The Pythia (pronounced // or //, Greek: Πυθία [pyːˈtʰi.a]), commonly known as the Oracle of Delphi, was the priestess at the Temple of Apollo at Delphi, located on the slopes of Mount Parnassus, beneath the Castalian Spring. The Pythia was widely credited for her prophecies inspired by Apollo. The Delphic oracle was established in the 8th century BC, although it may have been present in some form in Late Mycenaean times, from 1,400 BC and was abandoned, and there is evidence that Apollo took over the shrine from an earlier dedication to Gaia. The last recorded response was given during 393 A.D., when the emperor Theodosius I ordered pagan temples to cease operation.
During this period the Delphic Oracle was the most prestigious and authoritative oracle among the Greeks. The oracle is one of the best-documented religious institutions of the classical Greeks. Authors who mention the oracle include Aeschylus, Aristotle, Clement of Alexandria, Diodorus, Diogenes, Euripides, Herodotus, Julian, Justin, Livy, Lucan, Ovid, Pausanias, Pindar, Plato, Plutarch, Sophocles, Strabo, Thucydides, and Xenophon.
The name 'Pythia' derived from Pytho, which in myth was the original name of Delphi. The Greeks derived this place name from the verb, pythein (πύθειν, "to rot"), which refers to the decomposition of the body of the monstrous Python after she was slain by Apollo. The usual theory has been that the Pythia delivered oracles in a frenzied state induced by vapors rising from a chasm in the rock, and that she spoke gibberish which priests interpreted as the enigmatic prophecies preserved in Greek literature.
Recent geological investigations have shown that gas emissions from a geologic chasm in the earth could have inspired the Delphic Oracle to "connect with the divine." Some researchers suggest the possibility that ethylene gas caused the Pythia's state of inspiration. However, Lehoux argues that ethylene is "impossible" and benzene is "crucially underdetermined." Others argue instead that methane might have been the gas emitted from the chasm, or CO2 and H2S, arguing that the chasm itself might have been a seismic ground rupture, although this idea has been challenged by scholars such as Joseph Fontenrose and Lisa Maurizio, who argue that the ancient sources uniformly represent the Pythia speaking intelligibly, and giving prophecies in her own voice.
Origins of the Oracle 
The earliest account of the origin of the Delphic oracle is provided in the Homeric Hymn to Delphic Apollo, which recent scholarship dates within a narrow range, ca. 580-570 BC. It describes in detail how Apollo chose his first priests, whom he selected in their "swift ship"; they were "Cretans from Minos' city of Knossos" who were voyaging to sandy Pylos. But Apollo, who had Delphinios as one of his cult epithets, leapt into the ship in the form of a dolphin (delphinos). Dolphin-Apollo revealed himself to the terrified Cretans, and bade them follow him up to the "place where you will have rich offerings". The Cretans "danced in time and followed, singing Iē Paiēon, like the paeans of the Cretans in whose breasts the divine Muse has placed "honey-voiced singing". "Paean" seems to have been the name by which Apollo was known in Mycenaean times.
G.L. Huxley observes, "If the hymn to (Delphic) Apollo conveys a historical message, it is above all that there were once Cretan priests at Delphi." Robin Lane Fox notes that Cretan bronzes are found at Delphi from the eighth century onwards, and Cretan sculptures are dedicated as late as ca 620-600 BC: ""Dedications at the site cannot establish the identity of its priesthood," he observes, "but for once we have an explicit text to set beside the archaeological evidence." An early visitor to these "dells of Parnassus", at the end of the eighth century, was Hesiod, who was shown the omphalos.
There are also many later stories of the origins of the Delphic Oracle. One late explanation, which is first related by the 1st century BC writer, Diodorus Siculus, tells of a goat herder named Coretas, who noticed one day that one of his goats, who fell into a crack in the earth, was behaving strangely. On entering the chasm, he found himself filled with a divine presence and could see outside of the present into the past and the future. Excited by his discovery he shared it with nearby villagers. Many started visiting the site to experience the convulsions and inspirational trances, though some were said to disappear into the cleft due to their frenzied state. A shrine was erected at the site, where people began worshiping in the late Bronze Age, by 1600 BC. The villagers chose a single young woman as the liaison for the divine inspirations. Eventually she spoke on behalf of gods.
