A dialogue at Delphi asking why the letter E was dedicated to Apollo, moving from arithmetic to a metaphysics of divine changeless Being.
De E Delphos ("On the E at Delphi") is one of the Pythian dialogues in Plutarch's Moralia, framed as a conversation Plutarch recalls having heard at the Delphic shrine and now writes up for his friend Sarapion. The occasion is a puzzle every visitor to Delphi noticed: three golden or bronze letters E hung beside Apollo's temple, and no one agreed on why. The dialogue stages several rival explanations offered by named speakers -- Ammonius the philosopher, his brother Lamprias, the priest Nicander, Theon, and the Pythagorean-minded Eustrophus -- each proposing a different key to the riddle.
The explanations escalate in ambition. Nicander and the Delphic priests say E abbreviates the conditional question every oracle-seeker asks ("if..."), making it a monument to the logic of conditional propositions -- the very tool needed to parse ambiguous prophecy. Theon defends logic itself as the god's favorite art, tying the letter to the structure of demonstration. Eustrophus then reinterprets E as the numeral five (E was the Greek sign for 5), launching a long Pythagorean excursus: five as the union of the first even and odd numbers, the five musical concords, the five Platonic solids and elements, the five senses, Homer's five-part division of the cosmos, and Plato's fivefold schemes in the Sophist and Philebus. Ammonius then overturns the whole numerical approach: E is not a number or a particle but a complete utterance, "Thou art" (ei), the human being's address to a god who alone truly exists.
That final move opens into the dialogue's philosophical core, a meditation on Heraclitean flux versus Platonic Being: mortal nature never stays the same instant to instant, so humans cannot truly say "I am," while the god's eternity has no before or after, only a single unmoving "now." Ammonius closes by pairing Apollo (unity, purity, the changeless) against a shadow-figure of dissolution and death, and by reconciling "Thou art" with Delphi's other famous inscription, "Know Thyself": one salutes the god's eternal being, the other reminds mortals of their own instability. The piece matters as a compact record of how educated Greeks under the early Empire folded arithmology, logic, and Platonist metaphysics into the interpretation of a religious symbol.
“Since, then, philosophy is concerned with truth, and the light of truth is demonstration, and the starting point of demonstration is the conditional, it is fitting that the power which holds this together and produces it should have been consecrated by wise men to the god who most of all loves truth.”
— De E Delphos · read this chapter →
“For it is not possible, according to Heraclitus, to step twice into the same river; nor is it possible to touch a mortal substance twice in the same state, but by the sharpness and speed of its change 'it scatters and gathers again'”
— De E Delphos · read this chapter →
“but being one, he has filled up ‘forever’ with a single ‘now,’ and only what exists in this way is truly real—not having come to be, nor being about to be, nor having begun, nor going to cease.”
— De E Delphos · read this chapter →
“For the god, as each of us approaches him here, greets us, as it were, with the words 'Know thyself' — which is no less a greeting than 'Hail.' And we, in turn, answering the god, say 'Thou art,'”
— De E Delphos · read this chapter →
“only the number five, and six along with it, when multiplied by themselves that many times over, reproduce and preserve themselves. For six times six is thirty-six, and five times five is twenty-five.”
— De E Delphos · read this chapter →
It is a dialogue set at Delphi about why three letters E were dedicated beside Apollo's temple. Several speakers propose different answers -- that E marks the conditional 'if' central to oracles and logic, that E is the numeral five with Pythagorean significance, and finally that E is the utterance 'Thou art,' addressed to a god whose being is eternal and unchanging.
Plutarch narrates a conversation he recalls from a visit during Nero's time, featuring the philosopher Ammonius, his brother Lamprias, the Delphic priest Nicander, a companion named Theon, and Eustrophus the Athenian, each offering a rival theory about the letter E.
Eustrophus argues five is the first number produced by combining the first even and odd numbers, and shows it uniquely reproduces itself under multiplication and addition; he ties it to the five musical concords, five Platonic solids and elements, and five senses, treating this self-generating pattern as fitting Apollo's nature.
Following Heraclitus, Ammonius argues that a person changes continuously from infancy through old age, so that 'the man in his prime perishes when the old man comes to be' -- nothing about a mortal stays fixed long enough to justify the verb 'to be.' Only a timeless god, existing in a single eternal 'now,' can rightly be addressed as 'Thou art.'
The dialogue reports theologians who saw Apollo and Dionysus as two phases of one god's transformation -- Apollo as fire and unity, honored with the ordered paean, and Dionysus as the god's dispersal into the manifold world, honored with the wilder dithyramb, following what they describe as a three-to-one ratio of the year.
De E Delphos belongs to the Moralia, Plutarch's large collection of essays and dialogues distinct from his biographical Parallel Lives; it is one of several 'Pythian dialogues' set at Delphi, where Plutarch served as a priest of Apollo.
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