sraffa
In partial equilibrium analysis, the determination of the price of a good is simplified by just looking at the price of one good, and assuming that the prices of all other goods remain constant. The Marshallian theory of supply and demand is an example of partial equilibrium analysis. Partial equilibrium analysis is adequate when the first-order effects of a shift in the demand curve do not shift the supply curve. Anglo-American economists became more interested in general equilibrium in the late 1920s and 1930s after Piero Sraffa's demonstration that Marshallian economists cannot account for the forces thought to account for the upward-slope of the supply curve for a consumer good.

If an industry uses little of a factor of production, a small increase in the output of that industry will not bid the price of that factor up. To a first-order approximation, firms in the industry will experience constant costs, and the industry supply curves will not slope up. If an industry uses an appreciable amount of that factor of production, an increase in the output of that industry will exhibit increasing costs. But such a factor is likely to be used in substitutes for the industry's product, and an increased price of that factor will have effects on the supply of those substitutes. Consequently, Sraffa argued, the first-order effects of a shift in the demand curve of the original industry under these assumptions includes a shift in the supply curve of substitutes for that industry's product, and consequent shifts in the original industry's supply curve. General equilibrium is designed to investigate such interactions between markets.

Continental European economists made important advances in the 1930s. Walras' arguments for the existence of general equilibrium often were based on the counting of equations and variables. Such arguments are inadequate for non-linear systems of equations and do not imply that equilibrium prices and quantities cannot be negative, a meaningless solution for his models. The replacement of certain equations by inequalities and the use of more rigorous mathematics improved general equilibrium modeling.

Modern concept of general equilibrium in economics
The modern conception of general equilibrium is provided by the Arrow–Debreu–McKenzie model, developed jointly by Kenneth Arrow, Gérard Debreu, and Lionel W. McKenzie in the 1950s. Debreu presents this model in Theory of Value (1959) as an axiomatic model, following the style of mathematics promoted by Nicolas Bourbaki. In such an approach, the interpretation of the terms in the theory (e.g., goods, prices) are not fixed by the axioms.

Three important interpretations of the terms of the theory have been often cited. First, suppose commodities are distinguished by the location where they are delivered. Then the Arrow-Debreu model is a spatial model of, for example, international trade.

Second, suppose commodities are distinguished by when they are delivered. That is, suppose all markets equilibrate at some initial instant of time. Agents in the model purchase and sell contracts, where a contract specifies, for example, a good to be delivered and the date at which it is to be delivered. The Arrow–Debreu model of intertemporal equilibrium contains forward markets for all goods at all dates. No markets exist at any future dates.

Third, suppose contracts specify states of nature which affect whether a commodity is to be delivered: "A contract for the transfer of a commodity now specifies, in addition to its physical properties, its location and its date, an event on the occurrence of which the transfer is conditional. This new definition of a commodity allows one to obtain a theory of [risk] free from any probability concept..."

These interpretations can be combined. So the complete Arrow–Debreu model can be said to apply when goods are identified by when they are to be delivered, where they are to be delivered and under what circumstances they are to be delivered, as well as their intrinsic nature. So there would be a complete set of prices for contracts such as "1 ton of Winter red wheat, delivered on 3rd of January in Minneapolis, if there is a hurricane in Florida during December". A general equilibrium model with complete markets of this sort seems to be a long way from describing the workings of real economies, however, its proponents argue that it is still useful as a simplified guide as to how real economies function.

Some of the recent work in general equilibrium has in fact explored the implications of incomplete markets, which is to say an intertemporal economy with uncertainty, where there do not exist sufficiently detailed contracts that would allow agents to fully allocate their consumption and resources through time. While it has been shown that such economies will generally still have an equilibrium, the outcome may no longer be Pareto optimal. The basic intuition for this result is that if consumers lack adequate means to transfer their wealth from one time period to another and the future is risky, there is nothing to necessarily tie any price ratio down to the relevant marginal rate of substitution, which is the standard requirement for Pareto optimality. Under some conditions the economy may still be constrained Pareto optimal, meaning that a central authority limited to the same type and number of contracts as the individual agents may not be able to improve upon the outcome, what is needed is the introduction of a full set of possible contracts. Hence, one implication of the theory of incomplete markets is that inefficiency may be a result of underdeveloped financial institutions or credit constraints faced by some members of the public. Research still continues in this area.