According to earlier myths, the office of the oracle was initially possessed by the goddesses Themis and Phoebe, and the site was initially sacred to Gaia. Subsequently it was believed to be sacred to Poseidon, the "Earth-shaker" god of earthquakes. During the Greek Dark Age, from the 11th to the 9th century BC, a new god of prophecy, Apollo, allegedly seized the temple and expelled the twin guardian serpents of Gaia. Later myths stated that Phoebe or Themis had "given" the site to Apollo, rationalizing its seizure by priests of the new god, but presumably, having to retain the priestesses of the original oracle because of the long tradition. Apparently Poseidon was mollified by the gift of a new site in Troizen.
Diodorus also explained how, initially, the Pythia was an appropriately clad young virgin, for great emphasis was placed on the Oracle's chastity and purity to be reserved for union with the god Apollo. But one consultant notes,
|“||Echecrates the Thessalian, having arrived at the shrine and beheld the virgin who uttered the oracle, became enamoured of her because of her beauty, carried her away and violated her; and that the Delphians because of this deplorable occurrence passed a law that in the future a virgin should no longer prophesy but that an elderly woman of fifty would declare the Oracles and that she would be dressed in the costume of a virgin, as a sort of reminder of the prophetess of olden times.||”|
The scholar Martin Litchfield West writes that the Pythia shows many traits of shamanistic practices, likely inherited or influenced from Central Asian practices, although there is no evidence of any Central Asian association at this time. He cites the Pythia sitting in a cauldron on a tripod, while making her prophecies in an ecstatic trance state, like shamans, and her unintelligible utterings.
Organization of the Oracle 
Though little is known of how the priestess was chosen, the Pythia was probably selected, at the death of her predecessor, from amongst a guild of priestesses of the temple. These women were all natives of Delphi and were required to have had a sober life and be of good character. Although some were married, upon assuming their role as the Pythia, the priestesses ceased all family responsibilities, marital relations, and individual identity. In the heyday of the oracle, the Pythia may have been a woman chosen from an influential family, well educated in geography, politics, history, philosophy, and the arts. During later periods, however, uneducated peasant women were chosen for the role, which may explain why the poetic pentameter or hexameter prophecies of the early period, later were made only in prose. The archaeologist John Hale reports:
|“||the Pythia was (on occasion) a noble of aristocratic family, sometimes a peasant, sometimes rich, sometimes poor, sometimes old, sometimes young, sometimes a very lettered and educated woman to whom somebody like the high priest and the philosopher Plutarch would dedicate essays, other times who could not write her own name. So it seems to have been aptitude rather than any ascribed status that made these women eligible to be Pythias and speak for the god.||”|
The job of a priestess, especially the Pythia, was a respectable career for Greek women. Priestesses enjoyed many liberties and rewards for their societal position, such as freedom from taxation, the right to own property and attend public events, a salary and housing provided by the state, a wide range of duties depending on their affiliation, and often gold crowns.
During the main period of the oracle's popularity, as many as three women served as Pythia, another vestige of the triad, with two taking turns in giving prophecy and another kept in reserve.
Plutarch said that the Pythia's life was shortened through the service of Apollo. The sessions were said to be exhausting. At the end of each period the Pythia would be like a runner after a race or a dancer after an ecstatic dance, which may have had a physical effect on the health of the Pythia.
Several other officials served the oracle in addition to the Pythia. After 200 BC at any given time there were two priests of Apollo, who were in charge of the entire sanctuary; Plutarch, who served as a priest during the late first century and early second century CE, gives us the most information about the organization of the oracle at that time. Before 200 BC, while the temple was dedicated to Apollo, there was probably only one priest of Apollo. Priests were chosen from among the main citizens of Delphi, and were appointed for life. In addition to overseeing the oracle, priests would also conduct sacrifices at other festivals of Apollo, and had charge of the Pythian games. Earlier arrangements, before the temple became dedicated to Apollo, are not documented.
The other officials associated with the oracle are less well known. These are the hosioi ("holy ones") and the prophētai (singular prophētēs). Prophētēs is the origin of the English word "prophet", but a better translation of the Greek word might be "one who speaks on behalf of another person." The prophetai are referred to in literary sources, but their function is unclear; it has been suggested that they interpreted the Pythia's prophecies, or even reformatted her utterances into verse, but it has also been argued that the term prophētēs is a generic reference to any cult officials of the sanctuary, including the Pythia. There were five hosioi, whose responsibilities are unknown, but may have been involved in some manner with the operation of the oracle.
Oracular procedure 
In the traditions associated with Apollo, the oracle only gave prophecies during the nine warmest days of each year. During winter months, Apollo was said to have deserted his temple, his place being taken by his divine half-brother Dionysus, whose tomb was within the temple. It is not known whether the Oracle participated with the Dionysian rites of the Maenads or Thyades in the Korykion cave on Mount Parnassos, although Plutarch informs us that his friend Clea was both a Priestess to Apollo and to the secret rites of Dionysus. The male priests seem to have had their own ceremonies to the dying and resurrecting God. Apollo was said to return at the beginning of Spring, on the 7th day of the month of Vysios, his birthday. This also would reiterate the absences of the great goddess Demeter in winter also, which would have been a part of the earliest traditions.
