Also -- and critically -- none of the simple denizens of Cypress Corners are aware that they live aboard a spaceship in flight. The doorway to another ship compartment -- a long connecting corridor to another dome and another society -- is sealed off and decorated with fearsome graffiti which reads: "Beyond is Death."
Jeremiah (Sterling Hayden), leader of the sect, has also stated that he who goes beyond the door "abandons all hope...never to return," equating the "outside" of Cypress Corners with a Biblical Hell. It is, in his words, a “bottomless pit.” In Cypress Corners, knowledge equates to “evil.”
Thematically, "Voyage of Discovery" has something vital to say about life here on Earth, and I enjoyed how the metaphor (or subtext) was created and carried out.
This is a powerful comment on life on Earth. We wage wars, we fight over ideology and religion...but meanwhile, what becomes of the Earth itself? There's an environmental and human message in The Starlost that -- in the Age of Global Climate Change -- feels even more relevant today, perhaps.