Properties and characterization of general equilibrium
Basic questions in general equilibrium analysis are concerned with the conditions under which an equilibrium will be efficient, which efficient equilibria can be achieved, when an equilibrium is guaranteed to exist and when the equilibrium will be unique and stable.

First Fundamental Theorem of Welfare Economics
The First Fundamental Welfare Theorem asserts that market equilibria are Pareto efficient. In other words, the allocation of goods in the equilibria is such that there is no reallocation which would leave a consumer better off without leaving another consumer worse off. In a pure exchange economy, a sufficient condition for the first welfare theorem to hold is that preferences be locally nonsatiated. The first welfare theorem also holds for economies with production regardless of the properties of the production function. Implicitly, the theorem assumes complete markets and perfect information. In an economy with externalities, for example, it is possible for equilibria to arise that are not efficient.

The first welfare theorem is informative in the sense that it points to the sources of inefficiency in markets. Under the assumptions above, any market equilibrium is tautologically efficient. Therefore, when equilibria arise that are not efficient, the market system itself is not to blame, but rather some sort of market failure.

Second Fundamental Theorem of Welfare Economics
Even if every equilibrium is efficient, it may not be that every efficient allocation of resources can be part of an equilibrium. However, the second theorem states that every Pareto efficient allocation can be supported as an equilibrium by some set of prices. In other words, all that is required to reach a particular Pareto efficient outcome is a redistribution of initial endowments of the agents after which the market can be left alone to do its work. This suggests that the issues of efficiency and equity can be separated and need not involve a trade-off. The conditions for the second theorem are stronger than those for the first, as consumers' preferences and production sets now need to be convex (convexity roughly corresponds to the idea of diminishing marginal rates of substitution i.e. "the average of two equally good bundles is better than either of the two bundles").

Existence
Even though every equilibrium is efficient, neither of the above two theorems say anything about the equilibrium existing in the first place. To guarantee that an equilibrium exists, it suffices that consumer preferences be strictly convex. With enough consumers, the convexity assumption can be relaxed both for existence and the second welfare theorem. Similarly, but less plausibly, convex feasible production sets suffice for existence; convexity excludes economies of scale.

Proofs of the existence of equilibrium traditionally rely on fixed-point theorems such as Brouwer fixed-point theorem for functions (or, more generally, the Kakutani fixed-point theorem for set-valued functions). See Competitive equilibrium. The proof was first due to Lionel McKenzie, and Kenneth Arrow and Gérard Debreu. In fact, the converse also holds, according to Uzawa's derivation of Brouwer's fixed point theorem from Walras's law. Following Uzawa's theorem, many mathematical economists consider proving existence a deeper result than proving the two Fundamental Theorems.

Another method of proof of existence, global analysis, uses Sard's lemma and the Baire category theorem; this method was pioneered by Gérard Debreu and Stephen Smale.

Nonconvexities in large economies
Starr (1969) applied the Shapley–Folkman–Starr theorem to prove that even without convex preferences there exists an approximate equilibrium. The Shapley–Folkman–Starr results bound the distance from an "approximate" economic equilibrium to an equilibrium of a "convexified" economy, when the number of agents exceeds the dimension of the goods. Following Starr's paper, the Shapley–Folkman–Starr results were "much exploited in the theoretical literature", according to Guesnerie, who wrote the following: some key results obtained under the convexity assumption remain (approximately) relevant in circumstances where convexity fails. For example, in economies with a large consumption side, nonconvexities in preferences do not destroy the standard results of, say Debreu's theory of value. In the same way, if indivisibilities in the production sector are small with respect to the size of the economy, [. . . ] then standard results are affected in only a minor way. To this text, Guesnerie appended the following footnote: The derivation of these results in general form has been one of the major achievements of postwar economic theory. In particular, the Shapley-Folkman-Starr results were incorporated in the theory of general economic equilibria  and in the theory of market failures and of public economics.

