Plutarch, Theseus
Bernadotte Perrin, Ed.

After the death of Aegeus, Theseus conceived a wonderful design, and settled all the residents of Attica in one city, thus making one people of one city out of those who up to that time had been scattered about and were not easily called together for the common interests of all, nay, they sometimes actually quarrelled and fought with each other. [2] He visited them, then, and tried to win them over to his project township by township and clan by clan. The common folk and the poor quickly answered to his summons; to the powerful he promised government without a king and a democracy, in which he should only be commander in war and guardian of the laws, while in all else everyone should be on an equal footing. [3] Some he readily persuaded to this course, and others, fearing his power, which was already great, and his boldness, chose to be persuaded rather than forced to agree to it. Accordingly, after doing away with the townhalls and council-chambers and magistracies in the several communities, and after building a common town-hall and council-chamber for all on the ground where the upper town of the present day stands, he named the city Athens, and instituted a Panathenaic festival. [4] He instituted also the Metoecia, or Festival of Settlement, on the sixteenth day of the month Hecatombaeon, and this is still celebrated. Then, laying aside the royal power, as he had agreed, he proceeded to arrange the government, and that too with the sanction of the gods. For an oracle came to him from Delphi, in answer to his enquiries about the city, as follows:— [5]

Theseus, offspring of Aegeus, son of the daughter of Pittheus,
Many indeed the cities to which my father has given
Bounds and future fates within your citadel's confines.
Therefore be not dismayed, but with firm and confident spirit
Counsel only; the bladder will traverse the sea and its surges.

‘Bladder may be submerged; but its sinking will not be permitted.’