secondary world n.

What really happens is that the story-maker proves a successful ’sub-creator'. He makes a Secondary World which your mind can enter. Inside it, what he relates is 'true' : it accords with the laws of that world. You therefore believe it, while you are, as it were, inside. The moment disbelief arises, the spell is broken ; the magic, or rather art, has failed. You are then out in the Primary World again, looking at the little abortive secondary World from outside.

To make a Secondary World inside which the green sun will be credible, commanding Secondary Belief, will probably require labour and thought, and will certainly demand a special skill, an elvish craft.

The best science-fiction writers create…Secondary Worlds and take us inside. They may do it, as Hal Clement has done in his best stories, Robert Heinlein in most of his, and Arthur C. Clarke and Frank Herbert with notable success, by building their worlds as carefully as an architect-builder would do his work.

Meaning is transferred from Primary World into Secondary (and vice versa), but the forms or shapes that meaning takes belong to the Secondary World and operate by its rules, not the rules of ordinary nature.

Instead of fantastic elements merely intruding upon their home territory, the protagonists of portal fantasies are physically removed to unfamiliar ground, into a secondary world.