A letter from Jane Welsh Carlyle concludes, "Pray read all this unto yourself and burn the letter." A scholar has added this gloss: "Such an injunction is one of the surest methods of guaranteeing that a letter will not be burned."
Fragments of the works of Sappho have come down to us because someone in antiquity, wanting to get rid of papyrus copies of Sappho's poetry, threw them into the trash in the Egyptian city of Oxyrhynchus, where archaeologists found them. Certain works by Archimedes have survived only because his words were scraped off by medieval scribes; the scribes re-used the parchment for a sacred book, whose sanctity ensured its survival into an age when a different kind of eyes could tease out the underlying original. The mosaics of Hagia Sofia, in Istanbul, were inadvertently spared degradation when the Ottoman Turks covered them with plaster. The early Christian writer Irenaeus spent a lifetime denouncing heretical books; many of the books were lost (burned), and yet the ideas survived through extensive quotation in his own fiery writing.
The ultimate weapon against ideas is indifference, not opposition; with "repressive tolerance", or the capacity of a laissez-faire society to bury ideas by not reacting to them. (via Techdirt)