Once a month, thereafter, the oracle would undergo purification rites, including fasting, to ceremonially prepare the Pythia for communications with the divine. On the seventh day of each month, she would bathe in the Castalian Spring then would drink the holier waters of the Kassotis, which flowed closer to the temple, where a naiad possessing magical powers was said to live. Euripides described this ritual purification ceremony, starting first with the priest Ion dancing on the highest point of Mount Parnassus, going about his duties within the temple, and sprinkling the temple floor with holy water. The purification ceremonies always were performed on the seventh day of the month, which was sacred to and associated with the god Apollo.
Carved into the entrance of the temple were two phrases, which seem to have played an important part in the later temple ritual: γνῶθι σεαυτόν (gnōthi seautón = "know thyself") and μηδέν άγαν (mēdén ágan = "nothing in excess"), and an enigmatic "E". According to Plutarch's essay on the meaning of the "E at Delphi"—the only literary source for the inscription, there have been various interpretations of this letter. It has been interpreted as the first letter of Ἑγγύα πάρα δ'ἄτη (eggýa pára d'atē) = "make a pledge and mischief is nigh", In ancient times, the origin of these phrases was attributed to one or more of the Seven Sages of Greece.
The Oracle then descended into the adyton (Greek for "inaccessible") and mounted her tripod seat, holding laurel leaves and a dish of Kassotis spring water into which she gazed. Nearby was the omphalos (Greek for "navel"), which was flanked by two solid gold eagles representing the authority of Zeus, and the cleft from which emerged the sacred pneuma.
Consultants, carrying laurel branches sacred to Apollo, approached the temple along the winding upward course of the Sacred Way, bringing an animal for sacrifice in the forecourt of the temple, and a monetary fee. Petitioners drew lots to determine the order of admission, but representatives of a city-state or those who brought larger donations to Apollo were secured a higher place in line. The sacrificial animal, often a goat as representation of the site's discovery, was first showered with water and observed to ensure that it shivered from the hooves upward, an auspicious sign that the oracular reading could proceed. Upon sacrifice, the animal's organs, particularly its liver, were examined to ensure the signs were favorable.
Plutarch describes the events of one session in which the omens were ill-favored, but the Oracle was consulted nonetheless. The priests proceeded to receive the prophecy, but the result was a hysterical uncontrollable reaction from the priestess that resulted in her death a few days later.
At times when the Pythia was not available, consultants could obtain guidance by asking simple Yes-or-No questions to the priests. A response was returned through the tossing of colored beans, one color designating "yes," another "no." Little else is known of this practice.
Between 535 and 615 of the Oracles of Delphi are known to have survived since classical times, of which over half are said to be accurate historically (see the article Famous Oracular Statements from Delphi for some examples).
The experience of supplicants 
In antiquity, the people who went to the Oracle to ask for advice were known as “consultants,” literally, “those who seek counsel.” . It would appear that the supplicant to the oracle would undergo a four-stage process, typical of shamanic journeys.
- Step 1: Journey to Delphi — Supplicants were motivated by some need to undertake the long and sometimes arduous journey to come to Delphi in order to consult the oracle. This journey was motivated by an awareness of the existence of the oracle, the growing motivation on the part of the individual or group to undertake the journey, and the gathering of information about the oracle as providing answers to important questions.
- Step 2: Preparation of the Supplicant — Supplicants were interviewed in preparation of their presentation to the Oracle, by the priests in attendance. The genuine cases were sorted and the supplicant had to go through rituals involving the framing of their questions, the presentation of gifts to the Oracle and a procession along the Sacred Way carrying laurel leaves to visit the temple, symbolic of the journey they had made.
- Step 3: Visit to the Oracle — The supplicant would then be led into the temple to visit the adyton, put his question to the Pythia, receive his answer and depart. The degree of preparation already undergone would mean that the supplicant was already in a very aroused and meditative state, similar to the shamanic journey elaborated on in the article.
- Step 4: Return Home — Oracles were meant to give advice to shape future action, that was meant to be implemented by the supplicant, or by those that had sponsored the supplicant to visit the Oracle. The validity of the Oracular utterance was confirmed by the consequences of the application of the oracle to the lives of those people who sought Oracular guidance.
