"For I suppose if Lacadaemon were to become desolate, and the temples and the foundations of the public buildings were left, that as time went on there would be a strong disposition with posterity to refuse to accept her fame as a true exponent of her power...Whereas if Athens were to suffer the same misfortune, I suppose that any inference from the appearance presented to the eye would make her power to be twice as great as it is." Thucydides I.10 trans. Crawley
Luckily for the Spartans' glory, they had the Athenian historian to tell posterity in indelible ink how powerful they had been when time inevitably overtook them. Many other peoples have been less lucky. Think about how little you probably know or care about the fall of the Roman Empire. You reckoned it had something to do with Caligula and Nero, those tyrants hymned by the famous historians Tacitus and Suetonius. Think again. It happened four centuries later when all the great minds were in the church, which is why you don't know about it... History relies on its historians. No event, no matter how significant, really catches posterity's imagination without someone with an attractive style to write about it. Thucydides goes to a lot of effort to show how important the conflict he writes about is, but the truth is, that in the context of all human history, its chief distinction is that it had him to write about it.
Which got me thinking about how little we live in such a historically blessed era. Not only do we lack a great historian, we don't write much literature of survival value, or even create many material objects likely to make it into the coffee table books of the distant future. Plato's philosophy survived Byzantine taste, in the main because of its entertaining and immediate style, ditto Francis Bacon's essays or Chaucer surviving changing literary fashions in subsequent centuries.
To me it looks as though it's more likely to be television that anyone is still holding on to in a few centuries' time, a medium which like classical tragedy or Eizabethan drama is actually intended to be enjoyed (a word to underline in relation to contemporary theatre, for example) by everyone from the most educated to the least. What we should spend more time doing is thinking about what will survive us and what will not...I think we'd be surprised what proves to be ephemeral.