We all know that books burn — yet we have the greater knowledge that books cannot be killed by fire. People die, but books never die. No man and no force can abolish memory. No man and no force can put thought in a concentration camp forever. No man and no force can take from the world the ideas that embody man’s eternal fight against tyranny of every kind. In this war, we know, books are weapons.
Franklin Delano Roosevelt (1882-1945) American lawyer, politician, statesman, US President (1933-1945)
Letter (1942-04-23), “Message to American Booksellers Association,” Annual Banquet (1942-05-06), Astor Hotel, New York City
(Source)
The letter was delivered with a speech by Archibald MacLeish (appointed by Roosevelt as Librarian of Congress, 1939-1944) titled "A Free Man's Books." This was shortly after FDR named April 17 as "Victory Book Day".
This quotation was turned into a poster by S. Broder, published by the US Office of War Information in 1942.