Uniqueness
Although generally (assuming convexity) an equilibrium will exist and will be efficient, the conditions under which it will be unique are much stronger. The Sonnenschein–Mantel–Debreu theorem, proven in the 1970s, states that the aggregate excess demand function inherits only certain properties of individual's demand functions, and that these (continuity, homogeneity of degree zero, Walras' law and boundary behavior when prices are near zero) are the only real restriction one can expect from an aggregate excess demand function. Any such function can represent the excess demand of an economy populated with rational utility-maximizing individuals.

There has been much research on conditions when the equilibrium will be unique, or which at least will limit the number of equilibria. One result states that under mild assumptions the number of equilibria will be finite (see regular economy) and odd (see index theorem). Furthermore, if an economy as a whole, as characterized by an aggregate excess demand function, has the revealed preference property (which is a much stronger condition than revealed preferences for a single individual) or the gross substitute property then likewise the equilibrium will be unique. All methods of establishing uniqueness can be thought of as establishing that each equilibrium has the same positive local index, in which case by the index theorem there can be but one such equilibrium.

Determinacy
Given that equilibria may not be unique, it is of some interest to ask whether any particular equilibrium is at least locally unique. If so, then comparative statics can be applied as long as the shocks to the system are not too large. As stated above, in a regular economy equilibria will be finite, hence locally unique. One reassuring result, due to Debreu, is that "most" economies are regular.

Work by Michael Mandler (1999) has challenged this claim. The Arrow–Debreu–McKenzie model is neutral between models of production functions as continuously differentiable and as formed from (linear combinations of) fixed coefficient processes. Mandler accepts that, under either model of production, the initial endowments will not be consistent with a continuum of equilibria, except for a set of Lebesgue measure zero. However, endowments change with time in the model and this evolution of endowments is determined by the decisions of agents (e.g., firms) in the model. Agents in the model have an interest in equilibria being indeterminate:

Indeterminacy, moreover, is not just a technical nuisance; it undermines the price-taking assumption of competitive models. Since arbitrary small manipulations of factor supplies can dramatically increase a factor's price, factor owners will not take prices to be parametric.

When technology is modeled by (linear combinations) of fixed coefficient processes, optimizing agents will drive endowments to be such that a continuum of equilibria exist:

The endowments where indeterminacy occurs systematically arise through time and therefore cannot be dismissed; the Arrow-Debreu-McKenzie model is thus fully subject to the dilemmas of factor price theory.

Some have questioned the practical applicability of the general equilibrium approach based on the possibility of non-uniqueness of equilibria.

Stability
In a typical general equilibrium model the prices that prevail "when the dust settles" are simply those that coordinate the demands of various consumers for various goods. But this raises the question of how these prices and allocations have been arrived at, and whether any (temporary) shock to the economy will cause it to converge back to the same outcome that prevailed before the shock. This is the question of stability of the equilibrium, and it can be readily seen that it is related to the question of uniqueness. If there are multiple equilibria, then some of them will be unstable. Then, if an equilibrium is unstable and there is a shock, the economy will wind up at a different set of allocations and prices once the convergence process terminates. However, stability depends not only on the number of equilibria but also on the type of the process that guides price changes (for a specific type of price adjustment process see Walrasian auction). Consequently, some researchers have focused on plausible adjustment processes that guarantee system stability, i.e., that guarantee convergence of prices and allocations to some equilibrium. When more than one stable equilibrium exists, where one ends up will depend on where one begins. The theorems that have been mostly conclusive when related to the stability of a typical general equilibrium model are closed related to that of the most local stability.

Unresolved problems in general equilibrium
Research building on the Arrow–Debreu–McKenzie model has revealed some problems with the model. The Sonnenschein–Mantel–Debreu results show that, essentially, any restrictions on the shape of excess demand functions are stringent. Some think this implies that the Arrow–Debreu model lacks empirical content. Therefore, an unsolved problem is

 * Is Arrow–Debreu–McKenzie equilibria stable and unique?