Scientific explanations 
Fumes and vapors 
There have been many attempts to find a scientific explanation for the Pythia's inspiration. However, most commonly, these refer to an observation made by Plutarch, who presided as high priest at Delphi for several years, who stated that her oracular powers appeared to be associated with vapors from the Kerna spring waters that flowed under the temple. It has often been suggested that these vapors may have been hallucinogenic gases.
Beginning during 1892, a team of French archaeologists directed by Théophile Homolle of the Collège de France excavated the site at Delphi. Contrary to ancient literature, they found no fissure and no possible means for the production of fumes.
Adolphe Paul Oppé published an influential article in 1904, which made three crucial claims: No chasm or vapor ever existed; no natural gas could create prophetic visions; and the recorded incidents of a priestess undergoing violent and often deadly reactions was inconsistent with the more customary reports. Oppé explained away all the ancient testimony as being reports of gullible travelers fooled by wily local guides who, Oppé believed, invented the details of a chasm and a vapor in the first place.
In accordance with this definitive statement, such scholars as Frederick Poulson, E.R. Dodds, Joseph Fontenrose, and Saul Levin all stated that there were no vapors and no chasm. For the decades to follow, scientists and scholars believed the ancient descriptions of a sacred, inspiring pneuma to be fallacious. During 1950, the French hellenist Pierre Amandry, who had worked at Delphi and later directed the French excavations there, concurred with Oppé's pronouncements, claiming that gaseous emissions were not even possible in a volcanic zone such as Delphi. Neither Oppé nor Amandry were geologists, though, and no geologists had been involved in the debate up to that point.
Subsequent re-examination of the French excavations, however, has shown that this consensus may have been mistaken. Broad (2007) demonstrates that a French photograph of the excavated interior of the temple clearly depicts a springlike pool as well as a number of small vertical fissures, indicating numerous pathways by which vapors could enter the base of the temple.
During the 1980s, the interdisciplinary team of geologist Jelle Zeilinga de Boer, archaeologist John R. Hale, forensic chemist Jeffrey P. Chanton, and toxicologist Henry R. Spiller investigated the site at Delphi using this photograph and other sources as evidence, as part of a United Nations survey of all active faults in Greece.
Jelle Zeilinga de Boer saw evidence of a fault line in Delphi that lay under the ruined temple. During several expeditions, they discovered two major fault lines, one lying north-south, the Kerna fault, and the other lying east-west, the Delphic fault, which parallels the shore of the Corinthian Gulf. The rift of the Gulf of Corinth is one of the most geologically active sites on Earth; shifts there impose immense strains on nearby fault lines, such as those below Delphi. The two faults cross one another, and they intersect right below where the adyton was probably located. (The actual, original oracle chamber had been destroyed by the moving faults, but there is strong structural evidence that indicates where it was most likely located.)
They also found evidence for underground passages and chambers, and drains for spring water. Additionally, they discovered at the site formations of travertine, a form of calcite created when water flows through limestone and dissolves calcium carbonate, which is later redeposited. Further investigation revealed that deep beneath the Delphi region lies bituminous deposit, rich in hydrocarbons and full of pitch, that has a petrochemical content as high as 20%. Friction created by earthquakes heat the bituminous layers resulting in vaporization of the hydrocarbons which rise to the surface through small fissures in the rock.
Illusions in the adyton 
It has been disputed as to how the adyton was organized, but it appears clear that this temple was unlike any other in Ancient Greece. The small chamber was located below the general floor of the temple and offset to one side, perhaps constructed specifically over the crossing faults. The intimate chamber allowed the escaping vapors to be contained in quarters close enough to provoke intoxicating effects. Plutarch reports that the temple was filled with a sweet smell when the "deity" was present:
|“||Not often nor regularly, but occasionally and fortuitously, the room in which they seat the god's consultants is filled with a fragrance and breeze, as if the adyton were sending forth the essences of the sweetest and most expensive perfumes from a spring (Plutarch Moralia 437c).||”|
De Boer's research caused him to speculate ethylene as a gas known to possess this sweet odor. Toxicologist Henry R. Spiller specified that inhalation of even a small amount of ethylene can cause both benign trances and euphoric frenzied states. Other effects include physical detachment, loss of inhibitions, the relieving of pain, and rapidly changing moods without dulling consciousness. He also noted that uncontrolled doses can cause confusion, agitation, delirium, and loss of muscle coordination.
