De Defectu Oraculorum

(The persons taking part in the conversation are: Lamprias, Demetrius, Cleombrotus, Ammonius, Philip, Didymus, and Heracleon.)

The story is told, my dear Terentius Priscus, that certain eagles or swans, flying from the uttermost parts of the earth towards its centre, met in Delphi at the omphalus, as it is called; and at a later time Epimenides of Phaestus put the story to test by referring it to the god and upon receiving a vague and ambiguous oracle said,

Now do we know that there is no mid-centre of earth or of ocean; Yet if there be, it is known to the gods, but is hidden from mortals.

Now very likely the god repulsed him from his attempt to investigate an ancient myth as though it were a painting to be tested by the touch.