Orphans Of The Sky

Fix-up consisting of the novelette "Universe" and the novella "Common Sense" (1941). First published in 1963.

Hugh Hoyland must convince a starship civilization that can't remember or conceive of life outside the ship they inhabit that a universe does exist. With the help of the outcast mutants from the upper decks of the ship, Hugh sets out to expose the truth and thus change their civilization forever...