Anesthesiologist Isabella Herb found that a dose of 20% ethylene gas administered to a subject was a threshold. A dosage higher than 20% caused unconsciousness. With less than 20% a trance was induced where the subject could sit up, hear questions and answer them logically, although the tone of their voice might be altered, their speech pattern could be changed, and they may have lost some awareness of their hands and feet, (with some it was possible to have poked a pin or pricked them with a knife and they would not feel it). When patients were removed from the area where the gas accumulated they had no recollection of what had happened, or what they had said. With a dosage of more than 20% the patient lost control over the movement of their limbs and may thrash wildly, groaning in strange voices, losing balance and frequently repeatedly falling. All of these symptoms match the experience of the Pythia in action, as related by Plutarch, who witnessed many prophecies.
During 2001, water samples from the nearby springs yielded evidence of the presence of the hallucinogenic hydrocarbon. The Kerna spring, originating uphill from the temple, yielded 0.3 parts per million of ethylene. Presently, the waters of the Kerma spring are diverted from the temple for use by the nearby modern town of Delphi. It is unknown the degree to which ethylene or other gases would be detected at the temple should these waters still flow freely, as they did in the ancient world.
Chunks of travertine, calcareous rock formed of mineral spring deposits, were also extracted from the temple and tested, but no traces of ethylene were identified. The nature of the hydrocarbon accounts for this. Ethylene is extremely light and volatile, having a highly reactive nature, and therefore could have presumably escaped the rock long ago. By testing the samples from the spring water, the team was at least able to identify the substance's current presence at the site, giving them insight that a presumably larger quantity existed in the waters thousands of years earlier.
Frequent earthquakes produced by the fact that Greece lies at the intersection of three separate tectonic plates seem to have been responsible for the observed cracking of the limestone, and the opening up of new channels by which hydrocarbons enter the flowing waters of the Kassotis. This would cause the amounts of ethylene emitted to fluctuate, increasing or decreasing the potency of the drug released, over time. It has been suggested that the decrease of importance of the Oracle after the era of Roman Emperor Hadrian was due in part to the fact that there had not been an earthquake in the area for a significant time.
Another interpretation, by art historian Merlin Stone, suggests the use of venom rather than ethylene. She indicates that when people, after having been immunized against snake-bite, are bitten by a venomous snake, particularly by krait, cobra or another elapids, they experience an emotional and mental state that has been compared to the effects of hallucinogenic substances.
See also 
- List of oracular statements from Delphi
- Theia mania, a concept used to describe the Pythia's divine inspiration in Plato's Phaedrus.
- The Apollonian and Dionysian, concept of human dichotomy.
- Delphi method, a structured communication technique, unrelated to the Oracle of Delphi.
- Morgan 1990, p. 148.
- see discussion in Deitrich, Bernard C. (1992), "Divine Madness and Conflict at Delphi" (Kernos 5) PDF at http://scholar.google.com/scholar?hl=en&q=Mycenaean+Delphi&btnG=&as_sdt=1%2C5&as_sdtp=
- Fortenrose. J. (1959) "Python. A Study ofDelphic Myth and Its Origins, (Berkeley)
- Homeric Hymn to Apollo 363-369.
- For an example, see Lewis Farnell, The Cults of the Greek States, 1907, vol. IV, p.189. "But all this came to be merely considered as an accessory, leading up to the great moment when the Pythoness ascended into the tripod, and, filled with the divine afflatus which at least the latter ages believed to ascend in vapour from a fissure in the ground, burst forth into wild utterance, which was probably some kind of articulate speech, and which the Ὅσιοι [Osioi], 'the holy ones', who, with the prophet, sat around the tripod, knew well how to interpret. ... What was essential to Delphic divination, then, was the frenzy of the Pythoness and the sounds which she uttered in this state which were interpreted by the Ὅσιοι [Osioi] and the 'prophet' according to some conventional code of their own."
- Lehoux, 2007
- Piccardi, 2000; Spiller et al., 2000; de Boer, et al., 2001; Hale et al. 2003; Etiope et al., 2006; Piccardi et al., 2008.
- Mason, Betsy. The Prophet of Gases in ScienceNow Daily News 2 October 2006. Retrieved 11 October 2006.
- Fontenrose 1978, pp. 196-227; Maurizio 2001, pp. 38-54.
- Forrest, W.G. (1957), "Colonisation and the Rise of Delphi" (Historia: Zeitschrift für Alte Geschichte Bd. 6, H. 2 (Apr., 1957), pp. 160-175)
- Martin L. West, Homeric Hymns, pp 9-12, gives a summary for this dating, at or soon after the inauguration of chariot-racing at the Pythian Games, 582 BC; M. Chappell, "Delphi and the Homeric Hymn to Apollo", Classical Quarterly 56 (2006:331-48)
- As Robin Lane Fox observes in discussing this origin of the Delphic priesthood, in Travelling Heroes in the Epic Age of Homer, 2008:341ff.
