From the introduction to Ursula K. LeGuin's The Left Hand of Darkness:
The artist deals with what cannot be said in words. The artist whose medium is fiction does this in words. The novelist says in words what cannot be said in words.
If you replace the concept of fiction with the concept of theology, LeGuin (an atheist) has unwittingly given a fairly eloquent definition of the task of theology. The introduction itself is a rather fascinating treatise on science fiction, and the novel is an excellent read.