A Plutarch dialogue at Delphi asking why oracles once common across Greece have grown silent, weighing daemons, vapors, and physics as causes.
De Defectu Oraculorum ("On the Obsolescence of Oracles") is one of the philosophical dialogues collected in Plutarch's Moralia. It is set at Delphi, where the narrator's friends -- Demetrius the grammarian, fresh from Britain, and Cleombrotus of Sparta, back from Egypt and the Red Sea -- meet other locals including Ammonius the philosopher. Their conversation, prompted by an old myth about eagles or swans meeting at the earth's "navel" at Pytho, turns into an inquiry into why so many oracular shrines across the Greek world have fallen silent or diminished, leaving only Delphi and a couple of others still active.
The speakers work through several competing explanations. One line of argument invokes daemons -- intermediate beings between gods and mortals who inhabit and animate oracles -- and asks whether oracles fail because these daemons die, move on, or are punished, since daemons, unlike the gods, are not necessarily immortal. Another line, argued at length near the end by the narrator, grounds prophecy in physical causes: an exhalation or "vapor" rising from the earth at Delphi that periodically waxes and wanes in potency, interacting with the natural mantic faculty of the Pythia (the priestess) much as wine or the pipe's music affects different people differently. The dialogue explicitly frames this as a search for the "twofold cause" of any event -- the divine/rational principle and the material/physical mechanism -- criticizing both those who cite gods without addressing mechanism and materialist "natural philosophers" who ignore the divine mover entirely.
The piece matters as a rare window into how an educated, pious Greek intellectual of the Roman imperial period (1st-2nd century CE) tried to reconcile traditional religion with contemporary natural philosophy, without simply debunking the oracles or accepting them uncritically. It also documents concrete Delphic ritual detail -- the pre-consultation sacrifice, the testing of the victim's tremors, the chastity requirements for the Pythia -- that survives from firsthand practice at the shrine.
“Some say, Terentius Priscus, that two eagles—or, as others tell it, two swans—flying from the outer limits of the earth toward the center, met each other at Pytho, at the place called the navel of the earth”
— De Defectu Oraculorum · read this chapter →
“There is no need to inquire about matters there and puzzle over the dimming of the oracles here, when we see the eclipse of virtually all of them except one or two.”
— De Defectu Oraculorum · read this chapter →
“since every coming-into-being has a twofold cause, the very ancient theologians and poets chose to attend to the superior one, uttering that common refrain applied to all things: 'Zeus the beginning, Zeus the middle, and from Zeus all things have their being'”
— De Defectu Oraculorum · read this chapter →
“I think, then, that the vapor does not remain in the same condition invariably at all times, but has certain periods of relaxation and, again, of intensity”
— De Defectu Oraculorum · read this chapter →
“For neither does wine always affect the drinker in the same way, nor the pipe always produce the same enthusiastic effect; rather, at one time the same people are stirred into Bacchic frenzy less, at another more”
— De Defectu Oraculorum · read this chapter →
It is a Plutarch dialogue set at Delphi in which several speakers try to explain why most Greek oracular shrines had gone silent by their own time, while Delphi still functioned. The discussion moves from myth to the idea of daemons inhabiting shrines to a physical theory of a prophetic vapor rising from the earth.
The dialogue offers no single verdict but weighs multiple causes: daemons who staff and empower oracles may die, depart, or be removed; and the earth's prophetic exhalation at a site like Delphi can weaken or strengthen over time, changing how well the Pythia can be inspired. Plutarch insists both a divine and a material cause are needed together.
The speakers treat daemons as beings between gods and mortals who are not necessarily immortal, and consider that oracles could fall silent because the daemon associated with a shrine dies, moves elsewhere, or is punished, rather than because the god withdraws.
The dialogue describes an exhalation or vapor from the earth that varies in intensity over time and combines with the Pythia's own inborn mantic sensitivity, compared to how wine or pipe-music affects different drinkers or listeners unevenly. Priests first test the sacrificial victim's tremors to judge whether conditions are right.
The main voices are the narrator (a stand-in for Plutarch), Demetrius the grammarian returning from Britain, Cleombrotus of Sparta returning from Egypt and the Red Sea, Ammonius the philosopher, and a young man named Philip who raises questions about the sun and Apollo.
Yes. De Defectu Oraculorum is one of the philosophical-religious dialogues collected in Plutarch's Moralia, distinct from his better-known biographical Lives.
Moralia: Ad Principem Ineruditum · Moralia: Adversus Colotem · Moralia: Amatoriae Narrationes · Moralia: Amatorius · Moralia: An Recte Dictum Sit Latenter Esse Vivendum · Moralia: An Seni Respublica Gerenda Sit · Moralia: An Virtus Doceri Possit · Moralia: An Vitiositas Ad Infelicitatem Sufficia · Moralia: Animine An Corporis Affectiones Sint Piores · Moralia: Apophthegmata Laconica · Moralia: Aquane An Ignis Sit Utilior · Moralia: Bruta Animalia Ratione Uti