- Huxley, "Cretan Paiawones". Greek, Roman and Byzantine Studies 16 (1975:119-24) p. 122, noted by Fox 2008:343.
- Fox 2008:342.
- Diodorus Siculus 16.26.1-4.
- Broad, W. J. (2007), p.21. It was also said that the young woman was given a tripod on which to be seated, which acted on behalf of her own safety during her frenzied states.
- Smith's Dictionary of Greek and Roman Biography and Mythology notes on this point Ovid, Metamorphoses i. 321, iv. 642; Apollonius Rhodius, Argonautica iv. 800; Servius, commentary on the Aeneid iv. 246; pseudo-Apollodorus, Bibliotheke i. 4. § 1 ; Pausanias x. 5. § 3; Aeschylus, The Eumenides opening lines; see excerpts in translation at Theoi Project: Themis.
- D. S. Robertson, "The Delphian Succession in the Opening of the Eumenides" The Classical Review 55. 2 (September 1941, pp. 69-70) p. 69, reasoning that in the three great allotments of oracular powers at Delphi, corresponding to the three generations of the gods, "Ouranos, as was fitting, gave the oracle to his wife Gaia and Kronos appropriately allotted it to his sister Themis." In Zeus' turn to make the gift, however, Aeschylus could not report that the oracle was given directly to Apollo, who had not yet been born, Robertson notes, and thus Phoebe was interposed. However, the usual modern reconstruction of the sacred site's pre-Olympian history does not indicate dedications to these earlier gods.
- Broad, W. J. (2007), p.30-31
- Martin Litchfield West, The Orphic Poems, p.147. "The Pythia resembles a shamaness at least to the extent that she communicates with her [deity] while in a state of trance, and conveys as much to those present by uttering unintelligible words. [cf. Spirit Language, Mircea Eliade]. It is particularly striking that she sits on a cauldron supported by a tripod, reiterating the triad of the great goddess. This eccentric perch can hardly be explained except as a symbolic boiling, and, as such, it looks very much like a reminiscence of the initiatory boiling of the shaman translated from hallucinatory experience into concrete visual terms. It was in this same cauldron, probably, that the Titans boiled Dionysus in the version of the story known to Callimachus and Euphorion, and his remains were interred close by".
- Broad, W. J. (2007), p.31-32
- Herbert W Parke, History of the Delphic Oracle and H.W. Parke and D.E.W. Wormell The Delphic oracle, 1956 Volume 1: The history attempt the complicated reconstruction of the oracle's institutions; a recent comparison of the process of select at Delphi with Near Eastern oracles is part of Herbert B. Huffman, "The Oracular Process: Delphi and the Near East" Vetus Testamentum 57.4, (2007:449-60).
- quoted in an interview on the radio program "The Ark", transcript available.
- Broad, W. J. (2007), p.32
- Plutarch Moralia 414b.
- "Plutarch • On the Failure of Oracles". Penelope.uchicago.edu. Retrieved 2012-03-19.
- On the temple personnel, see Roux 1976, pp. 54-63.
- Bowden 2005, pp. 15-16; see also Herodotus 8.36, Euripides Ion 413-416.
- Plutarch, op cit
- Broad, W. J. (2007), p.34-36.
- Hodge, A. Trevor. "The Mystery of Apollo's E at Delphi," American Journal of Archaeology, Vol. 85, No. 1. (Jan., 1981), pp. 83–84.
- Plato, Charmides 164d–165a.
- Plato, Protagoras 343a–b.
- Broad, W. J. (2007), p.38-40
- Fontenrose, op cit
- http://www.wisecounselresearch.com/research/portrait-gallery/delphic-oracle sighted 14/5/2013
- Fontenrose, Joseph (1981), "Delphic Oracle: Its Responses and Operations". (Uni of Calif. Press)
- J.Z. De Boer, and J. R. Hale. “The Geological Origins of the Oracle of Delphi, Greece,” in W.G. McGuire, D.R. Griffiths, P Hancock, and I.S. Stewart, eds. The Archaeology of Geological Catastrophes. (Geological Society of London) 2000. Popular accounts in A&E Television Networks. History Channel documentary Oracle at Delphi, Secrets Revealed, 2003, and in William J. Broad, The Oracle: The Lost Secrets and Hidden Message of Ancient Delphi. (New York: Penguin) 2006.