A model organized around the tâtonnement process has been said to be a model of a centrally planned economy, not a decentralized market economy. Some research has tried to develop general equilibrium models with other processes. In particular, some economists have developed models in which agents can trade at out-of-equilibrium prices and such trades can affect the equilibria to which the economy tends. Particularly noteworthy are the Hahn process, the Edgeworth process and the Fisher process.

The data determining Arrow-Debreu equilibria include initial endowments of capital goods. If production and trade occur out of equilibrium, these endowments will be changed further complicating the picture.

In a real economy, however, trading, as well as production and consumption, goes on out of equilibrium. It follows that, in the course of convergence to equilibrium (assuming that occurs), endowments change. In turn this changes the set of equilibria. Put more succinctly, the set of equilibria is path dependent... [This path dependence] makes the calculation of equilibria corresponding to the initial state of the system essentially irrelevant. What matters is the equilibrium that the economy will reach from given initial endowments, not the equilibrium that it would have been in, given initial endowments, had prices happened to be just right. – (Franklin Fisher).

The Arrow–Debreu model in which all trade occurs in futures contracts at time zero requires a very large number of markets to exist. It is equivalent under complete markets to a sequential equilibrium concept in which spot markets for goods and assets open at each date-state event (they are not equivalent under incomplete markets); market clearing then requires that the entire sequence of prices clears all markets at all times. A generalization of the sequential market arrangement is the temporary equilibrium structure, where market clearing at a point in time is conditional on expectations of future prices which need not be market clearing ones.

Although the Arrow–Debreu–McKenzie model is set out in terms of some arbitrary numéraire, the model does not encompass money. Frank Hahn, for example, has investigated whether general equilibrium models can be developed in which money enters in some essential way. One of the essential questions he introduces, often referred to as the Hahn's problem is: "Can one construct an equilibrium where money has value?" The goal is to find models in which existence of money can alter the equilibrium solutions, perhaps because the initial position of agents depends on monetary prices.

Some critics of general equilibrium modeling contend that much research in these models constitutes exercises in pure mathematics with no connection to actual economies. In a 1979 article, Nicholas Georgescu-Roegen complains: "There are endeavors that now pass for the most desirable kind of economic contributions although they are just plain mathematical exercises, not only without any economic substance but also without any mathematical value." He cites as an example a paper that assumes more traders in existence than there are points in the set of real numbers.

Although modern models in general equilibrium theory demonstrate that under certain circumstances prices will indeed converge to equilibria, critics hold that the assumptions necessary for these results are extremely strong. As well as stringent restrictions on excess demand functions, the necessary assumptions include perfect rationality of individuals; complete information about all prices both now and in the future; and the conditions necessary for perfect competition. However, some results from experimental economics suggest that even in circumstances where there are few, imperfectly informed agents, the resulting prices and allocations may wind up resembling those of a perfectly competitive market (although certainly not a stable general equilibrium in all markets).

Frank Hahn defends general equilibrium modeling on the grounds that it provides a negative function. General equilibrium models show what the economy would have to be like for an unregulated economy to be Pareto efficient.

Computing general equilibrium
Until the 1970s general equilibrium analysis remained theoretical. With advances in computing power and the development of input–output tables, it became possible to model national economies, or even the world economy, and attempts were made to solve for general equilibrium prices and quantities empirically.

Applied general equilibrium (AGE) models were pioneered by Herbert Scarf in 1967, and offered a method for solving the Arrow–Debreu General Equilibrium system in a numerical fashion. This was first implemented by John Shoven and John Whalley (students of Scarf at Yale) in 1972 and 1973, and were a popular method up through the 1970s. In the 1980s however, AGE models faded from popularity due to their inability to provide a precise solution and its high cost of computation.

Computable general equilibrium (CGE) models surpassed and replaced AGE models in the mid-1980s, as the CGE model was able to provide relatively quick and large computable models for a whole economy, and was the preferred method of governments and the World Bank. CGE models are heavily used today, and while 'AGE' and 'CGE' is used inter-changeably in the literature, Scarf-type AGE models have not been constructed since the mid-1980s, and the CGE literature at current is not based on Arrow-Debreu and General Equilibrium Theory as discussed in this article. CGE models, and what is today referred to as AGE models, are based on static, simultaneously solved, macro balancing equations (from the standard Keynesian macro model), giving a precise and explicitly computable result.

