I would imagine that while literacy and the use of written documents is not a prerequisite for "civiliation" or "progress", it would seem to be mandatory for the development, maintenance and consistency of complex systems - such as the legal system - over time. Interesting proposition, though!

Yes, CK, there is no denying that now but I'd like to go back for a visit (time machine needed here, of course) to the oral times of Homer and imagine this...Odysseus shooting the breeze with King Alcinous....

"As for me, I know nothing
So completely delightful as a land where people are filled
With good humor, and those that feast in the halls sit quietly
At tables covered with good things to eat and listen
To the songs of a poet, while the wine-bearer draws wine from the bowl
And fills the goblets of all. This seems to me
The finest thing in the world.

BOOK IX, The Odyssey of Homer