- Delphi, the OIracle of Apollo from Adventures in Archaeology
- The Oracle at Delphi Medb hErren
- Broad W.J. (2007), pp. 146-7: "[A] French photo of the temple's interior showed not only a spring-like pool but fissures... in the bedrock, suggesting a specific pathway by which intoxicating gases could have risen into the oracle's sanctum... What delighted de Boer so much was not the verification of the spring-like pool at the heart of the chasm, as the revelation of the bedrock's composition... there right above the waterline, the photograph clearly showed vertical fissures running through the bedrock. No denial could hide that fact, no scholarly disclaimer could deny the reality.... [The] cracks ...[showed] evidence of tectonic jolts and protracted flows of mineralized water."
- Jelle Zeilinga de Boer - Retrieved on 2006-10-01.
- John R. Hale - Retrieved on 2006-10-01.
- Jeffrey P. Chanton - Retrieved on 2006-10-01.
- Henry R. Spiller - Retrieved on 2006-10-01.
- Broad (2007), p. 155-7
- In the French excavation report on the temple, Fernand Courby shows that the adyton was unlike those found in other temples as it was not central, but on the southwestern side, interrupting the normal symmetry of the Doric temple. It was divided into two areas, one small area 9 by 16 feet for the oracle, one for the supplicant. Modern research reported by Broad (p. 37) suggests that both the supplicant and the Pythia descended a flight of five steps into a small room within the temple with its own low ceiling. Walter Miller has argued that the stone block of 3.5-4 feet, that Courby described as being part of the floor, was in fact the site where the oracle sat. It showed a square 6 inch hole, that widened to 9 inches, immediately under the triangular grooves for the tripod. Strange channels, possibly to carry water from the spring, surrounded the tripodal grooves. That these had in fact carried waters for long periods was confirmed by the layers of travertine that encrusted it. Nothing like this has been found at any other Greek temple. Holland (1933) argues that these channels and the hollow nature of the omphalos found by the French would channel the vapors of intoxicant gases.
- Broad (2007), p. 172
- Broad (2007), p.212-4
- Interview with John R. Hale on the Delphic Oracle, ABC News, Australia - (Retrieved on 2006-04-20)
- Broad (2007), p. 198. Methane (15.3 parts per million) and ethane (0.2 ppm) were also detected in the Kerna sample. However, the intoxicating effects of ethylene are more powerful than those of methane or ethane.
- "the Kerna Spring, once alive but now vanished since Greek engineers had re-routed its waters to supply the town of Delphi" Tests from a number of nearby sites showed the concentration of Ethylene at Kerna was ten times that of other nearby springs. In an interview reported in Broad (2006, p. 152), de Boer stated that "the Kerna sample, because of the spring's rerouting, had to be drawn from a city's holding tank ... letting some of the gas escape as it sat... and lessened the water concentrations. If so the actual levels of the methane, ethane and ethylene that came out of the ground would have been higher".
- Broad (2007), p. 194-5
- Stone, Merlin When God was a Woman, Mariner Books, 1978
Ancient sources 
- Herodotus, The Histories, at the Perseus Project
- Homeric Hymn to Apollo, at the Perseus Project
- Pausanias, Description of Greece, (ed. and translated with commentary by Sir James Frazer), 1913 edition. Cf. v.5
- Plutarch, De defectu oraculorum ("On the Decline of Oracles") and De Pythiae Oraculis ("On the Oracles of the Pythia"), in Moralia, vol. 5 (Loeb Library, Harvard University Press)
Modern sources 
- de Boer, Jelle Zeilinga, John Rigby Hale & Henry A. Spiller, "The Delphic Oracle: A Multidisciplinary Defense of the Gaseous Vent Theory." Clinical Toxicology 40.2 189-196 (2000)
- de Boer, Jelle Zeilinga, Jeffrey P. Chandon & John Rigby Hale, "New Evidence for the Geological Origins of the Ancient Delphic Oracle," Geology 29.8, 707-711 (2001)
- de Boer, Jelle Zeilinga, Jeffrey P. Chandon, John Rigby Hale & Henry A. Spiller, "Questioning the Delphic Oracle", Scientific American (August 2003)
- Bouché-Leclercq, Auguste, Histoire de la divination dans l'Antiquité, volumes I-IV, Paris (1879–1882)
- Bowden, Hugh (2005). Classical Athens and the Delphic Oracle: Divination and Democracy. Cambridge University Press. ISBN 0-521-53081-4.
