The title is a reference to a passage from John Milton's Paradise Lost:
Innumerable force of Spirits armed, That durst dislike his reign, and, me preferring, His utmost power with adverse power opposed In dubious battle on the plains of Heaven And shook his throne. What though the field be lost? All is not lost—the unconquerable will, And study of revenge, immortal hate, And courage never to submit or yield: And what is else not to be overcome?[2]