The Pythia (/ˈpɪθiə/;[1] Ancient Greek: Πυθία [pyːˈtʰi.aː]) was the name of the high priestess of the Temple of Apollo at Delphi who also served as its oracle, also known as the Oracle of Delphi.

The name Pythia is derived from Pytho, which in myth was the original name of Delphi. Etymologically, the Greeks derived this place name from the verb πύθειν (púthein) "to rot", which refers to the sickly sweet smell of the decomposition of the body of the monstrous Python after she was slain by Apollo.[2]

The Pythia was established at the latest in the 8th century BC,[3] (though some estimates date the shrine to as early as 1400 BC[4][5][6]), and was widely credited for her prophecies uttered under divine possession (enthusiasmos) by Apollo. The Pythian priestess emerged preeminent by the end of the 7th century BC and continued to be consulted until the late 4th century AD.[7] During this period, the Delphic Oracle was the most prestigious and authoritative oracle among the Greeks, and she was among the most powerful women of the classical world. 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, Nepos, Ovid, Pausanias, Pindar, Plato, Plutarch, Sophocles, Strabo, Thucydides, Shakespeare, and Xenophon.

Nevertheless, details of how the Pythia operated are scarce or missing entirely, as authors from the classical period (6th to 4th centuries BC) treat the process as common knowledge with no need to explain. Those who discussed the oracle in any detail are from 1st century BC to 4th century AD and give conflicting stories.[8] One of the main stories claimed that the Pythia delivered oracles in a frenzied state induced by vapours rising from a chasm in the rock, and that she spoke gibberish which priests interpreted as the enigmatic prophecies and turned them into poetic dactylic hexameters preserved in Greek literature.[9] This idea, however, 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.[10] Herodotus, writing in the fifth century BC, describes the Pythia speaking in dactylic hexameters.[11][12]

De Boer's research caused him to propose ethylene as a

De Boer's research caused him to propose ethylene as a gas known to possess this sweet odor.[69] Toxicologist Henry R. Spiller stated that inhalation of even a small amount of ethylene can cause both benign trances and euphoric psychedelic experiences. Other effects include physical detachment, loss of inhibitions, the relieving of pain, and rapidly changing moods without dulling consciousness. He also noted that excessive doses can cause confusion, agitation, delirium, and loss of muscle coordination.[70]

Anesthesiologist Isabella Herb found that a dose of ethylene gas up to 20% induced a trance in which subjects could sit up, hear questions and answer them logically, though with altered speech patterns, and they might lose some awareness and sensitivity in their hands and feet. After recovery, they had no recollection of what had happened. With a dose higher than 20%, the patients lost control over their limbs and might thrash wildly, groaning and staggering. All these hallucinogenic symptoms match Plutarch's description of the Pythia, whom he had witnessed many times.[71]

During 2001, water samples from the Kerna spring, uphill from the temple and now diverted to the nearby town of Delphi, yielded evidence of 0.3 parts per million of ethylene.[72] It is likely that in ancient times, higher concentrations of ethylene or other gases emerged in the temple from these springs.[73][74]

Frequent earthquakes produced by Greece's location at the clashing intersection of three tectonic plates could have caused the observed cracking of the limestone, and the opening of new channels for hydrocarbons entering the flowing waters of the Kassotis. This would cause the admixture of ethylene to fluctuate, increasing and decreasing the potency of the drug. It has been suggested that the waning of the Oracle after the era of Roman Emperor Hadrian was due in part to a long period without earthquakes in the area.