- Broad, William J. The Oracle: Ancient Delphi and the Science Behind Its Lost Secrets, New York, Penguin Press, ISBN 978-0-14-303859-7 (2007); hardcover edition The Oracle: the lost secrets and hidden message of ancient Delphi, Penguin Press, ISBN 1-59420-081-5 (2006)
- Burkert, Walter Greek Religion, Harvard University Press, ISBN 0-674-36280-2 (1985); Orig. in German (1977)
- Connelly, Joan Breton Portrait of a Priestess: Women and Ritual in Ancient Greece, Princeton University Press, 2007, ISBN 0-691-12746-8
- Courby, Fernand, Feuilles de Delphi: Tome 2, Topographie et Architecture, La Terrace du Temple (1927)
- Dempsey, T., Reverend, The Delphic oracle, its early history, influence and fall, Oxford, B.H. Blackwell (1918)
- Dodds, E. R. The Greeks and the Irrational, Berkeley, University of California Press (1963)
- Etiope, G., D. Christodoulou, M. Geraga, P. Favali, & G. Papatheodorou, "The geological links of the ancient Delphic Oracle (Greece): a reappraisal of natural gas occurrence and origin", Geology, 34, 821-824 (2006)
- Farnell, Lewis Richard, The Cults of the Greek States, Volumes I-V, Clarendon Press, (1896–1909); cf. especially, volume IV on the Pythoness and Delphi
- Fontenrose, Joseph Eddy, Python; a study of Delphic myth and its origins, New York, Biblio & Tannen, ISBN 0-8196-0285-X (1959; 1974)
- Fontenrose, Joseph Eddy, The Delphic oracle, its responses and operations, with a catalogue of responses, Berkeley : University of California Press, ISBN 0-520-03360-4 (1978)
- Foster J., Lehoux D.R., "The Delphic Oracle and the ethylene-intoxication hypothesis", Clinical Toxicology, 45, 85-89 (2007)
- Golding, William, The Double Tongue, London, Faber (1995). Posthumous, fictional novel by the Nobel prize winner about a Pythia in the 1st century BCE.
- Goodrich, Norma Lorre, Priestesses, New York : F. Watts, ISBN 0-531-15113-1 (1989); Harper Collins, Perennial, ISBN 0-06-097316-1 (1990)
- Guthrie, William Keith Chambers, The Greeks and their Gods (1950)
- Hall, Manly Palmer, The Secret Teachings of All Ages, Cf Chapter 14, (1928)
- Holland, Leicester B., "The Mantic Mechanism at Delphi," American Journal of Archaeology 37 pp. 201–214 (1933)
- Lehoux D.R., "Drugs and the Delphic Oracle", Classical World, 101, 1, 41-56 (2007)
- Maass, E., De Sibyllarum Indicibus, Berlin (1879)
- Maurizio, Lisa, "The Voice at the Centre of the World: The Pythia's Ambiguity and Authority" pp. 46–50 in editors Andre Lardinois and Laura McClure Making Silence Speak: Women's Voices in Greek Literature and Society, Princeton University Press (2001)
- Miller, Water, Daedalus and Thespis Vol 1, (1929)
- Mitford, William, The History of Greece (1784); Cf. v.1, Chapter III, Section 2, p. 177, "Origin and Progress of the Oracles"
- Morgan, Catherine. Athletes and Oracles, Cambridge (1990)
- Parke, Herbert William, A History of the Delphic Oracle, Basil Blackwell, Oxford, ASIN B002NZWT0Y (1939)
- Parke, Herbert William, Sibyls and Sibylline Prophecy in Classical Antiquity, Routledge, London, ISBN 978-0-415-07638-8 (reprinted 1992)
- Piccardi, Luigi, "Active faulting at Delphi: seismotectonic remarks and a hypothesis for the geological environment of a myth", Geology, 28, 651-654 (2000)
- Piccardi L., C. Monti, F. Tassi O. Vaselli, D. Papanastassiou & K. Gaki-Papanastassiou, "Scent of a myth: tectonics, geochemistry and geomythology at Delphi (Greece)", Journal of the Geological Society, London, 165, 5-18 (2008)
- Potter, David Stone, Prophecy and history in the crisis of the Roman Empire: a historical commentary on the Thirteenth Sibylline Oracle, Cf. Chapter 3 (1990)
- Poulson, Frederick. Dephi Gleydenhall, London (1920)
- Rohde, Erwin, Psyche: The Cult of Souls and the Belief in Immortality among the Greeks, trans. from the 8th edn. by W. B. Hillis, Routledge & Kegan Paul, London, (1925); reprinted by Routledge (2000); full text in English
- West, Martin Litchfield, The Orphic Poems, Oxford: Clarendon Press ISBN 0-19-814854-2 (1983)