Bibliomania: Greek oral tradition

In ancient Greece communications were sent orally. Therefore, most civil affairs, including contracts and treaties required strong verbal skills.

From  Manual of Classical Literature, by Johann Eschenburg:

The earliest written laws were those of Draco. Even inscriptions upon public monuments and tombs were but seldom in the first ages. There is scarcely a trace in Homer of written orders or dispatches, everything of the kind being transacted by oral messages...

The writing of books seems to have commenced in the time of Pisistratus and Solon, and its first fruits were perhaps merely the recording of traditional poetry. It is not an improbable supposition that the poetry of Homer was not committed to writing by himself, but that this was first done at a later period, and with the insertion of many passages not belonging to it.

Education was also transmitted orally. Wise men were  

distinguished for their knowledge and thereby enjoyed a conspicuous rank and influence in the state. These men delivered orally their doctrines and precepts, which in later periods were collected and recorded. In the first ages, when the compass and sum of all known attainments was not very great, many and various kinds were united in one individual, who was at once theologian, physiologist, speculative and practical philosopher, statesman, lawgiver, poet, orator, and musician. The subsequent division and separation of the branches of knowledge contributed to its advancement and perfection...