Other schools
General equilibrium theory is a central point of contention and influence between the neoclassical school and other schools of economic thought, and different schools have varied views on general equilibrium theory. Some, such as the Keynesian and Post-Keynesian schools, strongly reject general equilibrium theory as "misleading" and "useless". Other schools, such as new classical macroeconomics, developed from general equilibrium theory.

Keynesian and Post-Keynesian
Keynesian and Post-Keynesian economists, and their underconsumptionist predecessors criticize general equilibrium theory specifically, and as part of criticisms of neoclassical economics generally. Specifically, they argue that general equilibrium theory is neither accurate nor useful, that economies are not in equilibrium, that equilibrium may be slow and painful to achieve, and that modeling by equilibrium is "misleading", and that the resulting theory is not a useful guide, particularly for understanding of economic crises. "Let us beware of this dangerous theory of equilibrium which is supposed to be automatically established. A certain kind of equilibrium, it is true, is reestablished in the long run, but it is after a frightful amount of suffering."

- Simonde de Sismondi, New Principles of Political Economy, vol. 1, 1819, pp. 20-21.

"The long run is a misleading guide to current affairs. In the long run we are all dead. Economists set themselves too easy, too useless a task if in tempestuous seasons they can only tell us that when the storm is past the ocean is flat again."

- John Maynard Keynes, A Tract on Monetary Reform, 1923, ch. 3

"It is as absurd to assume that, for any long period of time, the variables in the economic organization, or any part of them, will "stay put," in perfect equilibrium, as to assume that the Atlantic Ocean can ever be without a wave."

- Irving Fisher, The Debt-Deflation Theory of Great Depressions, 1933, p. 339

Robert Clower and others have argued for a reformulation of theory toward disequilibrium analysis to incorporate how monetary exchange fundamentally alters the representation of an economy as though a barter system. • Robert W. Clower (1965). "The Keynesian Counter-Revolution: A Theoretical Appraisal," in F.H. Hahn and F.P.R. Brechling, ed., The Theory of Interest Rates. Macmillan. Reprinted in Clower (1987), Money and Markets. Cambridge. Description and preview via scroll down. pp. 34-58. • _____ (1967). "A Reconsideration of the Microfoundations of Monetary Theory," Western Economic Journal, 6(1), pp. 1–8 (press +). • _____ and Peter W. Howitt (1996). "Taking Markets Seriously: Groundwork for a Post-Walrasian Macroeconomics", in David Colander, ed., Beyond Microfoundations, pp. 21–37. • Herschel I. Grossman (1971). "Money, Interest, and Prices in Market Disequilibrium," Journal of Political Economy,79(5), p p. 943–961. • Jean-Pascal Bénassy (1990). "Non-Walrasian Equilibria, Money, and Macroeconomics," Handbook of Monetary Economics, v. 1, ch. 4, pp. 103-169. Table of contents. • _____ (1993). "Nonclearing Markets: Microeconomic Concepts and Macroeconomic Applications," Journal of Economic Literature, 31(2), pp. 732–761 (press +). • _____ (2008). "non-clearing markets in general equilibrium," in The New Palgrave Dictionary of Economics, 2nd Edition. Abstract.

New classical macroeconomics
While general equilibrium theory and neoclassical economics generally were originally microeconomic theories, new classical macroeconomics builds a macroeconomic theory on these bases. In new classical models, the macroeconomy is assumed to be at its unique equilibrium, with full employment and potential output, and that this equilibrium is assumed to always have been achieved via price and wage adjustment (market clearing). The best-known such model is real business-cycle theory, in which business cycles are considered to be largely due to changes in the real economy, unemployment is not due to the failure of the market to achieve potential output, but due to equilibrium potential output having fallen and equilibrium unemployment having risen.

Socialist economics
Within socialist economics, a sustained critique of general equilibrium theory (and neoclassical economics generally) is given in Anti-Equilibrium, based on the experiences of János Kornai with the failures of Communist central planning, although Michael Albert and Robin Hahnel later based their Parecon model on the same theory.

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title: General equilibrium theory