context: The Director is in communication with angels (or eldila, as author C.S. Lewis terms them in his space trilogy), and they are helping him head off the final conquest of Earth by the fallen angels. Should the bad angels succeed, “Bad men, while still in the body, still crawling on this little globe, would enter that state, which, heretofore, they had entered only after death [i.e., Hell], would have the diuturnity and power of evil spirits.”
definition: Long duration; lastingness.
definition source: dictionary.com
quotation source: That Hideous Strength by C.S. Lewis