When you are talking about millions of works, you need to approach it statistically.
That we have some works preserved does not mean that we are succeeding at preserving works in general. Nor is the fact that we have books preserved by previous generations a guarantee that the same books will be preserved by current and future generations.
So one way to think about this is that society has a big junkyard into which it throws documents. And sometimes, people do some archeological digging and reconstruct portions of some documents or bring them to light and popularize them, bringing them out of the junkyard, with a bias towards those documents that reconstruct whatever fashions are happening in that society.
That does not mean that the society as a whole is preserving documents well, even though you will always have some ancient texts available, and people are still mining the junkyard.
Moreover once we move to information stored online in the present climate of account deletion and deplatforming, we are again reconstructing the ingredients for a dark ages as mass deletion of online data is a lot easier than burning individual books. Many of the manuscripts we have were literally pulled out of ancient trashheaps or were written over by other texts. That's a lot less likely to happen with modern technologies.
You weren't originally making a statistical point, you said:
>Absolutely nothing can last in a liberal society that believes moral progress is possible
Which is clearly not true.
In any case, toward the more general claim that this post is making, which I will summarize as "Authoritarian societies are statistically better at preserving works in general" this is also demonstrably not true in the wide statistical sense. They are just as likely (if not more) to deliberately discard works that disagree with the general ethos of that society. Heresy is not really a big deal in a liberal society, but it will get some books burned and practitioners slaughtered (reducing social transmission of ideas) in a autocratic theocracy, for example.
Huh? Pounding your fists on the table is not, you know, an argument. That not everything is deleted after 50 years is not proof that something can last permanently.
> In any case, toward the more general claim that this post is making, which I will summarize as "Authoritarian societies
That's a complete misunderstanding of the post, which contrasts traditional societies with liberal societies, by changing the subject to authoritarian societies. As if this was the only choice.
Authoritarian societies are not the opposite of liberal societies. In fact authoritarian societies -- e.g. communist and nazi societies or other societies in which individuals are micromanaged -- only came into existence in the 20th Century when the technology for mass micromanagement became possible. And whatever words you use to descibe authoritarian societies, "preserving tradition" is not one of them. These are big book burning, history-rewriting societies because they try to address the issue of social reproduction by the fist of centralized top-down control that monitors and micro-manages every aspect of life. Human beings are not compatible with that type of control, which is why authoritarian societies don't last very long -- the Russian czars lasted a thousand years whereas communism lasted only 70. And people were much more free under the czars than under communism, because the czars never tried to control every aspect of social life, and never needed to setup networks of gulags, or a vast secret police force, or party functionaries throwing people in prison for skipping work without a doctor's note.
There is the old saying "the right talks about authority, the left talks about control". For a society to be able to preserve knowledge, it must develop long lasting institutions and a culture that reveres the past and seeks to preserve it. Therefore while you need a cultural respect for authority, you cannot actually have a centralized system of social control. So you need basics like "honor your father and your mother" to be taught in churches and other civil institutions, but you cannot have a world in which political meetings decide which author is going to be erased from history today or whether so-and-so is allowed to attend university because their parents were class enemies.
That we have some works preserved does not mean that we are succeeding at preserving works in general. Nor is the fact that we have books preserved by previous generations a guarantee that the same books will be preserved by current and future generations.
So one way to think about this is that society has a big junkyard into which it throws documents. And sometimes, people do some archeological digging and reconstruct portions of some documents or bring them to light and popularize them, bringing them out of the junkyard, with a bias towards those documents that reconstruct whatever fashions are happening in that society.
That does not mean that the society as a whole is preserving documents well, even though you will always have some ancient texts available, and people are still mining the junkyard.
Moreover once we move to information stored online in the present climate of account deletion and deplatforming, we are again reconstructing the ingredients for a dark ages as mass deletion of online data is a lot easier than burning individual books. Many of the manuscripts we have were literally pulled out of ancient trashheaps or were written over by other texts. That's a lot less likely to happen with modern technologies.