Sure, I was being a bit harsh on ancient philosophy there. But the point I was trying to make was that it really wasn't "knowledge" of the kind the OP seemed to be thinking of. It wasn't scientific. The loss of it (if it had been lost) wouldn't have led to a stagnation of scientific or social progress. It was all about how many Henads emanate from the One, and that kind of thing. People often talk as if the closure of the philosophical schools, and their replacement with Christian theological institutions, was the replacement of enlightened free thought with religious obfuscation. My point was that the philosophical schools and the Christian institutions were really pretty much the same, except that one lot were pagan and the other were Christian. It's a mistake to see the philosophical and literary institutions of antiquity as somehow rational and scientific while those of the "Dark Ages" were not. To the extent that the Roman Empire promoted learning, it did so not by providing libraries and universities but by giving a certain class of people the leisure and security to pursue their own private studies. Learning declined with the fall of Rome - to the extent that it did - not because the Library of Alexandria got ransacked but because there was no longer such a large class of leisured aristocrats with nothing better to do than read Cicero to each other. And they were, in any case, effectively replaced by a growing class of monks who had nothing better to do than to make copies of Cassian and Gregory the Great. Plus ça change and so on.