The Fiction of Ideas

While reading 'The Left Hand of Darkness,' the story starts out with space travel to an alien planet. Two astronauts try to bring two civilizations on that plant together for some kind of peace. 

The idea of space travel and alien plants/civilizations aren't fiction, the worlds the author creates for this story are. The creation adds to the alien planets we haven't discovered yet. The author also creates the planets religion and spirituality, which could be fiction but with so many possibilities in the universe, it's always possible that something similar exists.