1. Über das E in Delphi

Moreover, as Plato said, when an oracle was given that they should double the size of the altar at Delos (a task requiring the highest skill in geometry), it was not this that the god was enjoining, but he was urging the Greeks to study geometry.

[Plutarch, Moralia 386 E]


2. Über den Genius des Sokrates

[...] we felt so yet more when on our return from Egypt a party of Delians met us in Caria and requested Plato, as a geometer, to solve a problem set them by the god (1) in a strange oracle. The oracle was to this effect: the present troubles of the Delians and the rest of the Greeks would be at an end when they had doubled the altar at Delos.

As they not only were unable to penetrate its meaning, but failed absurdly in constructing the altar (for upon doubling all four sides they discovered to their surprise that in their ignorance of the progression from which the linear double is obtained they had produced by this increase a solid eight times as large), they called on Plato for help in their difficulty.

Plato, recalling the Egyptian, replied that the god was rallying the Greeks for their neglect of education, deriding, as it were, our ignorance and bidding us engage in no perfunctory study of geometry; for no ordinary or near-sighted intelligence, but one well versed in the subject, was required to find two mean proportionals, that being the only way in which a body cubical in shape can be doubled with a similar increment in all dimensions.

This would be done for them by Eudoxus of Cnidus (2) or Helicon of Cyzicus (3); they were not, however, to suppose that it was this the god desired, but rather that he was ordering the entire Greek nation to give up war and its miseries and cultivate the Muses, and by calming their passions through the practice of discussion and study of mathematics, so to live with one another that their intercourse should be not injurious, but profitable.

[Moralia 579 A-D]

1) Apollon
2) Eudoxos von Knidos (ca. 391/0 – 338/7 v.u.Z.), einer der bedeutendsten griechischen Mathematiker und Astronomen
3) Helikon von Kyzikos, sagte die Sonnenfinsternis vom 12. Mai 361 v.u.Z. voraus